Download ILX Lightwave LDT-5910 Temperature Controller

I N S T R U C T I O N hIANUAL
hIODEL LDT-5910
THERMOELECTRIC TEhIPERATURE CONTROLLER
ILX Lightwave Corporation
34368 East Frontage Road
Bozeman, Montana, U.S.A.
(406) 586- 1244
WARRANTY
I L X LIGHTWAVE CORPORATION warrants this instrument to be f r c e f r o m dcfccts
i n material a n d workmanship f o r one year f r o m the d a t e of shipment. D u r i n g
the w a r r a n t y period we will repair or replace the unit, a t o u r option, without
charge.
Limitation
This w a r r a n t y does not apply to fuses, lamps, batteries, defects caused by abuse,
a n y modifications, or to use of the product f o r which i t was not intended.
This w a r r a n t y is i n lieu of all other warranties, expressed or implied, including
a n y implied w a r r a n t y of merchantability or fitness f o r a n y particular purpose.
I L X Lightwave Corporation shall not be liable f o r a n y incidental, special, or consequential damages.
If a problem occurs, please notify ILX Lightwave Corporation a n d thoroughly
describe t h e n a t u r e of the problem a n d give the model a n d serial numbers. You
will be given prompt attention, service information, a n d r e t u r n instructions.
Returning a n Instrument
Before r e t u r n i n g a n instrument, obtain a r e t u r n authorization n u m b e r f r o m t h e
factory. T h e instrument should be shipped i n the original packing carton or one
t h a t will provide equal protection. Shipping damage is not covered by this warranty. Send t h e instrument, transportation pre-paid to the factory, referencing
the r e t u r n authorization number. Repairs will be made a n d t h e i n s t r u m e n t will
be returned, transportation pre-paid. Repairs a r e w a r r a n t e d f o r t h e remainder of
the original w a r r a n t y or f o r 90 days, whichever is greater.
Claims f o r Shipping Damage
When you receive the instrument inspect i t immediately f o r a n y d a m a g e or shortages
on t h e packing list. If the instrument is damaged immediately f i l e a claim w i t h
the carrier. T h e f a c t o r y will supply you with a quotation f o r estimated costs of
repair. You must negotiate a n d settle with the carrier f o r the a m o u n t of damage.
Table of Contents
C H A P T E R 1 .G E N E R A L I N F O R M A T I O N . . . . . . . . . . . . . . . . .
1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . .
P r o d u c t Overview . . . . . . . . . . . . . . . . . . . . . . . .
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . .
Available Options a n d Accessories
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1.1
1.2
1.3
1.4
C H A P T E R 2 .O P E R A T I O N . . . . . . . . . . . . . . . . . . . . . . . .
2.1 I n t r o d u c t i o n . . . . . . . . . . . . . . . . .
2.2 Installation
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2.3
A C Power Considerations . . . . . . . . .
2.4
Tilt-Foot Adjustment . . . . . . . . . . .
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2.5
R a c k Mounting
2.6 LDT-5910 F r o n t Panel Controls . . . . . . . .
2.7
Power . . . . . . . . . . . . . . . . . .
2.8
M a i n Control K n o b . . . . . . . . . . . .
2.9
Auto . . . . . . . . . . . . . . . . . . .
2.10
Actual Temp . . . . . . . . . . . . . . .
2.11
Set T e m p . . . . . . . . . . . . . . . . .
2.12
Lock . . . . . . . . . . . . . . . . . . .
2.13
Output On . . . . . . . . . . . . . . . .
2.14
G P I B Remote/Local Switch . . . . . . . .
2.15 P a r a m e t e r Set-Up . . . . . . . . . . . . . . .
2.16
Select . . . . . . . . . . . . . . . . . .
2.17
Set . . . . . . . . . . . . . . . . . . .
2.18
Limit . . . . . . . . . . . . . . . . . .
2.19
Gain . . . . . . . . . . . . . . . . . . .
2.20
C a l i b r a t i o n Constants - C1, C 2 a n d C 3 . . .
2.21 Back P a n e l . . . . . . . . . . . . . . . . . .
2.22
Back Panel Connections . . . . . . . . .
2.23
G r o u n d i n g Considerations . . . . . . . . .
2.24
C u r r e n t Switch . . . . . . . . . . . . . .
2.25 O p e r a t i n g Instructions . . . . . . . . . . . .
2.26
Warm U p a n d E n v i r o n m e n t a l Considerations
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2.27
G e n e r a l O p e r a t i n g Procedure
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C H A P T E R 3 . GPIB/IEEE-488 BUS C O N T R O L . . . . . . . . . . . . . . .
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3.1 I n t r o d u c t i o n . . . . . . . . . . . .
3.2 Capabilities . . . . . . . . . . . .
. . . .
3.2 P r e p a r a t i o n f o r Bus Control
3.3 A n O v e r v i e w of Remote Programming
3.4
C o m m a n d Set . . . . . . . . . .
3.5
R e m o t e Programming Procedure .
3.6
Input Syntax . . . . . . . . . .
3.7 Device D e p e n d a n t Commands . . . .
3.8
D a t a E n t r y Commands . . . . .
3.9
Sct Point Commands . . . . . .
3.10
O u t p u t Control Commands . . .
3.1 1
Lock Commands . . . . . . . .
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3.12
3.13
3.14
3.15
3.16
3.1 7
3.18
3.19
3.20
3.21
3.22
Display Commands . . . .
G e t Commands . . . . . .
P u t Values . . . . . . . .
T e r m i n a t o r Commands . .
Clear Command . . . . .
Self Test Command . . . .
Control Mode Command . .
Service Requests . . . . . . .
T h e Serial Poll Register a n d the
I n t e r f a c e Messages . . . . . .
Example Programs . . . . . .
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S R Q Mask
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C H A P T E R 4 .T H E O R Y O F OPERATION . . . . . . . . . . . . . . . . .
4.1 Introduction . . . . . . . . . . . . .
4.2 Power Supply Board . . . . . . . . .
4.3
I n t e r n a l Power Supplies . . . . . .
4.4 M a i n B o a r d . . . . . . . . . . . . .
4.5
Constant C u r r e n t Source . . . . .
4.6
Input Buffer . . . . . . . . . . .
4.7
D i f f e r e n c e Amplifier . . . . . . .
4.8
Digitally Controlled G a i n Stage . .
4.9
Integrator . . . . . . . . . . . .
4.10
Summing Amplifier . . . . . . .
4.1 1
C u r r e n t Limiting . . . . . . . . .
4.12
C u r r e n t Limit D / A . . . . . . . .
4.13
C u r r e n t Limit Condition Sensing . .
4.14
Voltage Controlled Current Source .
4.15
Voltage Limit Condition Sensing . .
4.16
Set Point Control D / A . . . . . .
4.17
Precision Voltage Reference . . . .
4.18
A / D Convertor . . . . . . . . . .
4.19
Microprocessor . . . . . . . . . .
4.20
Memory . . . . . . . . . . . . .
4.2 1
Serial Interface . . . . . . . . . .
4.22
L a t c h e d Parallel 1 / 0 Port . . . . .
4.23 Display Board . . . . . . . . . . . .
4.24
Display Driver . . . . . . . . . .
4.25
Latched Parallel 1 / 0 Port . . . . .
4.26
L E D Drivers . . . . . . . . . . .
4.27 GPIB Interface Board . . . . . . . . .
4.28
Microprocessor a n d Memory . . . .
4.29
Optical Isolators . . . . . . . . .
4.30
Serial Interface . . . . . . . . .
4.3 1
GPIB Interface
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C H A P T E R 5 .MAINTENANCE . . . . . . . . . . . . . . . . . . . . . .
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5.1 Overview . . . . . . . . .
5.2 Calibration . . . . . . . . .
5.3
Recommended Equipment
5.4
Environmental Conditions
5.5
Warm-up . . . . . . . .
5.6 Calibration Adjustments . .
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5.7
Manual Resistance Calibration . . . . . . .
Manual Current Limit Calibration . . . . . .
Resistance Calibration Over the GPIB Bus . .
C u r r e n t Limit Calibration Over the GPIB Bus
Fuse Replacement . . . . . . . . . . . . . . .
Line Voltage Selection . . . . . . . . . . . . .
Disassembly . . . . . . . . . . . . . . . . . .
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41
CHAPTER 6 . OPTIONAL MODEL 1227 GPIBIIEEE-488 I N T E R F A C E . . . .
45
6.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . .
6.2 Specifications . . . . . . . . . . . . . . . . . . . . . . . . . .
6.3 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
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Appendix A .T h e Steinhart-Hart Equation . . . . . . . . . . . . . . . . .
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Appendix B . Sensing Current and Thermistor Selection . . . . . . . . . . .
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Appendix C . Schematic Diagrams . . . . . . . . . . . . . . . . . . . . .
60
5.8
5.9
5.10
5.1 1
5.12
5.13
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List of Figures
2-1
2-2
2-3
3-1
3-2
4- 1
4-2
5-1
A-1
B-1
LDT-5910 Front Panel Layout . . . . . . .
LDT-5910 Back Panel Layout . . . . . . .
Back Panel Connector . . . . . . . . . . .
Address Selection Switch Settings . . . . .
GPIB Remote Operation Diagram . . . . .
Functional Block Diagram of LDT-59 10 . .
Functional Block Diagram of 1227 Interface
AC Voltage Selection . . . . . . . . . . .
Thermistor Resistance verses Temperature .
Thermistor Temperature Range . . . . . .
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5
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Copyright. 1987. ILX Lightwave Corporation
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58
CHAPTER 1
GENERAL INFORhlATION
1.1
Introduction
T h i s m a n u a l explains how to operate a n d m a i n t a i n the LDT-5910 Thcrmoclcctric
T e m p e r a t u r e Controller a n d optional model 1227 GPIBIIEEE-488 I n t c r f a c e . T h i s
section gives a d e t a i l e d overview of the LDT-5910. If you w a n t to get s t a r t e d
using t h e LDT-5910 r i g h t a w a y , s k i p to C h a p t e r 2 (Operation).
1.2
Product Overview
T h e LDT-5910 is a microprocessor-based, precision thermoelectric t e m p e r a t u r e controller designed f o r t e m p e r a t u r e control of laser diodes, dctcctors a n d o t h e r tcmpcra t u r e sensitive devices. T h e LDT-5910 c a n be used f o r laser d i o d e testing, laser
d i o d e f r e q u e n c y stabilization, I R detcctor cooling, a n d to d c t e r m i n e t h e c h a r a c t e r istics of electronic devices. T h e LDT-5910 combines high analog stability w i t h
the versatility of a microprocessor-based instrument. T h e i n t e r n a l microproccssor
controls t h e o p e r a t i o n of t h e LDT-5910 a n d p e r f o r m s t h e non-linear conversion
of thermistor resistance to t e m p e r a t u r e based on t h r e e user d e f i n e d constants.
You c a n c o n f i g u r e t h e LDT-5910 to operate w i t h a wide v a r i e t y of thermistor
t e m p e r a t u r e sensors a n d T E modules. T h e model 1227 GPIB/IEEE-488 i n t e r f a c e
allows remote p r o g r a m m i n g a n d completely a u t o m a t e d control of t h e LDT-5910.
F e a t u r e s of t h e LDT-5910 include:
I n t u i t i v e f r o n t panel layout
L a r g e a n d easy-to-read green L E D display
Display resolution of 0.1 degree C e n t i g r a d e
O u t p u t c u r r e n t limit control to safely opcratc all T E coolers
C o n f i g u r a b l e f o r most thermistors
O u t p u t will supply 4.6 amps
Actual, Set a n d A u t o display modes
Set t e m p e r a t u r e lock
GPIB/IEEE-488 i n t e r f a c e available
Booster modules c a n be a d d e d to e x t e n d t h e o u t p u t power
1.3 Specifications
Output
O u t p u t Type:
Bipolar constant c u r r e n t source.
Compliance Voltage:
8 Volts a t 1 A, 7 Volts a t 2 A, 6 Volts a t 3 A.
Maximum C u r r e n t Output:
4.6 Amps.
Maximum O u t p u t Power:
15 Watts typical.
C u r r e n t Limit Control Range:
C u r r e n t Limit Accuracy:
Temperature Control
Temperature ~ a n g e ' :
-50 " C to > l o 0 " C with typical 10 K thermistor
Resolution a n d ~ c c u r a c y ~ :
Temperature
0°C
20°C
50 " C
Short T e r m stability3:
0.01 " C or better.
Scnsor Type:
2-wire thermistor.
Usable Resistance Range:
0 to 450 K ohm typical.
Sensing Current:
10 uA or 100 u A (user sclcctable).
Calibration:
Thermistors a r e calibrated by storing three constants of the S t e i n h a r t - H a r t equation, listed
below, i n internal non-volatile memory.
l / ~ = ( C l * l O - ~ ) + ( C 2 * 1 0 - ~ )~( l)n+ ( ~ 3 * 1 0 - ~ )R( l) n~ .
Resolution
kO.1 " C
20.1 " C
f0.2 " C
Display
Display Type:
4 digit green L E D display.
Maximum Reading:
9999 mA, 999.9 " C.
Resolution:
Accuracy
k0.2 " C
k0.2 " C
k0.2 " C
kl.O mA, kO.1 "C.
General
Power Requirements:
105-125 or 210-250 VAC(jumper sel ectable) 50-60 Hz.
Size:
88 mm x 212 m m x 269 mm (3.5" x 8.4" x 10.6").
Temperature Range:
Operating: 0 to 50 " C, Storage: -40 to 70 " C.
Warmup:
1 hour to rated accuracy.
1.
2.
Temperature control range depends primarily on the type of thermistor and T E module used. The range can be
extended higher and lower by selecting appropriate components. See Appendix B for more details.
Accuracy figures quoted are typical for a 10 K ohm thermistor and 100 uA source current setting. Accuracy figures
are relative t o calibration standard. Both resolution and accuracy are dependent on the user defined configuration
of the instrument.
3. Short term temperature stability is a strong function of the thermal environment of the thermistor and T E module.
Room air currents in particular can easily cause fluctuations of 0.1 C in an exposed mounting configuration.
1.4 Available Options a n d Accessories
The following options a n d accessories a r e available f o r the LDT-5910.
DESCRIPTION
MODEL N U M B E R
GPIB/IEEE-488 interface
1227
O u t p u t power booster module
5310
R a c k mount flange kit
302
R a c k mount, 1/2 width
filler panel kit
Enclosure interlocking kit
112
T h e 1227 i n t e r f a c e permits GPIB bus control of the LDT-5910 f o r automated test
a n d measurement applications. Chapter 6 describes this option i n detail.
T h e LDT-5910 enclosure c a n be rack mounted by itself or interlocked w i t h other
I L X Lightwave, X-series instruments. T h e accessories listed above a r e f o r rack
mounting a n d interlocking these instruments.
1.5 Your Comments
I L X Lightwave Corporation is committed to making the best laser diode instrumentation available anywhere. T o serve you best, we need your ideas a n d comments on
ways we can improve our products. We invite you to contact us a t a n y time with
your suggestions.
CHAPTER 2
OPERATION
2.1
Introduction
This chapter describes how to install, program a n d operate the LDT-5910. It is
divided into f i v e sections covering installation, f r o n t pancl controls, proccdurcs
f o r programming the LIMIT, G A I N a n d constants C1, C2, a n d C3, the back pancl
connections, a n d normal operating procedures.
2.2
Installation
2.3
AC Power Considerations
You c a n configure t h e LDT-5910 to operate a t line voltages f r o m 105 to 125 VAC
or 210 to 250 VAC. Before using the LDT-5910 check t h a t the voltage printed
on t h e rear panel matches the power-line voltage supplied i n your area. If i t is
necessary t o reconfigure the i n p u t voltage range r e f e r to chapter 5 (Maintenance).
WARNING
T o avoid electrical shock hazard, connect the instrument only to
properly earth-grounded, 3-prong receptacles. Failure to observe
this precaution can result in injury or loss of life.
2.4
Tilt-Foot Adjustment
T h e LDT-5910 has f r o n t legs t h a t extend to make i t easier to view t h e L E D display
T o use them, place t h e LDT-5910 on a stable base a n d rotate the legs d o w n w a r d
until they lock i n t o position.
2.5
Rack Mounting
T h e LDT-5910 may be rack mounted by installing a rack mount f l a n g e o n one
side of t h e enclosure a n d a half width filler panel on the other side. Alternately,
two X-series enclosures will interlock side-by-side, with a pair of rack m o u n t
flanges, f o r r a c k mounting as one unit. All rack mount accessory kits contain
detailed mounting instructions. R e f e r to Section 1.4 f o r applicable rack m o u n t
accessory part numbers.
2.6
LDT-5910 Front Panel Controls
T h e following sections describe the f r o n t panel
erally these controls a r e simple to operate. T h e
intentionally a bit a w k w a r d to use so t h a t their
changed. Figure 2-1 shows the LDT-5910 f r o n t
controls on the LDT-5910. Gensetup parameters, however, a r e
values a r e not inadvertently
panel a n d its controls.
DISPLAY MODE SWITCHES
AND INDICATORS
TEMPERATURE LOCK MODE
SWITCH AND INDICATOR
DISPLAY
MAIN CONTROL KNOB
POWER
OFFION
SWITCH
OUTPUT
OFFION
SWITCH
GPIBIIEEE-488
REMOTE MODE
INDICATOR AND
LOCAL SWITCH
PARAMETER SET
SELECTOR SWITCH
LIMIT CURRENT
DISPLAY INDICATOR
THERMISTOR CONSTANTS
DISPLAY INDICATORS
PARAMETER DISPLAY
SELECTOR SWITCH
FEEDBACK LOOP GAIN
DISPLAY INDICATOR
FIGURE 2-1
LDT-5910 FRONT PANEL LAYOUT
2.7
Power
With t h e LDT-5910 connected to a n AC power source, pressing the Power o f f / o n
switch will supply power to the instrument a n d start the power-up sequence. All
the f r o n t panel LEDs will light. After approximately threc scconds the display
will read t h e a c t u a l temperature in degrees centigrade a n d the instrument will bc
in Auto mode.
2.8 Main Control Knob
T h e main control knob is a precision ten t u r n potentiometer t h a t adjusts t h e
instrument set temperature. This knob is also used to change the instrument sct
point temperature setup parameters. T u r n i n g this knob to the right increases
the value on t h e display.
2.9
Auto
When i n Auto mode the display shows the actual thermistor temperature until
you t u r n the m a i n control knob. T h e LDT-5910 senses t h a t you have t u r n e d thc
knob a n d "knows" t h a t you want to i n p u t a new set temperature. T h e instrument
displays the new set point temperature f o r three seconds a n d then r c t u r n s to
displaying the a c t u a l temperature. T h e Auto mode allows you to accurately change
the set point temperature a n d quickly see how your device is responding. T h e
Auto button has a toggling action; press it to enter a u t o mode a n d press i t again
to exit a u t o mode.
2.10 Actual Temp
When this button is pressed the LDT-5910 displays t h e actual thermistor temperature
a n d the L E D on the button lights to indicate t h a t the actual temperature is displayed.
2.11 S e t Temp
T h i s button, w h e n pressed, displays the temperature set point a n d t h e L E D on
the button lights to indicate t h a t the set tempcrature is displayed. T u r n t h e
main control k n o b to enter a new set point.
2.12 Lock
When you press t h e f r o n t panel LOCK button t h e LDT-5910 stores t h e c u r r e n t
set temperature i n memory a n d disables the main control knob. T h e L E D lights
to show t h a t t h e u n i t is in lock mode. T h e value stays in memory even if the
LDT-5910 is s h u t o f f . If you use the same set point temperature d a y a f t e r d a y
you will appreciate the LDT-5910 LOCK feature. T o release the LDT-5910 f r o m
lock mode, press the lock button again.
Caution
Turn t h e output o f f before releasing t h e unit from lock mode.
If t h e main control knob position h a s changed the LDT-5910 will
read t h e new knob position and try to control the temperature
to t h a t setting.
2.13 Output On
This button switches the output of the LDT-5910 on. T h e o f f / o n button has a
toggling action. If the output is o f f , pressing it will t u r n the o u t p u t on a n d vice
versa. T h e L E D above the indicator button lights when the output is active.
When the o u t p u t is off it is safe to connect or remove sensitive devices f r o m
the LDT-5910 even though power is on. T h e output is off when power is f i r s t
applied to the instrument.
T h e output o f f / o n button also indicates when a thermal limit condition occurs. I n
the rare event t h a t excessive heating occurs i n the LDT-5910 output stage (or i n
a n attached booster module) the output of the LDT-5910 is turned off a n d thc
output o f f / o n L E D flashes. T h e output automatically turns back on when the
output stage cools down.
2.14 G P I B Remote/Local Switch
This button r e t u r n s the instrument to local control when it is in remote mode with
the optional Model 1227 GPIB/IEEE-488 interface installed. Any command sent
to the LDT-5910 via the GPIB bus automatically places the instrument in remote
mode a n d the REMOTE L E D lights. All the f r o n t panel controls, except power
a n d GPIB REMOTE/LOCAL, a r e disabled a n d will only operate remotely. Pressing
the LOCAL button will return the instrument to local mode a n d all the f r o n t
panel controls will operate.
If no command has been sent over the GPIB bus, the LDT-5910 is i n LOCAL mode
a n d its address will be displayed when you press this button. If the instrument
is in remote mode a n d a local lockout (LLO) mcssage has bccn sent, the host has
complete control of the LDT-5910 a n d the LOCAL button has no effect. For
more information on GPIB programming, read chapter 3.
2.15 Parameter Set-Up
2.16 Select
T h e select f u n c t i o n displays the setup parameters so you can review or change
their values to configure the LDT-5910 f o r your thermistor a n d T E cooler. Press
the SELECT button a n d the limit will be displayed until you release the button.
T h e value will show f o r three seconds before the LDT-5910 returns its previous
state. Press t h e Select button again to sequence the display through G A I N , C1,
C2 a n d C3. T h e sections below describe each of these values a n d how to change
them.
2.17 S e t
This button, along with the main control knob, is used to change the setup parameters: LIMIT, GAIN, C1, C2 a n d C3. Sequence to the setup parameter you
wish to change a n d hold the SELECT button in to continuously display this value.
Simultaneously press a n d hold in the SET button. Now t u r n the main control
knob until the new value is displayed. Release the Set button to store the parameter i n non-volatile memory. T h e instrument will automatically go i n t o lock
mode to save t h e present set point when the SET button is pushed.
2.18 Limit
T h e limit f u n c t i o n limits the output current so t h a t t h e LDT-5910 does not provide
more c u r r e n t t h a n your device can safely handle. T o rcad the limit, press the
select button u n t i l the L E D by the LIMIT is lit a n d the display will show the
value of the LIMIT (in mA). T o change the limit, sequence to thc LIMIT value
a n d hold i n t h e SELECT a n d the SET button. T u r n the main control knob until
the new value is on the display a n d then release the SET button. T h e LIMIT
should be entered in milliamperes, e.g., 1 a m p would be entercd as 1000 mA.
T h e LDT-5910 will supply as much current as i t can, u p to a c u r r e n t limit set
point of 4600 mA, to control the temperature as quickly as possible. T h e LDT-5910
can supply u p t o 10 A with the optional power booster module installed.
T h e LIMIT L E D also indicates two special conditions, c u r r e n t a n d voltage limiting.
If the output is c u r r e n t limited, as when the o u t p u t is f i r s t t u r n e d on, t h e LIMIT
L E D will flash slowly (2 times/second). If the o u t p u t is voltage limited, if f o r
instance no load is connected, the LIMIT L E D will flash faster (4 times/second).
2.19 Gain
T h e gain f u n c t i o n sets the analog feedback gain which determines how f a s t the
actual temperature reaches a n d settles to the set point temperature. If t h e gain
is set too low t h e T E cooler will take longer to reach the temperature set-point.
If it is set too high the actual temperature will overshoot a n d may cycle a r o u n d
the set temperature. T h e gain setting depends on t h e type of T E cooler t h a t
you a r e using, b u t we c a n give guidelines f o r selecting the proper gain. Set the
gain to its lowest value a n d increase it until the actual tempcrature oscillates
a r o u n d the set temperature. T h e n reduce the gain one increment. T o set the gain,
sequence to t h e G A I N value a n d hold in t h e SELECT a n d the S E T button. T u r n
the main control knob until the new value is displayed a n d then release t h e S E T
button. T h e f e e d b a c k loop gain can be selected in increments of 1, 3, 10, 30,
100 a n d 300.
2.20 Calibration Constants
-
C1, C2 and C3
These a r e t h e constants of Steinhart-Hart equation t h a t you enter to calibrate
the LDT-5910 f o r d i f f e r e n t thermistors. Appendix A contains a n explanation of
the Steinhart-Hart equation, the values of these constants f o r some common thermistors a n d a computer program to determine these values f o r a n y thermistor.
T o read a constant press the SELECT button until i t sequences to C1, C2 or C3.
T h e L E D next to the constant will light. T o change t h e value, press the SELECT
a n d the SET buttons a n d t u r n the main control knob until the correct number is
displayed. Release the S E T button to store the new value i n non-volatile memory.
2.21 Back Panel
T h e back panel contains the thermistor input, TE module output, A C power e n t r y
connector, fuse, a n d a thermistor source current set switch. When the optional
model 1227 GPIBIIEEE-488 interface is installed, t h e back panel additionally contains
the s t a n d a r d GPIB bus connector a n d the GPIB address selector switch. T h e
back panel is shown in f i g u r e 2-2.
THERMISTUR
INPUT
G P I B BUS
CONNECTOR
G P I B ADDRESS
FUSE
SELECTOR SWITCH
I
TE MODULE
OUTPUT
POWER ENTRY
CONNECTOR
THERMISTOR
SOURCE CURRENT
SET SWITCH
AUXILIARY
INPUT/UUTPUT
CUNNECTOR
2.25 Operating Instructions
2.26 Warm Up and Environmental Considerations
Operate the LDT-5910 a t a n ambient temperature between 0 a n d 50 degrees centigrade. Storage temperatures should be in the range -40 to 70 C. To achieve
the rated accuracy let the LDT-5910 w a r m u p f o r about 1 hour before use.
2.27 General Operating Procedure
You c a n operate the LDT-5910 in several modes. T h e following operating procedure
is applicable f o r most common use.
a.
Plug t h e LDT-5910 into a n AC power source supplying the correct voltage
a n d f r e q u e n c y f o r your unit (refer to the rear panel f o r the correct
ratings).
b.
T u r n on t h e LDT-5910. T h e output stage will be o f f a t power-up.
c.
Check the setting of the GAIN, LIMIT a n d C1, C2, a n d C 3 to insure t h a t
they a r e compatible with the equipment you a r e using. R e f e r t o sections
2.15 to 2.20 if you need to change them.
d.
Press t h e Set T e m p button a n d check the set point temperature. If i t
requires changing refer to the section above.
e.
T u r n t h e o u t p u t on by pressing the o u t p u t on button
f.
T h e LDT-5910 will automatically control the temperature to the set point.
CHAPTER 3
GPIBIIEEE-488 BUS CONTROL
3.1
Introduction
When the model 1227 GPIB/IEEE-488 intcrface is installed a n d the instrumcnt is
connected to a host computer, the LDT-5910 can be used as a n automated tcmpera t u r e controller a n d temperature recorder f o r test measurement applications.
3.2 Capabilities
T h e model 1227 GPIB/IEEE-488 interface allows GPIB/IEEE-488 bus control of the
LDT-5910. All of the features accessible f r o m the f r o n t panel a n d some advanced
features can be accessed via the interface bus. Information can also be read by
the host computer a n d printed or stored. Other features include:
A concise a n d simple command set
Full talk/listen capability
Full serial poll capability, with bit-maskable S R Q
Selectable output terminators
Full local/remote capability including LOCAL L O C K O U T
Resistance Control Mode controls to a set resistance
Support f o r the following interface messages: R E N , DCL,LLO, G T L and
SDC
3.2
Preparation for Bus Control
T o use the LDT-5910 remotely, you will need to install a n IEEE-488 i n t e r f a c e
adapter in your host computer. These adapters a n d support software a r e available f r o m several manufacturers a n d can be installed i n most computers. This
manual assumes that you have a basic knowledge of the GPIB/IEEE-488 interface
bus a n d how to use it f o r instrument control. This section also assumes t h a t
you a r e f a m i l i a r with the controls on the LDT-5910. Read Chapter 2 again if
you need more details on how to operate the LDT-5910.
Install the 1227 interface using the procedure outlined i n Chapter 6. Prepare the
LDT-5910 f o r bus control using the following procedure:
1.
T u r n o f f t h e power to the LDT-5910/1227 a n d set the GPIB/IEEE-488
interface address with the DIP switches on the back panel. T h e switch
settings a r e shown in f i g u r e 3-1. You can choose a n y address f o r the
LDT-591011227 but this address should be unique, i.e., d i f f e r e n t t h a n a n y
other instrument connected to the bus.
Switch Positions
Address 1 2
3
4
5
Switch Positions
2
3
4
5
Address 1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
-Not Allowed-
FIGURE 3-1 ADDRESS SELECTION SWITCH SETTINGS
3.3
2.
Plug the GPIBIIEEE-488 bus cable into the LDT-5910/1227 rear panel
connector a n d secure it with the plug-mounted screws.
3.
T u r n o n t h e LDT-591011227 a n d press the local button to display the
selected IEEE-488 instrument address on the f r o n t panel display.
An Overview of Remote Programming
T h e block diagram, f i g u r e 3-2 shows the flow of d a t a f r o m the LDT-5910/1227 to
the host computer (the controller). Each block represents a register, b u f f e r etc,
contained in the LDT-5910. T h e input b u f f e r receives d a t a f r o m t h e IEEE-488
bus. T h e o u t p u t b u f f e r receives d a t a f r o m the blocks to its l e f t a n d sends d a t a
to the IEEE-488 bus. T h e serial poll register is a separate b u f f e r t h a t gets the
attention of the controller i n special conditions.
Information is transferred between blocks by device dependant commands. For
example, a Put command takes a number f r o m the i n p u t b u f f e r a n d stores it in
the internal memory of the LDT-5910. Likewise the Get command gets the contents of the LDT-5910 internal memory a n d copies it into the output b u f f e r .
-
Programming commands, like print a n d read i n BASIC or F O R T R A N , transfer the
information f r o m the input or output buffers to the controller. T h e following
simple program provides a n example of how the LDT-5910 is controlled by the
host computer. T h e exact programming statements you will need to use will depend
on the programming language a n d IEEE-488 interface card t h a t you a r e using. This
program instructs the LDT-5910 to display actual thermistor temperatures a n d
then reads out t h e current display. T h e LDT-5910 is assumed to be a t GPIB
address 1.
100
110
120
130
-
-
3.4
Print @1:"D2"
I n p u t @l:A$
Print A$
End
Command S e t
There a r e two types of commands that you can use with the LDT-5910/1227 a n d
the GPIB bus. Messages t h a t only the LDT-5910/1227 understands a r e called
device d e p e n d a n t commands. Messages t h a t a r e common to a n y instrument on
the GPIB bus a r e called interface messages. T h e device dependant commands a r e
summarized i n Table 3.1 a n d described i n sections 3.7 to 3.17. T h e LDT-5910/1227
also responds to a number of interface messages to participate in IEEE-488 bus
communication. T h e i n t e r f a c e messages a r e summarized in Table 3.5.
MICROPRUCESSOR MEMORY
SET POINT
Tnnnmnn
TEMPERATURE
v
A
RESISTANCE
SET-UP PERAMETERS
Rnnnmnn
G1 , P1
CURRENT LIMIT
G2
GAIN
G3
C1
7
A
C2
V
C3
CALIBRATION PERAMETERS
CAL-RlO
G4
, P2
, P3
, P4
INPUT
BUFFER
G5 , P5
, P6
G7 , P7
G6
w
A
CAL-R100
3,
CAL-CL
G9 , P 9
USER DEFINED MESSAGE
- GO
A
I
OUTPUT
BUFFER
e
3
SRQ
REGISTER
DISPLAY
INSTRUMENT MUDE
CUNTROL
--
DO
LO
DO
WO
ZO
YO
-
-
, 01
, L1
-
-
D5
-
Y2
,n
W5
OUTPUT CONTROL
LOCK CUNTROL
DISPLAY MODE
OUTPUT TERMINATOR CUNTRUL
SELF TEST , CLEAR
REMOTE/LOCAL MODE CUNTRUL
FIGURE 3-2 GPlB REMOTE OPERATION DIAGRAM
TABLE 3.1
LDT-591011227 DEVICE DEPENDENT COMMAND SET
Set Point Commands
Put Values
Tnnn
Rnnn
Adjusts the set temperature to
n n n n n n C.
Adjust the set Resistance to
n n n n n n K ohm.
Data Entrv Commands
Nnnn
Numeric d a t a
'aaa'
Alphanumeric data
PO
P1
P2
P3
P4
P5
P6
P7
P8
P9
PI0
Not Used
Put current limit (mA)
P u t gain
PutC1
Put C2
Put C3
Put CAL-R10 value
Put CAL-R100 value
Put CAL-C1 value
Put user defined message
Put SRQ mask
Outuut Control Commands
Terminator Commands
00
01
T u r n t h e output o f f .
T u r n t h e output on.
Enable C R L F EOI (default)
Enable C R L F only
Enable C R EOI only
Enable CR only
Enable L F EOI only
Enable L F only
Enable EOI only
Disable a l l output
terminators
Lock Commands
LO
L1
Disables set temp. lock
Enables set temp. lock
Displav Commands
DO
D2
D3
D4
D5
Blank t h e display
Actual Temperature
Set Temperature
Auto display mode enable
Resistance display mode
Clear Commands
*
Device Clear
Self Test Command
Get Commands
ZO
GO
G1
G2
G3
G4
G5
G6
G7
G8
G9
G10
Get
Get
Get
Get
Get
Get
Get
Get
Get
Get
Get
error status
c u r r e n t limit
gain
C1
C2
C3
CAL-RlO value
CAL-R 100 value
CAL-CL value
user defined message
SRQ Mask
Begin Self Test
Control Mode Commands
YO
Y1
Y2
Enable LOCAL mode
Enable REMOTE mode
Enable LOCAL L O C K O U T mode
3.5 Remote Programming Procedure
To program the LDT-591011227 send it a n ASCII string of characters made of
one or more device d e p e n d a n t commands. The commands set the operating parameters such a s t h e temperature set point, o u t p u t c u r r e n t limit, etc.. A simple
example of a command string would be:
" 0 1 D2 T-2.0"
In this example the LDT-5910/1227 o u t p u t is t u r n e d on,
the display is configured to read actual temperature and
the set point tcmperature would be set to -2.0 C.
In t h e examples in this manual, device dependent commands a r e shown encloscd
in quotation marks, as they would be entered i n BASIC or other programming
languages. T h e commands a r e also separated by spaces. T h e spaces a r e f o r clarity
a n d may be omitted.
Explanation
Example
"* G 9 T10.0"
T h i s is t h e same a s "*G9T10.OW
When the LDT-5910/1227 receives a command string i t is placed in remote mode
a n d then each command in the string is executcd sequentially.
T o read the display simply send a n instruction to read ASCII d a t a f r o m t h e 1227
interface. When the LDT-5910/1227 receives t h e instruction, t h e contents of the
interface o u t p u t b u f f e r a r e transmitted, as a string of ASCII characters, over the
bus to the controller. Specific programming examples a r e given a t t h e e n d of
this chapter.
3.6
Input S y n t a x
This section describes the syntax rules f o r constructing device d e p e n d e n t comm a n d strings used to control the LDT-5910/1227. A command s t r i n g is f o r m e d b y
a series of i n d i v i d u a l commands followed by a terminator.
T h e LDT-5910/1227 accepts alphabetic characters in either upper or lower case.
Commands m a y be strung together into a n ASCII string u p to 30 characters long.
A n y character beyond t h i r t y is truncated. Certain characters a r e ignored a n d
may be included a n y w h e r e in a command string to make i t easier to read. These
ignored characters a r e shown below:
Space
Back slash
I1
11
v'/*l
A command string must be concluded with one or more i n p u t terminators. Processing of the command string begins when the f i r s t i n p u t terminator is received.
Acceptable i n p u t terminators a r e shown below:
Carriage r e t u r n
Line f e e d
EOI
[CRl
[LFl
w11
ASCII (0 13)
ASCII (010)
Illegal commands a n d unrecognized characters (eg, 0 3 ) will set the s o f t w a r e error
flag but a r e otherwise ignored. T h e following characters a r e known to produce
error codes:
Examplcs of correct a n d incorrect Command strings a r e given in Tablc 3.2.
Table 3.2 Command String Examples
Correct Command Strings
Upper or lower case alphabetic characters may be used.
These command strings a r e identical a n d will t u r n the
output on a n d set the control temperature to 30 C.
0 1/R4.5 L 1[EOI]
Spaces (and back slashes) may be used within the command
string f o r clarity. This command turns the o u t p u t on,
the set point is controlled to 4.5 K ohms a n d the set
point lock is activated.
Incorrect Command Strings
7'45.34 @ 01 [EOI]
T h e "@" is a n unrecognized charactcr. When the "0"is
encountered the software error status bit (error 32) is
set a n d processing continues normal1 y. T h e LDT-59 10/ 1227
controls to 45.34 C a n d the output is t u r n e d on.
TO T0.34 T L1 [CR]
T h e operator couldn't decide which temperature to set.
A numeric entry was expected following the t h i r d "T".
T h e software error status bit (error 32) will be set but
processing will continue normally beginning with L1 command.
0 1 B3 R1O.O1l [CR]
"B3" is a n unknown command a n d this sets software error
status bit. Processing will continue normally w i t h the
next command. In this case, the output will be t u r n e d
on a n d the LDT-5910/1227 will control to 10.01 1 K ohm.
T1.00E-1 D2 [CR]
Although "1.00E-1" is often used as scientific notation to
mean 0.100 the LDT-591011227 does not recognize this
f o r m of notation. In this case the "E-1" is interpreted
as a n unrecognized command a n d the s o f t w a r e e r r o r status
bit (error 32) will be set. T h e D2 command will change
the display mode so the LDT-591011227 displays actual
temperature.
3.7 Device Dependant Commands
3.8 Data Entry Commands
Nnnnnnn - Numeric Entry
N numeric e n t r y where "nu is one of the following:
{signed or unsigned integer)
(signed or unsigned real number)
T h e N command enters the numeric values f o r subsequent Put commands. T h e
interpretation of the numeric value depends o n which put command it is used
with. T h e decimal is "free floating" f o r real numbers, i.e., it can be placed
anywhere b u t the LDT-5910/1227 will only control to its internal range a n d
accuracy.
Exantple
Explanation
Put a value of 1.234 into the calibration constants
memory i n the LDT-5910/1227 as the new value
of the constant C2.
"Nl000 P I "
'aaaaaaa'
-
Sets the c u r r e n t limit to 1000.
Alphanumeric Data Entry
This command is used with the P9 command to put a n y message into non-volatile
memory i n the LDT-5910. U p to sixteen characters of alphanumeric d a t a may
be entered with this command. T h e alphanumeric information must be surrounded with the single quote sign (ASCII 39). This message can be r e a d w i t h the
Get command, G9.
Example
"'This is a test' P9"
3.9
Explnrtation
Places the message "This is a test" into the nonvolatile memory.
Set Point Commands
Tnnnnnn
This command changes the Set Temperature i n the LDT-5910. Notice t h a t
there a r e six digits (nnnnnn) f o r this command. T h e set-point accuracy a n d
range depend on the thermistor used a n d the source current setting. Appendix
B discusses the limits of range a n d accuracy f o r typical thermistors.
Example
E x planntioil
"T-2.0"
Set the Set Temperature to -2.0 C.
"T200."
T h e LDT-5910/1227 will try to control the o u t p u t to 200
C but will be limited by the available o u t p u t c u r r e n t a n d
the accuracy of the set-point D / A convertor.
Rnnnnnn
This control makes the LDT-5910/1227 control to a resistance value instead of
a temperature value. This function is not accessible f r o m the f r o n t panel.
T h e resistance is entered in K ohms. T h e range a n d accuracy is limited as
shown i n T a b l e 3.3.
Example
Explnization
T h e LDT-5910/1227 will control to a Resistance of
10.2 K ohm.
"R 10.2"
Table 3.3 Thermistor Range a n d Accuracy
10 uA
0 to 450K ohms
0 to 45 K ohms
Range
Resolution
lOOuA
0.2K ohms
0.02K ohms
3.10 Output Control Commands
T h e Output control commands toggle the LDT-5910/1227 output o f f or on. T h e
o u t p u t must be t u r n e d on f o r the LDT-5910/1227 to control to a set temperature
or resistance.
Exnnzple
Expla ftatioir
" 0 1 T30.33"
T u r n s the output on a n d controls the temperature to
30.33 C.
*'OO"
T u r n s the output o f f .
3.11 Lock Commands
T h e lock commands lock the set temperature or set resistance into memory so
t h a t it will not be lost when the power is turned o f f . T h e last number received
with the set temperature or set resistance command will be the number t h a t is
stored i n memory. When the lock is active, other set temperature or set resistance
commands will be ignored.
Example
Explanation
Controls to a resistance of 8K, locks this value
into memory a n d ignores the set temperature
command.
The first set temperature is ignored ( i f the
temperature is already locked), the lock is
disabled a n d the new set resistance (9K) is
entered.
3.12 Display Commands
T h e Display commands allow you to select what the LDT-5910/1327 will display
on its f r o n t panel display. T h e display will indicate whatever it last displayed,
before going to remote mode, until you send it a command to display something
different.
DO
- Blank
t h e Display.
This command is used f o r best performance when high IEEE-488 Interface
Data rates a r e required.
D2
-
Actual Temperature
T h e display will indicate the actual temperature in degrees Centigrade.
D3
-
S e t Temperature
T h e Set Temperature will be displayed.
D4
-
Auto Display Mode
This command enables the Auto display mode. In remote operation t h e display
will indicate t h e actual temperature until a new temperature is sent to the
LDT-5910. T h e n the new set temperature will be displayed f o r three seconds
before reverting to the actual temperature again.
D5 - Resistance Display Mode
This command enables the display of the measured resistance, in K ohms, of
the thermistor connected to the LDT-5910. This is only available in T h e remote
mode a n d is useful when controlling to a set resistance.
Example
Expln~~ntiolz
"R8 d 5 01"
T h e LDT-5910/1227 controls to a resistance of 8K,
the displays indicates resistance a n d the o u t p u t is
turned on.
"t30.2 d 3 01"
T h e set temperature is 30.2 C a n d the display reads
this temperature. T h e output is turned on.
3.13 Get Commands
The get commands place information into the LDT-5910/1227 o u t p u t b u f f e r f o r
the host computer. Each Get command loads the output b u f f e r with a n ASCII
output string. T h e get commands must precede a n y computer language commands,
e g , BASIC commands like read or input, because the information must be loadcd
into the output b u f f e r of the LDT-5910/1227 before it can be read. A f t e r the
b u f f e r is read, a n y subsequent read commands will return the number displayed
on the LDT-5910 f r o n t panel display.
GO Command
-
G e t Error Status
This command reads the status of the internal software error byte i n the LDT
-5910. T h e ASCII string generated by the GO command may be read back over
the bus by executing a read immediately a f t e r sending the GO command. If
the GO command is sent with a string of commands, a n y errors set by previous
commands in the string will set the appropriate error bit. A f t e r loading the
ASCII string into the interface output b u f f e r , the software command error
f l a g is reset.
Two digits a r e sent back that represent the appropriate error code if a n error
has occurred. A summary of the error codes a r e listed below.
00
01
02
04
08
16
32
No Error
A / D Overrange
Temperature Calculation Unsuccessful
C u r r e n t Limit
Voltage Limit
Thermal Limit
Software Error
If there is no error a zero is returned. If there was more t h a n one e r r o r
condition t h e number sent back equals the sum of the errors codes. Some
example o u t p u t strings a r e given here:
Example
Explamtiorl
If a 10 is returned then the temperature calculation
was unsuccessful a n d a voltage limit condition occurred. T h e error byte is reset to zero.
"t-999g0"
G1
-
This set temperature command will cause t h e current
to be limited which will set error number 04. If no
other errors have been recorded, the 04 will be
returned by the GO command. If another error was
present before the t-999 command, say a n A / D Overrange condition, a f i v e (05) will be returned.
G e t current limit
T h e current limit is placed in the output b u f f e r
G2
Get gain
T h e gain will be placed in the output b u f f e r . T h e gain will be one of the
accepted gains (1,3,l OJO, 100,300).
G3
G4
G5
Get C1
Get C2
Get C3
T h e Get C l , C 2 or C3 commands will move values, f o r a n internally stored
thermistor calibration constant, to the output b u f f e r .
G6
G7
Get CAL-R 10 value
Get CAL-R100 vaiue
This moves t h e internal resistance scaling factors, f o r the 10 u A a n d 100 u A
internal resistance calibration, into the output b u f f e r . R e a d chapter 5 f o r a n
explanation of what these scaling factors represent.
G8
Get CAL-CL vaiue
This moves t h e internally stored current limit calibration scaling f a c t o r into
the o u t p u t b u f f e r . R e a d chapter 5 f o r a n explanation of w h a t this calibration
scaling f a c t o r represents.
G9
Get User Defined Message
T h e G 9 command loads the output b u f f e r with the user d e f i n e d message t h a t
has been stored in the non-volatile memory. T h e messagc is stored i n t h e
LDT-5910's memory with the P9 command.
G I 0 Get S R Q Mask
T h i s command copies the present S R Q mask into the o u t p u t b u f f e r . T h e S R Q
mask is placed i n t o memory with the P10 command. Service Requests, the
serial poll register a n d the S R Q mask a r e discussed i n sections 3.18 a n d 3.19.
3.14 Put Values
T h e put commands can configure the LDT-5910/1227 a n d select the operating
mode by entering "putting" information in the appropriate registers. T h e P U T
commands a r e described i n this section.
PI-Put Current Limit (mA)
Enters t h e c u r r e n t limit f o r the LDT-5910.
Example
"N1000 P1"
Explanation
Sets t h e c u r r e n t limit t o 1000 mA.
P2
- Put
Gain
Enters the gain. T h e gain must be one of the acceptable gains f o r the instrument. i.e. 1, 3, 10, 30, 100 or 300. Any other number will generate a n error
code.
Example
"N300 P2"
P3
P4
P5
-
Explanation
Sets the gain to 300.
Put C1
Put C2
Put C3
These put commands store values, of the constants Cl,C2 or C3 f o r the Steinhart-Hart equation, in the LDT-5910's non-volatile memory.
Example
"N1.434 P5"
Expla~zatio~i
Puts the value of 1.434 into memory f o r C3.
P6 Put CAL-R10 Value
P7-Put CAL RlOO Value
T h e P6 a n d P7 commands enter a n input calibration scaling f a c t o r used to
calibrate t h e resistance values. T h e input must be a f i v e digit integer. For
more information about this calibration constant refer to Chapter 5.
Example
Explanatiorl
Puts the scaling factor 10337 into memory f o r
the 10 uA calibration constant.
P8
-
Put Calibration CL Value
T h e P8 command inputs the current limit calibration scaling f a c t o r to calibrate
the Current Limit. T h e i n p u t must be a f i v e digit integer. For more i n f o r m a tion about this calibration constant refer to Chapter 5.
Example
"N11237 p8"
Explanation
Puts the value of 11237 into memory f o r the
current limit calibration constant.
P9 - Put User Defined Message
T h e P9 command stores user defined messages in the internal calibration memory.
T h e message may be read with a G9 command. T h e message may consist of
u p to 16 ASCII characters a n d typically represents the instruments identil'ication,
calibration date, etc. Lower case letters a r e converted to upper case. T h e
d a t a must be entered i n alphanumeric f o r m a t a n d must be s u r r o u n d e d by single
quotes (ASCII 39).
Example
"'CALDATE 7.13.87'p9"
PI0
-
Explanntiorz
Loads t h e message "CALDATE 7.13.87" into the
non-volatile memory.
Put S R Q Mask
T h e P10 command programs the LDT-5910/1227 to make service requests on
user-specified conditions. T h e two digit number code f o r the S R Q mask is
interpreted below.
00
01
02
04
08
16
32
T o disable the SRQ
F o r S R Q on a n A / D Overrange
For S R Q on a n Unsuccessful Temperature Calculation
F o r S R Q on a C u r r e n t Limit Condition
F o r S R Q on a Voltage Limit Condition
F o r S R Q on a Thermal Limit Condition
F o r S R Q on a Software Error
T o enable more t h a n one condition, a d d the numbers to get the mask value.
Numeric entries f o r the P10 command must be between 0 a n d +63 inclusive or
a n e r r o r will occur a n d the S R Q mask will not change. T h e e n t r y may be
expressed a s a n integer, real number as described in t h e n command. a n y
factional p a r t is ignored. For more information on the S R Q mask r e f e r to
sections 3.18 a n d 3.19.
Example
Explanatio~z
Sets the S R Q mask t o 17 a n d enables a S R Q
on A / D Overrange o r T h e r m a l Limit.
Sets the S R Q mask to 01 a n d enables t h e S R Q
o n A I D overrange.
T h e controller is alerted to generate a S R Q
when there is a Software E r r o r or a voltage
limit condition. All other errors still e f f e c t
the error status register, a n d c a n be r e a d with
the GO command, but d o not generate a Service
Request.
3.15 Terminator Commands
T h e terminator commands select what terminators the LDT-591011227 appends to
every output string. T h e available terminators a r e Carriage R e t u r n , Line fced
a n d End or Identify. C R a n d L F a r e ASCII control codes, sent over the d a t a
lines just like o u t p u t data. EOI is a uni-line message which is sent simultaneously with the last character in the output string. Normally ,each o u t p u t string
is terminated w i t h C R followed by L F a n d EOI. T h e LDT-591011227 defaults to
WO on power u p a n d a n y device clear command.
Example
Explanatiorz
T h e host computer will append a carriage rcturn
a n d a line feed to each command that is sent.
3.16 Clear Command
T h e asterisk command resets the LDT-5910/1227 to the power-up d e f a u l t settings
a n d clears all registers a n d buffers except f o r the i n p u t b u f f e r . T h e remote/local status remains unchanged. T h e asterisk is executed in its proper t u r n in a
string, just like a n y other command, without a f f e c t i n g the contents of the i n p u t
buffer. All commands which precede the * command a r e performed. T h e asterisk
is useful to insure t h a t the LDT-5910/1227 is initialize to the same state each
time a program is r u n . By contrast the similar interface messages DCL (Device
Clear) a n d SDC (Selected Device Clear) cause the entire i n p u t b u f f e r to be cleared
immediately.
Example
Explanat iotz
These commands f i r s t resct the LDT-5910/1227
to the power-up configuration of a u t o display
mode, output off a n d local mode. T h e t20
command places the u n i t in remote a n d sets
the control temperature to 20.0 C a n d the output
is t u r n e d on.
3.17 Self Test Command
T h e ZO command starts the diagnostic self-tests. If a n error is detected a n error
message is loaded into the output b u f f e r a n d displayed on the f r o n t panel After
the last test, the LDT-5910/1227 is reset to the power-on condition a n d the display
indicates actual temperature.
Since the LDT-5910/1227 is reset a t the end of the self-test the ZO command
should only be sent by itself. T h e LDT-5910/1227 will ignore a n y subsequent
commands in a command string.
Example
"z0"
T h e LDT-5910 does a diagnostic self test a n d
resets to the Power On conditions.
T h e LDT-591011227 diagnostic self test is pcrformed. T h e instrument then dcfauits to t h e
power-up settings a n d the L1 command is ignored.
3.18 Control Mode Command
YO Enable Local Mode
This command will return the LDT-5910/1227 to local mode a f t e r the Local
Lockout command is issued.
Y1 Enable Remote Mode
This command is automatically sent f r o m the 1227 interface board to the LDT5910 with a n y device dependant command. It is primarily reserved f o r remote
operation via a n RS-232 interface connection.
Y 2 Enable Local Lockout Mode
Local Lockout Mode will disable the remote/local button on the f r o n t panel of
the LDT-5910. T h e instrument cannot be returned to local mode until the
Enable Local Mode command (YO) is sent.
Example
Explartatio/z
T h e instrument is placed in local lockout a n d the
f r o n t panel controls a r e disabled (including the
LOCAL /REMOTE switch). T h e Auto display
mode is activated.
T h e LDT-5910/1227 is returned to local mode.
3.19 Service Requests
Service requests let bus instruments get the attention of the host computcr. If
more t h a n one instrument on the bus is capable of sending service requests, thc
host c a n l e a r n w h i c h one made the request by t a k i n g a serial poll. Each device,
including the LDT-5910, responds to the poll by sending the contents of its scrial
poll register. T h e serial poll register indicates whether the device requested
service, a n d if so, t h e reason f o r the request. Service requests a r e sent over a
separate line (one of the IEEE-488 bus lines called the SRQ line) a n d d o not
a f f e c t the o u t p u t b u f f e r .
T h e LDT-5910/1227 can be programmed to make a service request on user-specified
conditions. T h e conditions a r e specified by entering a value f o r t h e service request (SRQ mask) w i t h the P10 command (which c a n be read with the G10 command). T h e S R Q mask is a two digit integer t h a t specifies which conditions will
generate a service request. T h e SRQ mask works by selectively ignoring a n y
unspecified conditions of all the conditions t h a t a r e monitored by the serial poll
register in t h e LDT-5910.
3.20 The S e r i a l Poll Register a n d t h e S R Q hlask
T h e serial poll register is a binary register which contains eight bits, as shown
in table 3.4. T h e S R Q mask c a n enable a n y combination of serial poll register
bits 1 through 6. Its six-bit binary representation is AND-ed bit-for-bit w i t h
error register bits 1 through 6 a n d the results sent to the serial poll register. If
a n y mask-enabled bit in the serial poll register comes t r u e t h e R Q S bit (bit 7) is
set true, generating a service request.
At power-up of on a n y device-clear command, the S R Q mask is set to 00. T h i s
prevents service requests by holding each bit false under all conditions. T h e
serial poll register is cleared whenever the LDT-5910/1227 receives a new i n p u t
command string.
Table 3.4 Serial Poll Register
Bit
Condition
No E r r o r
A / D Overrange
Temperature Calculation Unsuccessful
C u r r e n t Limit
Voltage Limit
T h e r m a l Limit
Software Error
RQS
3.21 Interface Messages
Programmers working w i t h high level languages (like BASIC) generally need n o t
be concerned w i t h these messages since they a r e o f t e n handled by the internal
software drivers. T h e interface messages understood by t h e LDT-59 10/1227 a r e
listed in Table 3.5. All of these messages originate a t the controller.
Table 3.5 Interface Messages
-
Addresses the 1227 to listen.
MLA
My Listen Address
MTA
My T a l k Address - Addresses the 1227 to talk.
UNL
Unlisten - Addresses all devices to unlisten.
UNT
Untalk
ATN
Attention - A uni-line message t h a t instructs t h e 1227 to interpret
a multi-line message as a n i n t e r f a c e message (as opposed t o a device
dependent command).
DCL
Device Clear - A multi-line message t h a t causes the 1227 to reset to
its power-up configuration: o u t p u t o f f , a u t o display a n d local mode.
LLO
Local Lockout - A multi-line message t h a t disables a l l LDT-5910/1227
front-panel controls including the LOCAL/REMOTE button.
GTL
G o T o Local
SDC
Selected Device Clear - Causes the 1227 to reset t o its power u p
configuration: output o f f , mode set to local. This command d i f f e r s
f r o m D C L above in t h a t it a f f e c t s only t h e addressed i n t e r f a c e wherea s DCL a f f e c t s all listeners on the bus.
REN
Remote Enable - A uni-line message which, when received w i t h MLA,
switches t h e LDT-5910/1227 t o remote. When R E N is set false the
LDT-5910/1227 switches to local a n d removes t h e local lockout.
-
Addresses all talkers to untalk.
-
Causes the LDT-5910/1227 to switch t o L O C A L mode.
3.22 Example Programs
An example program is shown below that exercises commonly used, rcrnotely accessible features of the LDT-5910/1227.
10 .............................
T C T R L l ..............................
12 '
14 'Program to control the LDT-5910 to a user specified temperature
16 'and determine when temperature stabilization has been achieved.
20 '
24 'This program is written for use with a n IBM P C / X T or compatible
26 'using IOTech's GP488 controller card a n d PERSONAL488 software
28 '(IOTech, PO Box 21204, Cleveland, OH 44 121).
30 '
32 'The program is written i n Microsoft's GWBASIC a n d will also r u n
34 'under IBM's BASICA.
90 ...................................................................
100 '
102 ' Set u p program parameters
104 '
110 ADDR$="O 1"
'LDT-59 10 GPIB bus address
120 '
122 DELTMAX = .5
'Acceptable temp tolerance in deg C
124 DTDSMAX = .1
'Acceptable temp change rate in deg/sec
180 '
182 K E Y O F F
200 '
202 ' Initialize the GPIB device software drivers
204 '
210 OPEN "\DEV\IEEEOUTMFOR O U T P U T AS #1
212 OPEN "\DEV\IEEEINWFOR INPUT AS #2
300 '
302 ' Initialize the LDT-5910
304 '
3 12 P R I N T # 1, "OUTPUT ";ADDR$;";GO"
'Check error status
3 14 P R I N T # 1,"ENTER ";ADDR$
316 I N P U T #2, R $
318 I F V A L ( R $ ) o O T H E N BEEP : LOCATE 12,l : P R I N T "ERROR DETECTED: ";R$
: END
340 '
342 PRINT #l,"OUTPUT ";ADDR$;";W1"
'Set output terminator to < C R > <LF>
400 '
402 ' Get user set temperature
404 '
406 SLAST=O
410 CLS : P R I N T "
TEMPERATURE CONTROLLER DRIVER"
.............................
412
PRINT "
420 '
422 LOCATE 10,l : I N P U T "SET TEMPERATURE (C)... ",TS$
500 '
502 ' Print output headings
-----------------------------~I
504 '
5 12 LOCATE 10'41 : PRINT "ACTUAL TEMPERATURE (C)... ";
514 LOCATE 11'41 : PRINT "RATE OF CHANGE (DEG/SEC)... ";
600 '
602 ' Send set temperature to the 5910, t u r n the output on a n d
604 ' the display mode to actual temperature
606 '
618 P R I N T #1, " O U T P U T ";ADDR$;"; TM;TS$;"0 1 D2"
620 '
621 ' Check to see if done
622 '
624 P R I N T #1, "ENTER ";ADDR$
'Get a temperature reading
626 I N P U T #2, R$ : SNOW=TIMER
630 '
634 TACT=VAL(R$) : TSET=VAL(TS$)
'Some calculations
636 DTDS=(TACT-TLAST)/(SNOW-SLAST)
640 '
642 LOCATE 10'68 : P R I N T R$;"
";
'Print c u r r e n t values
644 I F SLAST>O T H E N LOCATE 11,67 : P R I N T USING "##.##";DTDS;
650 '
652 SLAST=SNOW : TLAST=TACT
654 I F ABS(TACT-TSET)<DELTMAX A N D ABS(DTDS)<DTDSMAX T H E N 700
660 '
661 ' Wait f o r 2 sec delay before getting new reading
662 '
664 I F TIMER-SNOW<2 T H E N 664 ELSE 622
700 '
701 ' Program termination
702 '
7 12 BEEP
7 14 LOCATE 15,20 : P R I N T "DONE...S T R I K E <CR> T O REPEAT"
720 '
722 A$=INKEY$ : I F A$="" T H E N 722
724 I F A$=CHR$(13) T H E N 400
730 '
732 CLS
734 END
CHAPTER 4
THEORY O F OPERATION
4.1
Introduction
There a r e three electronic circuit boards inside the LDT-5910. T h e y a r e the
Power Supply Board, the Main Board which contains the microprocessor a n d the
analog circuitry, a n d the Display Board which contains the f r o n t panel display
a n d the display circuitry. A f o u r t h board, the optional model 1227 GPIB/IEEE488 interface, may be installed. A functional block diagram of the LDT-5910 is
shown in F i g u r e 4-1. You may also want to refer to the schematics in Appendix
C. This chapter explains each board a n d each circuit i n the block diagram.
4.2
Power Supply Board
4.3
Internal Power Supplies
T h e internal power supplies include a +15 a n d -15 VDC supply f o r the main
board, a n unregulated 12 volt supply f o r the main current source a n d two +5 volt
DC regulated supplies. O n e +5 volt supply powers the internal analog a n d digital
circuitry a n d the other is reserved f o r the 1227 GPIB/IEEE-488 interface board
when it is installed. T h e GPIB/IEEE-488 supply is isolated, through the transformer a n d w i t h a separate ground, f r o m the other power supplies.
Power is supplied through the rear panel mounted e n t r y module 2401 which provides in-line transient protection a n d R F filtering. T h e back panel also houses
the i n line fuse F401. T h e main power switch SlOl is locatcd on the m a i n circuit board a n d supplies power to the transformers T201 a n d T202. T w o jumpers
located on the power supply subassembly select series or parnllel connection of
the transformer primaries f o r operation f r o m 115 VAC or 230 VAC respectively.
T h e +15 a n d -1 5 volt supplies use a full-wave, center-tapped bridge rectifier a r r angement (BR201) followed by voltage regulators (U201, U202). Capacitors installed before a n d a f t e r the regulators provide filtering. Each +5 volt supply has
a full-wave bridge rectifier (BR202, BR204) followed by a three-terminal regulator
(U203, U204) a n d appropriate filtering capacitors.
T h e unregulated bipolar current supply uses a full-wave, center-tapped bridge
rectifier (BR203) followed by filter capacitors. This power is supplied unregulated to the main board.
4.4 Main Board
4.5
Constant Current Source
T h e constant c u r r e n t source is formed by U l O l a n d its associated circuitry a n d
supplies either 10 u A or 100 uA to t h e externally connected thermistor. As the
current flows through the external thermistor, a voltage proportional to resistance
develops across the thermistor terminals. This voltage is b u f f e r e d by U102. T h c
back panel c u r r e n t switch selects the output current a n d the position of this
switch is also sensed by the microprocessor so t h a t it correctly calculates resistance a n d temperature.
4.6
Input Buffer
A unity gain b u f f e r (U102) presents a high impedance i n p u t to t h e thermistor
a n d provides a d e q u a t e output d r i v e capability f o r succeeding stages. T h e voltage
output of this b u f f e r is proportional to the sensed resistance of t h e thermistor
a n d represents t h e actual thermistor temperature. T h i s signal is applied t o the
d i f f e r e n c e amplifier (U103C) a n d is also sent through the analog switch (U109) to
the A / D convertor (U108) where i t is read by the microprocessor a n d used to
compute actual temperature.
4.7
Difference Amplifier
T h e d i f f e r e n c e amplifier (U103C) compares the actual temperature signal, f r o m
the i n p u t b u f f e r , to the set point temperature signal. T h e set point temperature
signal comes f r o m t h e main control knob, when in Set Temperature or A u t o mode,
or f r o m the set point control D / A (U107B) when in remote o r lock mode. T h e d i f ference signal a t the output of U103C is available to the gain stage a n d t h e integrator input.
4.8
Digitally Controlled Gain Stage
T h e digitally controlled gain stage consists of a feedback amplifier (U103A), the
analog switches U l l O a n d feedback resistors. T h e analog switches v a r y t h e ratio
of resistance i n the feedback circuit to change the gain to 1, 3, 10, 30, 100 or
300. T h e gain setting determines how f a s t the LDT-5910 reaches t h e set point
temperature a n d how quickly i t settles t o this temperature.
4.9
Integrator
T h e signal f r o m the d i f f e r e n c e amplifier is sent to a n integrator (U103B) which
reduces the d i f f e r e n c e between t h e set point temperature a n d the a c t u a l temperat u r e t o zero, regardless of the gain setting. A n analog switch (U110) discharges
the integrating capacitor a t power-up a n d when the o u t p u t is t u r n e d o f f to prevent
unnecessary d i f f e r e n c e signal integration.
4.10 Summing Amplifier
T h e summing amplifier (U103D) sums the signal f r o m the integrator with the
signal f r o m t h e digital controlled gain a n d sends this signal to t h e voltage controlled c u r r e n t source.
4.11 Current Limiting
The o u t p u t of the summing amplifier (U103D) acts as the control signal to the
main voltage controlled current source. O u t p u t c u r r e n t limiting is e f f e c t e d by
bounding the control signal so that i t is always less t h a n the limit current. T h e
limit c u r r e n t is set with the f r o n t panel controls or through the GPIB i n t e r f a c e
bus. T h e bipolar c u r r e n t limit levels a r e established by the o u t p u t of the current
limit D / A a n d the unity gain invertor U104B. U104A, U104C, 4 1 0 4 a n d the associated circuitry provide the necessary control signal bounding.
4.12 Current Limit D/A
T h e current limit D / A converter is made u p of U107A a n d U105B. T h e microprocessor loads the digitally stored current limit value into t h e 12 bit D / A (U107A)
which converts i t t o a voltage a t the output of UlO5B. T h e c u r r e n t limit value
is updated a t power-up a n d whenever the value is changed.
4.13 Current Limit Condition Sensing
Comparators U112C a n d U112D sense the output of U104A to determine when
o u t p u t c u r r e n t limiting is occurring. When this condition occurs, 1 / 0 port A0 of
U127 is pulled low by the comparator to signals the microprocessor. T h e microprocessor responds by flashing the f r o n t panel LIMIT L E D a t approximately 2 Hz
a n d then updates its internal error status register.
4.14 Voltage Controlled Current Source
T h e bounded o u t p u t control signal is applied t o U104D. This a m p l i f i e r along with
darlington transistors Q102, 4 1 0 3 , a n d the c u r r e n t sensing amplifier U113 f o r m the
output voltage controlled current source. T h e o u t p u t of this stage directly drives
the externally connected T E cooler module. A one-tenth volt signal a t t h e i n p u t
to this stage causes a one a m p output.
4.15 Voltage Limit Condition Sensing
Comparators U112A a n d U112B sense t h e o u t p u t of U104D to determine when output compliance voltage limiting is occurring. T h i s condition occurs whenever the
LDT-5910 rear panel T E cooler output is open or connected to a high resistance.
If this condition occurs, one of the comparators pulls 1 / 0 port A1 of U127 low,
signaling t h e microprocessor. T h e microprocessor responds by flashing t h e f r o n t
panel LIMIT L E D a t approximately 4 Hz a n d updates its internal e r r o r status
register.
4.16 S e t P o i n t Control D/A
When t h e LDT-5910 goes into the LOCK mode the position of t h e control knob is
converted to a digital number a n d stored. T h i s digital number is reconverted to
a n analog signal a t the D/A convertor (U107B) a n d then f e d through the c u r r e n t
to voltage o p a m p (U105C). When the LDT-5910 is in LOCK mode or R E M O T E
mode the o u t p u t of U105C establishes t h e set temperature control signal a t the
i n p u t to U103C.
4.17 Precision Voltage Reference
T h e precision voltage reference (U105A) provides reference voltages f o r the m a i n
control knob (RV501), the A / D convertor (U108), a n d the D/A converters (U107).
U105D b u f f e r s the output of the resistor divider network f o r driving the 10K
ohm load presented by RV501.
4.18 A / D Convertor
T h e A / D converter (U108) is a monolithic, 12 bit converter with a 35 msec conversion time. This converter, along with a CMOS analog switch (U109), allows
the microprocessor to read analog signals i n the LDT-5910. In particular, the
actual temperature, set temperature, and position of the f r o n t panel control knob
(RV501) is read.
4.19 Microprocessor
T h e LDT-5910 uses a CMOS 8085 microprocessor (U120) to control its internal
operations. T h e address decoder (U128) selects the memory, either the R A M
(U124), R O M (U122) or EEPROM (U l23), the 8085 c a n access. T h e 1 / 0 decoder
(U126) selects the 1 / 0 device the 8085 can access. T h e available 1 / 0 devices on
the main board a r e the serial interface (U125), the main board 1 / 0 port (U127),
the current limit D / A (U107A), the set point control D / A (U107B), a n d the A / D
converter (U108).
T h e counters (U130 a n d U131) interrupt the microprocessor to update the display
a n d provide a f a i l safe countdown which generates a reset i n the event of a
malfunction.
Since the lower eight address lines i n the 8085 architecture a r e also used a s data
lines, a n address latch (U121) holds necessary address information w h e n d a t a is
loaded onto the bus. This latch is enabled by the ALE signal f r o m the 8085.
4.20 Memory
T h e LDT-5910 uses three types of memory. T h e f i r s t is short term memory, R A M
(U124), that is retained only while power is applied to the unit. T h e second is
256 K of read only memory, ROM (U122) which contains the internal instructions
that make the LDT-5910 function as a temperature controller. T h e t h i r d type of
memory is electrically erasable programable memory, EEPROM (U123). EEPROM
stores calibration constants a n d other d a t a which must be retained even when
power is removed f r o m the unit. Examples of d a t a stored in this memory include
the GAIN, LIMIT, C1, C2, C3, a n d calibration constants. EEPROM may be reprogrammed a t least 10,000 times, providing ample capacity f o r most applications.
4.21 Serial Interface
T h e 8085, i n the LDT-5910, communicates with external controllers through a serial
interface. Parallel d a t a f r o m the microprocessor is converted to a bi-directional
serial signal a t the asynchronous serial interface (U125).
4.22 Latched Parallel I/O Port
T h e latched parallel 1/0 port (U302) is a n 8255 1 / 0 controller t h a t controls all
of the analog switches on the main board a n d acts as a n input port for several
digital input signals (current limit, voltage limit, thermal limit, etc).
4.23 Display Board
4.24 Display Driver
T h e display d r i v e r (U301) is a specialized output port that requires f o u r 1 / 0 a d dresses. Each address corresponds one of the f o u r f r o n t panel display digits.
Internal bus d a t a is written to these addresses, decoded a n d appears on the LDT5910 f r o n t panel display.
4.25 Latched Parallel 1 / 0 Port
The latched 1 / 0 port (U302) is used to sample the f r o n t panel input switches a n d
drive all of t h e f r o n t panel LEDs.
4.26 LED Drivers
U303, U304, a n d U305 provide the output current sinking capability necessary to
drive the f r o n t panel LEDs.
4.27 GPIB Interface Board
4.28 Microprocessor and Memory
T h e 1227 IEEE-488/GPIB interface, shown in figure 4-2, uses the 8085 microprocessor (U101) to control its operations. T h e interface card has PROM a n d R A M memory
( U 104).
T h e interrupt timers (U113 a n d U114) interrupt the microprocessor to provide a
f a i l safe countdown counter that generates a reset if there is a malfunction.
Since the lower eight address lines in the 8085 architecture a r e also used as data
lines, a n address latch (U102) holds necessary address information when d a t a is
loaded onto t h e bus. This latch is enabled by the ALE signal f r o m the 8085.
4.29 Optical Isolators
The optical isolators (U106 a n d U107) isolate the LDT-5910 f r o m the GPIB interface bus.
4.30 Serial Interface
T h e parallel signal is converted to a serial signal a t the synchronous
face (U105). T h e serial input a n d output lines a r e optically isolated
main board. T h e serial interface is bi-directional. It receives scrial
f r o m the interface controller a n d converts it to a parallel signal f o r
processor.
serial interf r o m the
information
the micro-
4.31 GPIB Interface
T h e microprocessor communicates w i t h t h e IEEE S t a n d a r d 488 i n s t r u m e n t a t i o n b u s
t h r o u g h t h e 8291 G P I B T A L K E R / L I S T E N E R c h i p U110. T h i s c h i p implements a11
of the IEEE 488 Standards' i n t e r f a c e functions, except f o r controller operations.
T h e o u t p u t of t h e i n t e r f a c e controller is sent to bus l i n e d r i v e r s U111 a n d U112.
OPTO-ISOLATORS
+
1
SERIAL INTERFACE
MEMORY
CONTROLLER
RAM, RUM
8085
MICROPROCESSOR
GPIB B U S
CONTROLLER
,
i
GPIB BUS
FIGURE 4 - 2 FUNCTIONAL BLOCK DIAGRAM OF 1227 INTERFACE
CHAPTER 5
MAINTENANCE
5.1
Overview
This chapter describes how to maintain the LDT-5910. Included a r e sections
covering calibration, fuse replacement, line voltage selection, a n d disassembly.
WARNING
T H E SERVICE PROCEDURES DESCRIBED IN T H I S CHAPTER
ARE FOR U S E BY QUALIFIED PERSONNEL. POTENTIALLY
LETHAL VOLTAGES EXIST WITHIN T H E LDT-5910. T O AVOID
ELECTRIC SHOCK, DO NOT PERFORM ANY O F T H E PROCEDU R E S DESCRIBED IN T H I S CHAPTER UNLESS Y O U ARE QUALIFIED T O DO SO.
5.2
Calibration
T h e LDT-5910 should be calibrated every 12 months or whenever performance
verification indicates t h a t calibration is necessary.
5.3 Recommended Equipment
Recommended test equipment f o r calibrating the LDT-5910 is listed i n Table 5.1.
Equipment other t h a n t h a t shown in the table may be used i f the specifications
meet or exceed those listed. If your LDT-5910 is equipped \i-ith the model 1227
GPIB/IEEE-488 interface r e f e r to sections 5.9 a n d 5.10 f o r calibration procedures
using the GPIB bus.
Table 5.1 Recommended Test Equipment
Descrivtion
DMM
Resistor
5.4
Mf n./Model
Fluke 8840A
Metal Film
Specification
DC Amps (@ 1.0 A): + I O/o
Resistance (@I 10 ohms):.02
O/o
9.00 to 9.9K f o r 100 uA calibration
90.0 to 99.9K f o r 10 uA calibration
10.00 K f o r current limit calibration
Environmental Conditions
Calibrate this instrument under laboratory conditions. We recommend calibration
a t 23 " C f 1.0 "C. When necessary, however, the LDT-5910 may be calibrated a t
its intended use temperature if this is within the specified operating temperature
range of 0 to 50 " C.
5.5
Warm-up
T h e LDT-5910 should be allowed to warm u p f o r a t least 1 hour before calibration.
5.6 Calibration Adjustments
There a r e only three calibration adjustments that need to be made f o r this unit.
They a r e to calibrate the resistance a t the 10 microamp a n d the 100 microamp
source c u r r e n t settings a n d to calibrate the current limit. If you have the optional
Model 1227 IEEE-488/GPIB interface you may follow the procedure in sections
5.9 a n d 5.10 to calibrate the LDT-5910 f r o m the bus. All calibrations can be
done with the case closed. T h e instrument is calibrated by changing the i n t e r n a l l y
stored digital calibration constants.
5.7
Manual Resistance Calibration
a.
Set the back panel switch to the 10 u A position.
b.
Measure a n d record the exact resistance of your metal f i l m resistors.
c.
Connect the correct metal f i l m resistor to the thermistor i n p u t of the LDT59 10.
d.
Enter the resistance calibration mode by pushing local a n d select a t the
same time. T h e LED display will now indicate resistance in K ohm.
e.
T u r n the main control knob until the display indicates the same resistance
you recorded f o r the metal f i l m resistor.
f.
Press the set button to store the new value into non-volatile memory.
g.
Switch the back panel switch to the 100 uA position a n d repeat this
procedure with the other resistor.
5.8
Manual Current Limit Calibration
a.
With t h e output o f f , connect a calibrated ammeter to the T E module
output of the LDT-5910.
b.
Set the current limit to 1000 mA (1 amp).
c.
With the output o f f , turn the knob to mid-scale (about f i v e turns clockwise).
d.
T u r n t h e output on.
e.
Record the current indicated on the calibrated ammeter.
f.
T u r n the o u t p u t o f f .
g.
Press t h e LOCAL a n d O U T P U T ON button a t the same time to place the
LDT-5910 in the Current Calibration mode.
h.
If the number on the LED display is d i f f e r e n t f r o m the number t h a t the
calibrated ammeter indicated, t u r n the main control knob until i t reads
the number that you recorded.
Press the set button to store the new calibration value into non-volatile
i.
memory.
Input a new c u r r e n t limit value since the current limit must bc resct t o
use t h e new calibration value.
j.
5.9
Resistance Calibration Over the G P I B Bus
Set t h e back panel switch to the 10 u A position. T h e bus commands f o r
calibrating the 10 uA a n d 100 uA a r e given here with the commands f o r
the Cal RlOO given in parenthesis.
Measure a n d record the exact resistance of your metal f i l m resistors.
Connect the correct metal f i l m resistor to the LDT-5910 thermistor input.
Set t h e display to read actual resistance by sending the bus command
"D5".
Record the indicated resistance f r o m the LDT-5910 f r o n t panel display.
Send t h e "G6" (G7) bus command to read the Cal R10 value. Record this
number.
Calculate t h e new value f o r Cal R10 using the following equation:
New Cal R = Measured Resistance
Displayed Resistance
*
Old Cal R
I n p u t a new Cal R10 value with the "P6" (P7) command.
Switch the back panel switch to the 100 u A position a n d repeat this
procedure w i t h the other resistor a n d the bus commands i n parenthesis.
5.10 Current Limit Calibration Over the GPIB Bus
a.
With t h e o u t p u t o f f , connect a calibrated ammeter to the T E module o u t p u t
of the LDT-5910.
b.
Set t h e c u r r e n t limit to 1000 mA (1 amp) with the bus command "N1000Pl".
c.
Connect a 10K thermistor to the thermistor terminals.
d.
I n p u t a set temperature of 5 0 ° C with the GPIB command "T50."
e. T u r n the output on with the bus command "01."
f.
Record the current indicated on the calibrated ammeter.
g.
Retrieve the Cal CL value with the "G8" command.
h.
Turn the output off.
i.
Calculate the new Cal CL value using the equation:
New Cal CL = Actual Current
Set Current
j.
* Old
Cal CL
Input a new current limit value since the current limit must be reset to
use the new calibration value.
5.11 Fuse Replacement
T h e fuse is accessible f r o m the rear panel of the LDT-5910. Before replacing
the fuse, t u r n power off a n d disconnect the line cord. Use only the fuses indicated below i n Table 5.2.
Table 5.2 Fuse Replacement
Line voltage
Fuse Reolacement
105
-
125 VAC
1 Amp, 3AG, Slow Blow
210
-
250 VAC
1/2 Amp, 3AG, Slow Blow
5.12 Line Voltage Selection
Line voltage selection is made by installing jumpers according to f i g u r e 5-1. Normally these jumpers a r e factory preset. When necessary, however, they may be
moved to accommodate new line voltage conditions. You must remove the LDT5910 top cover a n d then remove the power supply. T o remove the power supply,
remove the f o u r outside screws, closest to the side rails, a n d l i f t the power supply
straight up. Locate the zero-ohm jumpers on the Power Supply Board. Carefully
remove the jumpers a n d then install them in the new position.
5.13 Disassembly
T h e top a n d bottom covers of the LDT-5910 may be removed by extracting the
countersunk screws on the sides of the instrument near the rear panel. A f t e r
these screws a r e out, slide either cover towards the rear of the instrument a n d
then pull it u p a n d off.
To remove the f r o n t panel of the instrument f i r s t peel out the decorative plastic
inserts located on the sides of the f r o n t bezel to access the f o u r f r o n t panel
retaining screws. When the f o u r retaining screws a r e removed press on the back
of the f r o n t panel to press o u t the circuit board (the top cover must be removed
to allow access to this circuit board).
FIGURE 5-1 AC VOLTAGE SELECTION
CHAPTER 6
OPTIONAL MODEL 1227 GPIBIIEEE-488 INTERFACE
SPECIFICATIONS AND INSTALLATION
6.1
Overview
This chapter describes the optional model 1227 GPIB/IEEE-488 interface which 31lows the LDT-5910 to be remotely programmed via the IEEE standard 488-1978 interface bus. For a description of how to program remotely refer to Chapter 3.
With the optional 1227 GPIB/IEEE-488 interface installed, the LDT-5910 may be
controlled by most computers via the GPIB/IEEE-488 bus. When the 1227 interface receives a n y of its recognized commands f r o m the GPIB bus it sends appropriate control information to the LDT-5910 main board microprocessor via a n
optically isolated serial interface. Ground, receive a n d transmit lines a r e optically
isolated. In the case of interface messages such as DCL (device clear), G T L (go
to local), a n d R E N (remote enable), special ASCII characters a r e transmitted to
the LDT-5910. For example, when the 1227 receives the bus command R E N , it
responds by sending the character string " Y l " to the LDT-5910 main board. This
character string is then interpreted by the LDT-5910 as a remote enable command.
Upon receipt of these characters, the LDT-5910 responds appropriately.
T h e 1227 interface receives device dependent commands, such as DO (blank the
display), G9 (get user defined message), or T20.0 (control to 30.0 C), as ASCII strings a n d a r e simply passed to the LDT-5910 f o r interpretation a n d action. When
the 1227 interface is instructed to talk it signals the LDT-5910 t h a t d a t a is required. T h e LDT-5910 then transmits the appropriate d a t a back to the 1227 as
a serial stream of ASCII characters. T h e 1227 then loads these characters onto
the GPIB bus to complete the talk cycle.
6.2
Specifications
IEEE-488 BUS IMPLEMENTATION
General:
Implements talker/listener functions.
Interface Messages:
R E N , DCL, LLO, GTL, SDC
Isolation:
Instrument is optically isolated f r o m IEEE-488
bus.
Command Execution Time:
Approximately 40 msec.
POWER REQUIREMENTS
Isolated Supply:
+5 volts, 500 mA max.
Instrument Supply:
+5 volts, 100 mA max.
6.3 Installation
Install the GPIB interface (model 1227) using the following procedure:
Note: T h e 1227 GPIBIIEEE-488 interface board contains static sensitive parts. Handle the circuit board only by its edges a n d work
a t a static f r e e work station.
a.
T u r n o f f the LDT-5910 a n d disconnect it f r o m the AC line.
b.
Remove the top cover of the 5910 by removing the two cover retaining
screws located on either side of the instrument near t h e rear panel.
c.
Remove the 5910 rear panel by unscrewing the f o u r screws located in the
corners of the panel.
d.
Remove the a l u m i n u m cover plate f r o m the rear panel of t h e 5910 to expose t h e cutouts f o r the GPIB connector a n d address selector switch.
e.
Fasten the 1227 interface board onto the rear panel w i t h t h e supplied
GPIB connector retaining screws, lock washers a n d nuts. Center t h e GPIB
connector a n d address selector switch in their respective panel cutout
holes. Note t h a t the 1227 interface board must be mounted upside down
(components facing down) to be correctly installed.
f.
Insert the supplied plastic fasteners into the each upper channel of the
5910's side rail to support the f r o n t of the GPIB bonrd. Slide t h e support
to a position approximately 4 3/8 inches f r o m the bnck panel. (See Figure
6.1).
h.
Screw t h e right angle brackets into the plastic side rail fasteners.
Note: O n e f a c e of the bracket has a threaded hole f o r t h e screws t h a t hold the GPIB board to the brackets. Do not screw
t h e threaded f a c e of the bracket into the plastic fasteners.
Tighten the screw into the plastic side rail fastener to lock the support
i n t o place.
i.
Install the ribbon cables f r o m pin header J105 on t h e main c i r c u i t board
to t h e GPIB board. When correctly installed t h e cables r u n i n towards
t h e center of the main circuit board (see Figure 6.1) without a n y twists.
j.
Replace the LDT-5910 rear panel a n d attached GPIB i n t e r f a c e board a n d
replace the f o u r retaining screws on t h e rear panel.
k.
Screw t h e f r o n t of the GPIB board to the mounting brackets w i t h the s u p
plied 6-32 mounting screws.
1.
Replace the top cover of the LDT-5910.
Appendix A
The Steinhart-Hart Equation
Two terminal thermistors have a non-linear relationship betwccn tcrnperature a n d
resistance. T h e resistance verses temperature characteristics f o r a family of
similar thermistors is shown in figure A-1. It has been f o u n d empirically
that the resistance verses temperature relationship f o r most common negative
temperature coefficient (NTC) thermistors can be accurately modeled by a
polynomial expansion relating the logarithm of resistance to inverse
temperature. T h e Steinhart-Hart equation is one such expression a n d is given
as follows:
1/T = A
+
B(Ln R )
+ C(Ln
R ) ~
Equation 1
Once the three constants A, B, a n d C a r e accurately determined, equation 1
introduces very small errors in the calculation of temperature even over
wide temperature ranges. Table A.l shows the results of using equation
1 to f i t the resistance verses temperature characteristic of a common 10K ohm
(at room temperature) thermistor. Equation 1 will produce temperature calculation
errors of less t h a n 0.01 C over the range -20 C to 50 C.
------- Error
T ( "C)-------
T
First Order
T h i r d Order
Actual
Fit. ~ q . 1 ~ Fit E q . 23
-------- --------- --------- -------97072
-20.00
-0.00
-0.32
55326
-10.00
0.00
-0.06
32650
0.00
-0.00
0.09
19899
10.00
-0.00
0.15
12492
20.00
-0.00
0.13
10000
25.00
0.00
0.08
8057
30.00
0.00
0.0 1
5326
40.00
0.00
-0.20
3602
50.00
-0.00
-0.50
R'
Table A.l Comparison of Curve Fitting Equations
Resistance of a 10K, Fenwal UUA41J1 thermistor.
constants A'=0.963
*
lov3, B'=2.598
Constants A=1.125 *lo-3 (C1=1.125)
Bz2.347 * 10-3 (C2=2.347)
C=0.855 *lo-7 (C3=0.855)
THERMISTOR R/T CURVES
FOR VARYING ROOM TEMP RESISTANCES
-60
-40
-20
0
20
40
60
80
100
120
140
160
TEMPERATURE (DEGREES CELCIUS)
FIGURE A - I THERMISTOR
RESISTANCEVFR
TEMPERATURE
In practice we h a v e f o u n d t h a t the constants A, B a n d C f o r virtually all
common thermistors lie within a narrow range. Consequently, we h a v e dcfined
the constants C1, C2, C3 as follows:
T h e constants C1, C2, A n d C3 may all be expressed in the f o r m n.nnn simplifying
entry into t h e LDT-5910.
If high accuracy is not required, the Steinhart-Hart equation may be simplified to
a f i r s t order polynomial:
1/T
=
A'
+ B' *
In R
Equation 2
This equation is easier to solve a n d often provides a d e q u a t e results. T a b l e
A.l also shows t h a t t h e use of equation 2 introduces temperature errors of less t h a n
0.5 " C over the range -20 C to 50 "C. Once t h e constants A' a n d B' a r e determined,
the LDT-5910 is programmed with the following values of C1, C2 a n d C3:
Table of Constants
We have tested or reviewed many thermistors a n d include the a p p r o p r i a t e calibration
constants f o r t h e temperature range -20 C to 50 C in most cases. Please contact
I L X Lightwave Corporation if you require more information a b o u t these constants
or would like o t h e r constants computed f o r you.
Table A.2 Thermistor Constants
Manufacturer a n d Tvue
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Fenwal
Curve
Dale
Curve
Curve
Dale
Curve
Dale
Dale
Curve
Dale
Curve
Dale
Curve
Dale
Curve
Curve
Dale
Dale
Curve
Dale
Curve
Dale
Curve
Dale
Curve
Dale
Curve
Curve
Dale 2 . 2 5 2 ~ 625C
Spectra Diode Labs Modules
Lasertron Modules
General Optronics Modules
1
1
1
10A
10A
10A
16
16
16
17
17
17
18
18
18
1
1
1
1
1
1
1
1
1
2
2
2
9
1
Computer program
We have also included two computer programs t h a t use a least squares c u r v e f i t t i n g
routine to determine t h e values of C1, C2 a n d C3. T h e programs, called STEIN3
a n d S T E I N I , a r e written in IBM's advanced BASICA. STEIN3 calculates the valucs
the coefficients C1, C2 a n d C3 using equation 1. STEIN1 calculates C1 a n d C2 using equation 2. T y p e one of these program into your computer.
Next you must create a d a t a f i l e f o r your thermistor t h a t describes the resistance
a t various temperatures. T h e temperature verses resistance calibration d a t a can
be obtained f r o m the thermistor manufacturer. Enter the resistance a t various temperatures as d a t a points into a n ASCII file. You can write t h e d a t a f i l e on a
word processor, b u t you must use non-document mode so special word processing
characters a r e not inserted into the d a t a file. Format the d a t a w i t h one tcmperature-resistance pair per line a n d a t least one space separating the two numbers.
Temperatures should be in centigrade a n d resistances in ohms. We recommend t h a t
you use a t least twenty d a t a points, uniformly spread over the intended range of
use, f o r a n accurate determination of the coefficients. Enter a -1 to signify the
end of the resistance d a t a a n d temperature data.
A small sample d a t a f i l e is included below as a n example of the d a t a f o r m a t and
end-of-data m a r k e r (R = -1).
Temperature
Resistance
R u n the S T E I N 3 or STEIN1 program. T h e best curve f i t t i n g values f o r C1, C2 and
C3 will be displayed. K e y these numbers into the LDT-5910. If t h e computer program supplies negative values f o r constants C2 or C3 then the t e m p e r a t u r e verses
resistance d a t a was bad or incorrectly entered.
80REM
*
**************
STEIN1
****************
90 REM
-
92 REM
94 R E M
100 REM
110 REM
120 REM
130 R E M
Rev: 3-1 1-87
Least squares f i t program to f i n d the thermistor cocf f icients
C1 a n d C2 in the following equation:
1 / T = C1
+
C2
* (ln R)
140 REM
-
-
.-
-
-
200 REM
210 R E M Variables:
220 R E M
230 R E M T[i], R[i]
temperature a n d resistance d a t a values.
240 R E M
250 REM Y[i] = l/T[i] the dependent variable (depends on R[i])
in the Steinhart - Hart equation (above).
260 R E M
270 REM
280 R E M X[i] = ln(R[I]) the value of the ith function of the independent
variable ln(R) (natural log of resistance)
290 R E M
330 REM
1000 DEFDBL A-Z
1010 DEFINT I, J, K, L
1020 DIM R[400], T[400], Y[400], X[400]
1025 C[3]=0
1030 PRINT "What is the data file name"; : INPUT D$
1040 OPEN "i", 1, D$
1050 R E M
**** read a n d echo T(i), R(i) f r o m the d a t a file ****
1060 R E M
(terminate read on R = - I )
1070 1=0
1080 PRINT "Data:"
1090 G$="Point
Temperature (Celsius) Resistance (ohms)"
1100 H$=" # # #
#####.##
########.##"
1 1 10 P R I N T G$
1120 P R I N T
1130 I=I+l
1 140 INPUT #1, T(I), R(1)
1150 IF R(I)<O T H E N G O T 0 1180
1 155 X(I)=LOG(R(I)) : Y(I)= l/(T(I)+273.15)
1160 P R I N T USING H$; I, T(I), R(1)
1170 G O T 0 1130
1180 N=I-1
1 190 CLOSE
1200 R E M
**** accumulate sums ****
1205 SX=O : SY=O : SXY=O : SXX=O
1210FOR I = 1 T O N
1220 SX=SX+X(I)
1230 SY=SY+Y(I)
1240 SXY=SXY+X(I)*Y(I)
1250 SXX=SXX+X(I)*X(I)
1260 N E X T I
1300 R E M
**** print out results ****
13 10 C[2]=(N*SXY-Sx*SY)/(N*SXX-SX*SX)
1320 C[1] = (SY-C[2ISSX)/N
1620 PRINT
C1
C2
C3"
1630 G$="Key in:
1640 P$="
#.###
#.###
#.###I8
1650 PRINT G$
1660 PRINT USING P$; C[l]* 1OOO!, C[2]* 10000!,C[3]
1700 '
1702 Cl=INT(C[l]* 1000000!)/ 1OOOOOO!
1704 C2=INT(C[2]* lE+O7)/ 1 E+O7
1706 C3=0
1710 PRINT
1712 PRINT "
T
T
T"
1714PRINT"
R
ACTUAL
CALC
ERROR"
1716 PRINT " --------------- --------- ---------- --------1718 P$= " # # # # # # #
####.##
###*.##
####.##"
1720 FOR L = l T O N
1730 X=LOG(R(L))
1740 TCALC=l /(Cl+C2*X+C3*X*X*X)-273.15
1760 PRINT USING P$;R(L),T(L),TCALC,T(L)-TCALC
1780 NEXT L
---------I!
90 R E M
92 R E M
94 R E M
100 REM
110 R E M
120 R E M
130 R E M
140 R E M
150 R E M
160 R E M
170 R E M
180 R E M
190 R E M
200 R E M
210 R E M
220 R E M
230 R E M
240 R E M
250 R E M
260 R E M
270 R E M
280 R E M
290 R E M
300 R E M
310 R E M
320 R E M
330 R E M
340 R E M
350 R E M
360 R E M
370 R E M
380 R E M
390 R E M
395 R E M
400 R E M
410 R E M
420 R E M
430 R E M
440 R E M
450 R E M
460 R E M
470 R E M
Rev: 3-1 1-87
Least squares f i t program to f i n d the thermistor coefficients
C1, C2 a n d C3 in the Steinhart-Hart equation:
1/T
=
C1
+ C2 *
(In R )
+
C3
* (ln
R)**3
Reference:
"Data Reduction a n d Error Analysis f o r the Physical Sciences"
Philip R. Bevington (McGraw-Hill, New York, 1969)
Library call no.: QA 278 B48
Variables:
T[i], R[i]
temperature a n d resistance d a t a values.
Y[i] = l/T[i] the dependent variable (depends on R[i])
i n the Steinhart - H a r t equation (above).
X[n,i]
the value of the n t h function of the independent
variable R (resistance) evaluated a t the ith
d a t a point R[i]
X[l,i] = 1 ; X[2,i] = ln(R[i]) ; X[3,i] = ln(R[i])
**
3
the value of the jth coefficient to be solved f o r
i n the expansion
c[j]
Y[i] = c[l]
*
X[l,i]
+ c[2] *
X[2,i]
+ c(3) *
X[3,i]
which becomes the Steinhart - H a r t equation
which is the inverse of the alpha matrix
with the above substitutions f o r Y[i] a n d X[n,i].
c[j] corresponds to Bevington's a[j] vector
in his eqn 8-26.
A[j,k]
Bevington's alpha matrix (j,k=1,2,3)
a n d beta vector (j=4, k=1,2,3) (Bevington eqn 8-23).
E[j,k]
Bevington's epsilon (error) matrix (eqns 8-28, 8-30)
a n d contains the uncertainties i n the estimates
480 R E M
of the c[j] coefficients. These uncertainties a r e
490 R E M
the consequence of the scatter (errors) i n the
500 R E M
input temperature verses resistance data.
510 R E M
1000 DEFDBL A-Z
1010 D E F I N T I, J, K, L
1020 DIM R[400], T[400], Y[400], X[4,400], A[4,3], B[3,3], E[3,3], C[3]
1030 PRINT "What is the data f i l e name"; : I N P U T D$
1040 OPEN "i", 1, D$
**** read a n d echo T(i), R(i) f r o m the data f i l e ****
1050 REM
(terminate read on R=-1)
1060 R E M
1070 1=0
1080 P R I N T "Data:"
1090 G$="Point
Temperature (Celsius) Resistance (ohms)"
#####.##
########.##"
1100 H$=" # # #
11 10 PRINT G$
1 120 PRINT
1130 I = I + l
1140 I N P U T # 1, T(I), R(1)
1150 I F R(I)<O T H E N G O T 0 1 180
1160 PRINT USING H$; I, T(I), R(1)
1170 G O T 0 1130
1180 N=I-1
1 190 CLOSE
**** calculate 4 x 3 matrix ****
1200 R E M
1210 F O R I = 1 T O N
1220 H=LOG(R(I))
1230 X(l,I)=l
1240 X(2,I)=H
1250 X(3,I)=H*H*H
(subscript 4 corresponds to y[i] = X[4,i])
1260 REM
1270 X(4,I)= l/(T(I)+273.15)
1280 N E X T I
1290 R E M **** Calculate alpha ( i = l to 3) a n d beta (i=4) ****
1300 R E M
(Bevington eqns 8-23)
1310 F O R 1=1 T O 4 : FOR J = l T O 3 : A(I,J)=O : N E X T J : N E X T I
1320 F O R 1=1 T O N : F O R J = l T O 4 : F O R K = l T O 3
1330 A(J,K)=A(J,K)+X(J,I)*X(K,I)
1340 N E X T K : N E X T J : N E X T I
1350 R E M **** Error matrix "E" = inverse of alpha (3x3 part of A) ****
1360 GOSUB 20 10
1370 R E M
**** Coefficients = beta (fourth column of A) x E ****
(eqn 8-26 of Bevington)
1380 REM
1390 F O R 1=1 T O 3 : C(I)=O : FOR J = l T O 3
1400 C(I)=C(I)+E(I,J)*A(4,J)
1410 N E X T J : N E X T I
1420 SIGMA=O
1430 FOR 1=1 T O N
1440 H=X(4,I)-C(l)*X(I ,I)-C(2)*X(2,I)-C(3)*X(3,1)
1450 SIGMA=SIGMA+H*H
1460 N E X T I
**** sigma = mean square deviation ****
1470 REM
1480 R E M
(Bevington eqn 8-29)
1490 SIGMA=SQR(SIGMA/(N-3))
**** print coefficients a n d estimated errors ****
1500 REM
1510 R E M
(eqns 8-26 and 8-30 of Bevington)
1520 F$="##.####^^^^ +/- ##.#+tAAAA)"
1530 PRINT
1540 PRINT "1/T = (";
-
-
1550 PRINT USING F$; C(l), SIGMASSQR(E(l,l))
1560 PRINT "
+ (";
1570 PRINT USING F$; C(2), SIGMA*SQR
1580 PRINT " * In (R)"
1590 PRINT "
+ (";
1600 PRINT USING F$; C(3), SIGMA*SQR
1610 PRINT " * In ( R ) ** 3"
1620 PRINT
C3"
C1
C2
1630 G$="Key in:
1640 P$="
#.###
#.###
#.###"
1650 PRINT G$
1660 PRINT USING P$; C[l]* 1OOO!, C[2]* 1 OOOO!, C[3]* 1E + O ~
1700 '
1710 PRINT
17 12 PRINT "
T
T
T"
1714PRINTU
R
ACTUAL
CALC
ERROR"
17 16 PRINT " -------- --------- ---------- --------1718 P$= " # # # # # # #
####.##
####.##
####.##"
1720 FOR L = l T O N
1730 X=LOG(R(L))
1740 TCALC= 1/(C(l)+C(2)*X+C(3)*X*X*X)-273.15
1760 PRINT USING P$;R(L),T(L),TCALC,T(L)-TCALC
1780 NEXT L
******************* program end ........................
1890 REM
1892 END
************* Begin Subroutines ****************
2000 REM
2010 REM
**** Invert 3 x 3 matrix "A" by cofactors ****
2020 GOSUB 2 160 : GOSUB 2 120
2030 DET=SUM
2040 FOR K = l T O 3 : FOR L = l T O 3
2050 GOSUB 2160
2060 FOR J = l T O 3 : B(J,L)=O : B(K,J)=O : NEXT J : B(K,L)=I
2070 GOSUB 2120
**** "E" = inverse = transpose of cofactor ****
2080 REM
2090 E(L,K)=SUM/DET
2100 NEXT L : NEXT K
2 110 R E T U R N
2120 REM
**** 3 x 3 determinant routine ****
2 130 SUM = B[l ,l]*B[2,2]*B[3,3]+B[1,2]*B[2,3]*B[3,1]+B[1,3]*B[2,1]*B[3,2]
2 140 SUM = SUM-B[1,1]*B[2,3]*B[3,2]-B[1,2]*B[2,1]*B[3,3]-B[1,3]*B[2,2]*B[3,1]
21 50 R E T U R N
2160 REM
**** Copy matrix A onto "scratch" matrix B ****
2170 FOR 1=1 T O 3 : FOR J=1 TO 3 : B(I,J)=A(I,J) : NEXT J : NEXT I
21 80 R E T U R N
---------I!
Appendix B
Sensing Current a n d Thermistor Selection
Introduction
Choosing t h e right sensing current depends on t h e range of temperature you want
to measure a n d t h e resolution you require a t the highest measured temperature.
T o correctly set the c u r r e n t switch you must understand how the thermistor a n d
the LDT-5910 interact a n d how temperature range a n d resolution values a r c i n h c r c n t
in the n a t u r e of thermistors.
Thermistor Range
Thermistors c a n span a wide temperature range, b u t their practical range is limited by their non-linear resistance properties. As the sensed temperature increases,
the resistance of t h e thermistor decreases significantly a n d the thermistor resistance
changes less f o r a n equivalent temperature change - t h e thermistor becomes less
sensitive. Consider the temperature a n d sensitivity figures below.
Tem~erature
Sensitivity
In the LDT-5910 the practical upper temperature limit is the temperature a t which
the thermistor becomes insensitive to temperature changes. T h e lower e n d of the
temperature range is limited by the maximum A / D i n p u t voltage of t h e LDT-5910.
Thermistor resistance a n d voltage a r e related through Ohms Law (V = I x R). T h e
LDT-5910 supplies c u r r e n t to the thermistor, either 10 u A or 100 uA, a n d as the
resistance changes a changing voltage signal is available to the thermistor inputs
of the LDT-5910. T h e LDT-5910 will over-range when the i n p u t voltage exceeds
about 4.5 Volts. Figure B-1 graphically shows t h e lower temperature a n d upper voltage limits f o r a typical 10 K o h m thermistor. T h e practical temperature ranges
f o r a typical 10 K thermistor ( a 10 K thermistor has a resistance of 10 K ohms
a t 25 " C ) a r e given i n t h e table below.
Sensing C u r r e n t
T e m p e r a t u r e Range
Temperature Resolution
You must also consider measurement resolution since the resolution decreases as
t h e thermistor temperature increases. T h e LDT-5910 uses a n A / D converter that
can sense a voltage change as small as 1 mV (1 mV is roughly equal to 1 A / D convertor step), to convert the input voltage to a digital number. T h e microprocessor then transforms the digital number to temperature using t h e Steinhart-Hart
equation. A temperature change of one degree centigrade will be represented by
LDT-5910 TEMPERATURE RANGE
(USING MPICAL I O K n P 25OC THERMISTOR)
- A/D OVE
-40
-20
0
20
40
60
80
TEMPERATURE (DECREES CELCIUS)
1OuA SENSE CURRENT
0
1OOuA SENSE CURRENT
FIGURE B-1 THERMISTOR TEMPERATURE RANGE
100
more A/D steps a t a lower temperature t h a n a t a higher temperature because of
the non-linear resistance of the thermistor. Resolution figures f o r a typical 10 K
o h m thermistor a r e given below.
Temperature
Voltage a t 10 uA
Resolution
For this thermistor a temperature change f r o m -20 to -19 " C will be represented
by 56 steps i n t h e LDT-5910's A / D convertor (if supplied with 10 uA). T h c same
thermistor will only change about 1.4 A / D steps f r o m 49 to 5 0 ° C !
T h e resolution you choose will impact the temperature displayed on the LDT-5910.
If you want to read a certain temperature accurate to . 2 " C , then you must set the
current switch f o r t h a t resolution. Since the thermistor is non-linear the resolution
will also decrease as the temperature increases. T h e high temperature limit occurs
when the temperature resolution drops below a n acceptable level.
Selecting the Sensing Current
T o select the c u r r e n t setting f o r a typical 10 K thermistor, determine the lowest
temperature you will need to sample a n d set the switch according to the range limits given above. If the temperature you w a n t to sample is below -10 " C you will
need to set the switch to the 10 uA setting. With the c u r r e n t switch set t o 10
u A t h e best resolution you will see will be a 0 . 2 " C temperature change. I f , f o r
example, the lower limit is 0 " C you can choose either setting, but t h e r e is a tradeoff in terms of resolution. If you need 0.1 " C resolution you will have to change
the setting of t h e c u r r e n t switch to 100 uA.
If you need high resolution over a narrow range, f o r a very accurate measurement,
you c a n set t h e current setting f o r the maximum resolution. For example, a t a high
temperature of 20 "C, you need a measurement resolution of a t least 0.05 " C . T h i s
resolution is w i t h i n the range of either current switch setting, b u t a t the 10 uA
setting the resolution is only 0.2 " C while a t the 100 uA setting the resolution is
better t h a n .05 " C . Set the switch to 100 uA.
Selecting and Using Thermistors
T h e type of thermistor you choose will depend primarily on the operating tempera t u r e range. These guidelines f o r selecting the range a n d resolution will apply to
a n y thermistor. F r o m f i g u r e B-1 you can also see t h a t 10 K thermistors a r e generally a good choice f o r most laser diode applications where high stability is required a t near room temperatures. Similarly, 10 K thermistors a r e o f t e n a good
choice f o r detector cooling applications where you w a n t to operate a t temperatures
f r o m - 4 0 ° C to room temperature. If you require a d i f f e r e n t temperature range or
the accuracy you need can't be achieved with either switch setting, select another
thermistor. Thermistor temperature curves, supplied by the m a n u f a c t u r e , show the
resistance verses temperature range f o r many other thermistors. ILX Lightwave
Corporation will also o f f e r help f o r your specific application.
Appendix C
Schematic Diagrams
Contents
LDT-5910 Main P W Analog
~
Section
LDT-5910 Main PWB Digital Section
LDT-5910 Front Panel PWB . . . .
LDT-5910 Power Supply PWB . . .
1227 GPIB /IEEE Interface . . . .
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65