Download XEN-5310vac

Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
Features
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Calibration curve for air
Analog + Digital output
Measurement with proven Thermal Conductivity
Gauge XEN-TCG3880
Read-out with dedicated ASIC chip for biasing
and measuring the sensor components
Start-up time: 1 second
Reaction time: 1 second
Operation: 5 V @ 20 mA
Dual Analog output
Digital output (RS232 @ 3.3 V)
Calibration curve for selected gases optional
XEN-5310 vacuum sensor,
approximately real size (58×25 mm)
Applications
 Examples:
-
Description
The Xensor XEN-5310 is an intelligent gas sensor for with application to vacuum measurement in
the range of 1 mPa to 10 kPa (standard atmospheric pressure: 101.325 kPa), based on the
measurement of the thermal conductivity of the ambient gas.
To compensate for the influence of temperature it is measured separately and a correction is
made in the micro-controller.
Each device is factory calibrated, with the option of recalibration by the customer.
Block Diagram
TCGauge
Connector
Analog out
Digital IO
ASIC
Micro-controller
LED indications
Pt100
Voltage regulator
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 1 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
Preliminary Specifications (at 23 ˚C, 0% RH)
Item
Vacuum sensing
Sensing range
Digital output
Sensing resolution
Sensing resolution
Pressure indication inaccuracy
Low pressure sensitivity (air)
10 m-10 k
0-100k
0.05
0.01
5
4.7%
Operating limits
Temperature operating range
-20 to + 55
Operation speed
System start up time
T90 response time
T10 recovery time
Data update rate
Electrical
Current consumption
Supply voltage
Output signals
Digital
Analog signal: air pressure
Storage
Temperature storage limits
Humidity storage limits
Typical
1
1
1
1
20
5-10
1-3
10-40
20-70
Unit
Remarks
Pa
Pa
V/W
Pa
%
%/Pa
Analog output 1 V to 3 V for air
Air or selected gas
Peak-to-Peak Noise level (8σ)
Near 0 Pa
Between 1 Pa and 1 kPa
Reduction in output signal
ºC
Calibration for Room Temperature
Second
Second
Second
Hz
mA
V
V
copyright Xensor Integration
RS232 @ 3.3 V
0.001-100 kPa logarithmic
ºC
%RH
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
100 mW @ 5 V
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 2 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
Functional description
The Xensor XEN-5310 calculates the absolute pressure below atmospheric pressure. This is done
by measuring the thermal conductivity of the ambient air using a thermal conductivity gauge
(TCG), and comparing this to the factory calibration measurement. To eliminate the influence of
temperature it is measured separately, and a compensation is made by the micro-controller. The
corrected output signal is then compared to the standard calibration curve for reduced pressures
of air, and from this the pressure is determined.
Selectivity
Although the XEN-5310 is standard calibrated for air, the residual gas in a vacuum system may be
of different composition. In that case the reading of the sensor will be wrong, see Fig. 3. This can
be user-corrected by either having the analog pressure output calibrated for the correct gas, or
use the digital pressure output for the correct gas, or alternatively use the digital transfer output
and calculate the pressure using parameters for the gas present in the vacuum system.
Standard calibration curve
The relation between pressure and transfer of the sensor, i.e., the output voltage of the XEN-TCG3880Pt100-roof, divided by the input heating power, can be approximated by a simple formula,
depending on a few –measured- constants. The measured and calculated curves for air are
shown in Fig. 2, the relative difference between the measured and calculated transfer is less than
2% over the entire range. For clarity, calculated points are shown for different pressures than the
measured points. However, this is for the ideal case, when we exactly know the transfer at zero
pressure and at atmospheric pressure. In practice these data are not always precisely know, and
larger errors can occur, especially at very low pressures (below 1 Pa) and high pressures (above
1000 Pa). In general between 0.1 Pa and 10 kPa a fairly accurate reading can be expected at
room temperature, though. Assuming the gas being measured is air, or the curve is adapted for
the gas being measured.
Figure 2: The measured Transfer of the XEN-5310 TCG-sensor (output voltage divided by input
heating power in V/W) as a function of pressure, and the approximated curve from the pressure
dependent formula.
The formula to calculate the pressure is obtained by the following extraction method, based on
the transfer at zero pressure, the sensitivity at low pressures (for instance, the output signal at
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 3 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
around 0.5 Pa, divided by this pressure), and the output signal at atmospheric pressure. And
finally, two transition pressures are derived by curve fitting.
Then the method goes as follows:
The residual membrane conductance Gmem is calculated by inverting the zero-pressure transfer:
(1)
Gmem = 1/Transfer0 Pa
The total conductance Gtot is at any pressure the inverse of the transfer and is the sum of the
membrane conductance and the gas conductance (this is a simplification that may not be physically correct, but yields a good working formula):
(2)
Gtot = 1/Transfer = Gmem + Ggas
The low-pressure sensitivity Go is calculated at a low pressure P around 0.5 Pa:
(3)
Go = Ggas≈0.5 Pa/P≈0.5 Pa = (Gtot - Gmem)≈0.5 Pa/P≈0.5 Pa
The sum of the transition pressures Pt1 and Pt2 is calculated by dividing the transfer at high
pressure by the low-pressure sensitivity:
(4)
Pt1 + Pt2 = 2×(Gtot - Gmem)100kPa/ Go
Then the approximating curve for the inverse of the transfer, the total conductance G tot, is given
by:
(5)
Gtot = Gmem + Ggas = Gmem + Go {½P×Pt1/(P+Pt1) + ½P×Pt2/(P+Pt2) }
In the low pressure limit, this formula approaches the formula for gas conductance that is proportional to pressure:
(6)
Gtot, low pressures = Gmem + Go P
In the high pressure limit, this this formula approaches the formula for gas conductance that is
independent of pressure:
(7)
Gtot = Gmem + Go {½ Pt1+ ½ Pt2}
Fig. 2 shows a measurement for the XEN-TCG3880 roof with a heat sink on top of the membrane (roof) at 100 µm distance, and the calculated curve with the following parameters:
Parameter
Value
Units
Remarks
Measured
Transfer at zero pressure
Transfer at low pressure
Transfer at atmospheric pressure
133.32
130.49
21.63
V/W
V/W
V/W
At 0.456 Pa air pressure
For air
Calculated
Gmem
Go
Pt1 + Pt2
7.50
0.3568
217.1
mW/V
mW/V/Pa
Pa
For air
Curve-fitted
Pt1
Pt2
17.5
199.6
Pa
Pa
Curve fitted
Curve fitted
In the ideal case, the values of Pt1 and Pt2 are determined by distances between the membrane
and the heat sinks on either side, and would be close to the pressure where the mean-free-path
between collisions equals that distance. In the XEN-TCG3880 this is not the case, as shown by
the relatively low values of the transition pressures. This is attributed to the 3-D like behavior of
this sensor.
As the parameters Gmem, Go and Pt1 + Pt2 will all depend somewhat on temperature, this will
lead to errors in the calculation of the pressure as temperature changes. And for gases other
than air, the parameters Go and Pt1 + Pt2 will need to be adjusted.
An example of how the output and transfer changes for other gases is shown in Fig. 3, for a
sensor without the roof.
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 4 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
Figure 3: The output voltage of the XEN-TCG-3880 sensor for 4 different gases.
In Fig. 3 it is noteworthy that zero pressure, the Gmem for all gases is the same as it should be,
and that at low pressures the Go for helium, nitrogen and carbon-dioxide are virtually the same,
while argon is less sensitive. Near atmospheric pressure helium shows the most sensitivity,
while carbon-dioxide tends towards the same output as argon and even crosses its curve. So,
the sum of the transition pressures Pt1 + Pt2 will be different for each of these 4 gases.
Electrical characteristics
The sensor requires a nominal supply of 5-10 V and about 20 mA at room temperature. This
supply voltage is converted to the internal operating supply of 3.3 V. The minimum and maximum supply voltages are 4 V and 20 V, the sensor will stop operating when a voltage of less
than approximately 3.5 V is supplied. Such low power supply voltages are not recommended,
as the operation of the hydrogen sensor is no longer complete (for instance, the sensor can no
longer display the analog signal up to 3 V).
A power supply of more than 30 V will lead to destruction of components and thus of the hydrogen sensor. It is recommended to have the supply voltage close to 5 V, any excess voltage will
be converted into heat dissipation, possibly causing thermal drift of the sensor.
Trouble Shooting
In case of trouble:
 First try to get the sensor to work again by disconnecting and connecting the power supply.
 If the sensor will still not operate properly then contact the manufacturer:
call +31 15 2578040 or email [email protected].
Physical dimensions and connections
The sensor is standard supplied with an 8-terminal 2-row micro-fit connector, with on the bottom
row the power supply and the analog output signals. On the top row the RS-232 signal lines and
an additional ground connection are situated.
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 5 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
If so desired, the sensor can also be supplied with a 4-terminal single row connector, omitting the
RS-232 connection.
Furthermore, if so desired a 3-wire connection is possible with only a single analog output, where
a modulation on the analog signal output will be installed instead of on the analog alarm output.
Physical geometry of the PCB, top view and view from connector side:
58.4 mm
9 mm
3.2 mm mounting holes
connector
capacitor
20.3 mm
38.7 mm
TCG
10 mm
25.4 mm
14 mm
Connections of the 2-row 8-pin AMP connector, view from outside of board:
Tx
Gnd Rx
Out1 Gnd Out0 Vdd
Printed Circuit Board thickness 1.6 mm, components on both sides. All components are less
than 3 mm high, except for the connector, TCG and buffer capacitance.
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 6 of 7
Vacuum sensor
XEN-5310
Intelligent Thermal Conductivity Gauge Vacuum Sensor
Preliminary datasheet
Order Information and Accessories
The order code for the standard version of the vacuum sensor XEN-5310, CE approved, is given below, with options.
Standard version: XEN-5310-A8-C1-T2055-Vac-NoH-NAT
Options for vacuum sensor XEN-5310
Option
Choice
Code
Content
Availability
RS232
Yes
No
A8
A4
AMP 2x4 connector (AMP or compatible)
AMP 1x4 connector (AMP or compatible)
Standard
On request
Cable pack
No
Yes
Yes
Yes
C0
C1
C2
C3
No Cable pack
Cable connector + separate contacts not assembled
Cable connector with 25 cm wires bare-ended
Customer specification
Standard
Standard
Standard
On request
Temperature range
Normal
Extended
T2055
T4065
-20 to +55 °C
-40 to +65 °C. In combination with SEN option
Standard
Soon
Analog output
Pressure
Leak
Full
Other
Vac
4%
100%
?%
0-100 kPa
0-4% hydrogen, alarm 1%
0-100% hydrogen, no alarm
Customer specified
Standard
Not for vacuum
Not for vacuum
On request
Humidity sensor
Standard
Standard
High-accuracy
NoH
ALP
SEN
No humidity sensor
Alps sensor
Sensirion sensor
Standard
Not for vacuum
Not for vacuum
ATEX
No
Yes
NAT
ATX
PCB-version
ATEX conform
Standard
Soon
Other options
Inquire
Customer-specific alterations
On request
Accessories for the XEN-5310 vacuum sensor, available separately.
FTDI readout PCB with FTDI interface chip to connect up to 4 sensors to a PC via USB
Cable pack 2 AMP-connector 4 or 2x4 rows, Teflon-insulated wires 25 cm, bare ended
Cable pack 3 One of the options is a cable of length to be specified, with AMP connectors 2x4
rows on both sides, for connection of the sensor to the FTDI PCB.
FieldOff
Field Offset Nulling Set: FTDI readout + Cable pack 3 + software, to null offset
LabCal
Lab Calibration Set: FTDI readout + Cable pack 3 + software, to completely
recalibrate the vacuum sensor. This requires customer facilities such as a vacuum system with accurate pressure measurement.
Disclaimer: No responsibility is taken for the consequences of improper functioning of the sensor.
Conditions: Use of sensors for industrial applications is subjected to patent rights. Xensor Integration assumes no liability
arising from violation of these rights
Warranty: Xensor Integration warrants its products against defects in materials and workmanship for 12 months from
date of shipment. Products not subject to misuse will be replaced or repaired. The foregoing is in lieu of all
other expressed or implied warranties. Xensor Integration reserves the right to make changes to any product
herein and assumes no liability arising out of the application or use of any product or circuit described or
referenced herein.
Xensor Integration bv
Distributieweg 28
2645 EJ Delfgauw
The Netherlands
copyright Xensor Integration
Smart Sensor Devices
Phone +31 (0)15-2578040 Founded 18 May 1988 ABN-AMRO 60 50 40 311
Fax
+31 (0)15-2578050 Trade reg. 27227437 IBAN NL42ABNA0605040311
Email
[email protected] Site
www.xensor.nl VAT NL 009122746 B01
14 October 2014
page 7 of 7