Download opamp application using lm335-semiconductor temperature sensor

BME 325
MEDICAL ELECTRONICS
OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR
TEMPERATURE SENSOR
EXPERIMENT 04
OPAMP APPLICATION USING LM335-SEMICONDUCTOR
TEMPERATURE SENSOR
Objective:
The aim of this experiment is the realization of a celcius thermometer using Lm335 series
semicondutor temperature sensor and measuring various temperatures, comparing the results
intended. Sensor output voltage must be set to show ° c unit on the screen of the multimeter
using opamp circuits (amplifiers and adder, and so on).
Theory:
LM335 is a precision, easily calibrated, integrated circuit temperature sensor with an
operating range of -40oC to 100oC. The low impedance and linear output makes interfacing to
a control circuit simple. The sensor comes in a TO-92 package and provides an output voltage
directly proportional to the absolute temperature at the rate of +10mV/oK. The output is
calibrated with an external potentiometer to provide a 2.98 V output at 25oC. When calibrated
at 25oC, the LM335 has an error of less than 1oC over a 100oC range. Output at ant
temperature can be calculated using the formula below
𝑇
𝑉𝑜𝑢𝑡 𝑇 = 𝑉𝑜𝑢𝑡 𝑇𝑜 𝑥
𝑇𝑜
Knowing output voltage at a reference temperature output voltage at any temperature is
calculated using equation. For example at 40°C output of the LM335 is 3.13Volts. Then the
output at 100°C is given by
V (100) = V (40) (273+100) / (273+40) = 3.13 x 1.19
= 3.724 Volts.
Preliminary Work:
1) Calculate LM335 output at 20,25,30,35 °C
Figure 1
1
BME 325
MEDICAL ELECTRONICS
OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR
TEMPERATURE SENSOR
2) In the figure a dc power source V2 is used instead of LM335 and it is output is 3.03V.
output of U1,U2 and U3 are indicated. Calculate the unknown values for the circuit in
figure 1 (including V3 DC source) so that the output voltage of the circuit will be
Output voltage equal
changetoper
degree change
in but
temperature
known
as temperature
sensitivity.
temperature
in °C
in mVs. isFor
example
at 40°C output
of the LM335 is
LM335 is designed
for 10mV/°C.
This makes
an ultra
sensitive
temperature
STS is 3.18Volts
approximately
3.13Volts
or atit45°C
output
of the
LM335 issensor.
approximately
biased using a but
regulated
power supply.
biasingby
current
is within 400µA
to 5mA
for and 45mV
the circuit
output The
measured
a multimeter
must be
40mV,
LM335 and family.
Figure 2 (for
shows
a STS
biased using
a dc power
supply.
A series resistor
respectively.
further
information
inspect
LM335
datasheet).
limits current (1.6mA) within the prescribed range.
!!! ANYBODY WHO DID NOT PREPARE PRELIMINARY WORK CAN NOT JOIN THE EXPERIMENT !!!
Procedure:
1) Calibrate LM335 as defined below.
Output voltage change per degree change in temperature is known as temperature
sensitivity. LM335 is designed for 10mV/°C. This makes it an ultra sensitive
temperature sensor. STS(semiconductor Tempereture Sensor) is biased using a
regulated power supply. The biasing current is within 400µA to 5mA for LM335 and
family. Figure 2 shows a STS biased using a dc power supply. A series resistor limits
tput voltage change per degree change in temperature is known as temperature sensitivity.
M335 is designed for 10mV/°C. Thiscurrent
makes it an(1.6mA)
ultra sensitivewithin
temperature
sensor.
STS is
the
prescribed
range. (If you want to use a single DC power
sed using a regulated power supply. The biasing current is within 400µA to 5mA for
source
for
the
positive
voltage
values
for
the whole circuit calculate the resistor value
+ Adj.
M335 and family. Figure 2 shows a STS biased using a dc power supply. A- series
resistor
mits current (1.6mA) within the prescribed
range.
that must be used instead of 5.6k)
Figure 1, Base Diagram LM 335
5.6K
9V
5.6K
LM335
Vo
9V
TP1
LM335
10K
Vo
- + Adj.
Figure
2 PinLM
Connection
Figure 1,
Base Diagram
335
Lm335
Figure 3
Figure 2, Biasing STS a) Uncalibrated b) Calibrated
5.6K
5.6K
STS output
is calibrated
to read exact temperature
in degree Kelvin using a potentiometer as
TP1
Vo
9V
LM335
Vo
10K
Table-1
shown in Figure 2. In this calibration
process the wiper of the potentiometer is connected to
Device
Temperature
the adjustment terminal.
Once calibrated
at oneRange
temperature the potentiometer is undisturbed.
Figure 2, Biasing STS a) Uncalibrated b)LM125
Calibrated
-55°C to 150°C
2) Construct the LM225
circuit in figure
3.125°C
For accurate results you are advised to use
-40°C to
Table-1
potentiometers LM335
so that you can
adjust
accurately.
-40°C
to 100°C
Device
Temperature Range
LM125
-55°C to 150°C
Family of STS
9V
LM335
LM225
LM335
-40°C to 125°C
-40°C to 100°C
Family of STS
STS output is calibrated to read exact temperature in degree Kelvin using a 10-turm trimpot
of the trimpot is connected to the
trimpot is undisturbed.
as shown
in exact
Figure
2b. Inin degree
this calibration
process
the wiper
S output is calibrated
to read
temperature
Kelvin using a 10-turm
trimpot
shown in Figure
2b. In this calibration
process
the wiper
of the trimpot
is
connected
to the
adjustment
terminal.
Once
calibrated
at
one
temperature
the
ustment terminal. Once calibrated at one temperature the trimpot is undisturbed.
measure theTo
temperature
the STS
make contact the
with the
surface
of body.
However,
measure
theshould
temperature
STS
should
make
contact with the surface
measure temperature of water or liquid STS is not dipped directly. The process of dipping
tothemeasure
water
or liquid
STS isliquid
not dipped directly. The
Liquid shorts
terminals oftemperature
the STS and STSof
may
spoil. Therefore
to measure
of body. However,
process of dipping
in Liquid shorts the terminals of the STS and STS may spoil. Therefore to measure liquid
2
BME 325
MEDICAL ELECTRONICS
OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR
TEMPERATURE SENSOR
3) Measure different temperetures in a range as wide as possible, compare your results
with a thermometer afill the table below and draw temrepereture vs. volts diagram for
the thermometer,sensor and circuit output.
Fill the report by necessary measured values and graphs
Question:
Explain the use and purpose of each opamp.
Equipment List:
•
•
•
•
•
•
3 741 Opamp
6 x 10 k , 1x5,6k, 1 x 1 k resistor,
3 x 10 k potentiometer
1 piece LM335 temperature sensor
Multimeter
Power supply (+15V,-15V,+9V,+5V)
3
Student ID # :
Name
:
BME 325
MEDICAL ELECTRONICS
OPAMP APPLICATION USİNG LM335-SEMICONDUCTOR
TEMPERATURE SENSOR
REPORT:
1.
V3 :
R1 : R5 : R2 : R6 : R3 : R7 : R4 : Sensor Output (V)
Tempereture (°C)
Measured
2.
(°C)
V
3. Answer of the Question
4
Calculated
Circuit Output
(V0)