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Experiment 1: Transducer Trainer Kit

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Experiment 1:

Transducer Trainer Kit


Indr Raj Gujjar 2016EE10453
Jitendra Vishwakarma 2016EE30517
Aman Singh 2016EE30515
Siddharth Kumar 2016EE30609

Aim :
• Study the working of various transducers on the Transducer trainer kit and plot the characteristics
of the transducers.

Equipment Required:
• DIGIAC 1750 Transducer and Instrumentation Trainer.
• 4mm Connecting Leads.
• Digital Multimeters

Part -1

Positional Resistance Transducers:

Objective:
 To draw the basic characteristics of output voltage against variable control setting.
 To describe the effect on the output voltage of loading the output circuit.

Theory:
A variable resistor consists of a "track" having a fixed overall resistance with a "wiper" which
can be moved to make contact with any point along the track.
It can be used to provide a variable voltage. A steady voltage is applied across the ends of the
fixed track. The wiper then picks off a variable voltage at the contact point with the track
(with respect to the end of the track). Used in this way the variable resistor is called a
potentiometer. And in this experiment we are going to learn about various experiments on
potentiometer.
Variation of Output Voltage with Setting of Rotary Potentiometer:

Circuit Diagram:

Readings:

Control 1 2 3 4 5 6 7 8 9 10
Setting
V out 0 1.6 3 4.13 5.19 6.62 8.19 9.65 10.82 11.91

Vout Vs Control Setting

14

12

10

8
Series1
6

0
0 2 4 6 8 10 12

Voltage across this section (V9 - V2) = 9.22 V


Voltage per division ( (V9 –V2)/(9-2) ) = 1.31 V

Variation of Output Voltage with Setting of Slide Potentiometer:

Circuit Diagram:

Readings:

Control 1 2 3 4 5 6 7 8 9 10
Setting
V out -5 -3.79 -2.66 -1.48 -.21 .91 1.99 3.03 4.06 4.99

Vout vs Control Setting:

0 Series1
0 2 4 6 8 10 12
-2

-4

-6
Resistance R9 = 10.6kΩ
Resistance R2 = kΩ
Resistance between settings 9 & 2 = R9 - R2 = kΩ
Voltage between settings 9 & 2 = V9 - V2 =7.85 V
Voltage per kΩ = V/kΩ
Effect of Loading on the Potentiometer Output Voltage:

Circuit Diagram:

Control 10 9 8 7 6 5 4 3 2 1
Setting
Output 5.85 5.85 5.81 5.77 5.72 5.66 5.49 5.16 3.65 1.36
Voltage(V)
Load 105.8 93.15 89.6 80.2 58.2 44.9 33.12 18.94 8.3 1.7
Resistance(k
ohms)

Output Voltage Vs Load Resistance:


7

0
0 20 40 60 80 100 120

Multimeter reading with the moving coil meter connected = 4.51 V

Loading resistance of the Moving Coil Meter = 17 kohms

After using buffer amplifier:

Output Voltage(digital) = 5.85 V

Output Voltage(Analog) = 6 V

Servo Potentiometer:
It is special positional potentiometer which is mounted on the experiment board which has a very large arc of
turning, approaching 360°.

Readings:

Maximum Positive Voltage is 5V and it occurs at 172.5 degrees.

Control 150 120 90 60 30 0 -30 -60 -90 -120 -150


Dial
Setting
Output 4.51 3.6 2.662 1.761 .891 .006 -.863 -1.732 -2.598 -3.48 -4.361
Voltage

Output Voltage Vs Control Dial Setting:

5
4
3
2
1
0
-200 -150 -100 -50 -1 0 50 100 150 200
-2
-3
-4
-5

Results:
In this experiment we learned about the different types of potentiometers(Rotary
Potentiometer,Slide Potentiometer,Servo Potentiometer).and plotted their characteristics of Vout
Vs control dial setting and they were linear in nature. And the curve of output voltage Vs load
resistance in case of loading was not linear.

Part-II

Wheatstone Bridge Measurements

Aim: Applying null method to measure unknown resistance and voltage.

Theory:
Wheatstone Bridge Circuit:
During measurement, R3 is adjusted until there is no current (Im) flowing in the galvanometer
circuit. The galvanometer current is zero or "null". Under these conditions, the bridge is said to be
"balanced". Hence the term "null balance".This condition is used to measure unknown resistance R4.

R4 = R2 /R1 x R3

In the Three Wire Resistance Measuring Circuit the three wire arrangement is used to reduce the
extra resisitance which is included in the measurement of R4 when we measure normally.

Measurement of Resistance:

Circuit Diagram:

Readings:
Dial reading = 221

Resistance R3 = 10 x dial reading = 2.21kΩ , Resistance R1 = 10,000 - R3 =7.79 kΩ , Resistance R2 =


12,000Ω ,Unknown resistance Rx = R2 /R1 x R3 =3.40 kΩ
10kΩ Resistor Dial Reading at R3(kΩ) R1(kΩ) R4(kΩ)
Setting Balance
10 86 .86 9.14 1.129103
9 163 1.63 8.37 2.336918
8 231 2.31 7.69 3.604681
7 291 2.91 7.09 4.925247
6 343 3.43 6.57 6.26484
5 391 3.91 6.09 7.704433
4 430 4.3 5.7 9.052632
3 461 4.61 5.39 10.26345
2 486 4.86 5.14 11.3463
1 498 4.98 5.02 11.90438

Measurement of Voltage Using Method 1:

Circuit Diagram:

Readings:
Unknown Dial Reading Calculated Voltage(V)
Voltage(V)
4 253 4.0583
3.5 291 3.4923
3 341 2.9892
2.5 403 2.5142
2 503 2.056
1.5 663 1.5124
1 991 1.101

"Unknown" Voltage:
When connected to the bridge = 2.612 V

Disconnected from the bridge = 3.421 V

Measurement of Voltage Using Method 2:


Circuit Diagram:

Unkown Voltage = 1.21 V

Unkown .25 .40 .60 .70 .80 .95


Voltage
Input
Dial Reading 91 163 253 271 328 396
at Balance

Results:
In this experiment we calculated the value of unknown resistance(R4) for different values of
setting.Graph of value of R4 against setting is plotted and graph comes out to be linear .and
measured unknown voltage using 2 different methods.

Part -III

Temperature Measurement:
Aim :
 To discuss the characteristics of an NTC thermistor.
 To discuss the characteristics of NTC thermistor bridge circuits.
 To discuss characteristics of a thermocouple.
 To deduce temperatures from a voltage reading across a transducer.

Theory:
In temperature transducers the active transducers are mounted within a clear plastic
enclosure which contains a heater. The heated enclosure is provided to raise the temperature
of the sensor transducers to allow measurements to be taken during experiments.

The Platinum RTD Transducer:

It consists a thin film of platinum deposited on a ceramic substrate and having gold contact plates at
each end that make contact with the film. The platinum film is trimmed with a laser beam to achieve
a resistance of 100Ω at 0o C and it has a positive temperature coeffiscient.
Rt = Ro + 0.385t
Rt = resistance at temperature t°C Ro = resistance at 0°C (= 100Ω)

The NTC Thermistor:


The thermistor (thermally sensitive resistor) is manufactured with the intention that its value will change with
temperature. Unlike a normal resistor, a large coefficient of resistance (change of resistance with temperature)
is desirable.
Diagram:
Characteristics of an LM335 IC Temperature Sensor:

Circuit Diagram:

Readings:
Time(minutes 0 1 2 3 4 5 6 7 8 9 10
)
Voltage(V) 3.11 3.21 3.251 3.283 3.312 3.332 3.361 3.382 3.391 3.398 3.426
Tempe 311 321 325.1 328.3 331.2 333.2 336.1 338.2 339.1 339.8 3.426
rature oK

38 48 52.1 55.3 58.2 60.2 63.1 65.2 66.1 66.8 69.6


oC

Characteristics of a Platinum RTD Transducer:


Circuit Diagram:
Readings:

Voltage for ambient temperature =3.38 V

Time(minutes) RTD Resistance RTD Temperature


oK oC

0 114 324 51
1 115 324.2 51.2
2 117 327.3 54.3
3 119 332.1 59.1
4 121 337.4 64.4
5 122 340.1 67.1
6 123 343 70
7 124 345.1 72.1
8 125 346.1 73.1
9 125 347.8 74.8
10 125 348.2 75.2

RTD Resistance( ohms) Vs RTD Temperature(0C)


126

124

122

120

Series1
118

116

114

112
0 20 40 60 80

Characteristics of an NTC Thermistor:

Circuit Diagam:

Readings:
Time(minutes) Dial Reading Voltage Temperature Thermister
for 2.5 V oK oC Resistance
0 0.201 3.231 323.1 50.1 3.01
1 0.191 3.254 325.4 52.4 2.91
2 0.17 3.281 328.1 55.1 2.7
3 0.14 3.336 333.6 60.6 2.4
4 0.12 3.372 337.2 64.2 2.2
5 0.091 3.402 340.2 67.2 1.91
6 0.082 3.42 342 69 1.82
7 0.07 3.452 345.2 72.2 1.7
8 0.062 3.476 347.6 74.6 1.62
9 0.054 3.491 349.1 76.1 1.54
10 0.046 3.503 350.3 77.3 1.46

Thermister Resistance Vs Temperature

3.5
3
2.5
2
1.5
1
0.5
0
0 10 20 30 40 50 60 70 80 90

Characteristics of NTC Bridge Circuits:

Circuit Diagram:
Readings:
time Voltage Temperature Bridge Output
k C 1 active NTC 2 active NTC
0 3.152 315.2 42.2 0 0
1 3.232 323.2 50.2 91.23 104.6
2 3.252 325.2 52.2 260.2 206.23
3 3.28 328 55 416 231.5
4 3.312 331.2 58.2 561 463
5 3.32 332 59 662 647
6 3.341 334.1 61.1 759 794
7 3.361 336.1 63.1 823 923
8 3.39 339 66 881 1023
9 3.401 340.1 67.1 943 1101
10 3.42 342 69 961 1162

Ouput Voltage(V) VS Temperature(0C)

3.45

3.4

3.35

3.3

3.25

3.2

3.15

3.1
0 20 40 60 80
Results:

In this experiment the resistance of RTD transducer and NTC thermistor is pltted against
temperature .For RTD tranducer the plot comes out to be linear with positive slope indicating it
has positive temperature coefficient and for NTC thermistor plot comes out to be linear with
negative slope indicating it has negative temperature coefficient.

Part -IV

Linear Position or Force Applications


Aim:
 To characterise Linear Variable Differential Transformer (LVDT). „
 To characterise a linear variable capacitor. „
 To characterise a strain gauge.

Characteristics of a Linear Variable Differential Transformer

Diagram:

Readings:

Core Position(turns from Output Voltage


neutral)
Digital Meter Analog Meter
-4 458 4
-3 388 3.5
-2 286 2.5
-1 142 1
0 11.2 0
1 174.3 2
2 31541 3
3 422 4
4 496 4.5

Analog Meter Voltage Vs Core Position:

5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
-6 -4 -2 0 2 4 6

Characteristics of a Variable Capacitor Transducer

Circuit Diagram:

Readings:

Turns Of 0 1 2 3 4 5 6 7 8 9 10
Screw
Output 0 .386 .590 .881 1.211 1.327 1.521 1.749 1.928 2.122 2.301
Voltage(V)
Output Voltage Vs Turns Of Screw:

2.5

1.5

Series1
1

0.5

0
0 2 4 6 8 10

The Strain Gauge Transducer

Circuit Diagram:

Readings:

No. of 0 1 2 3 4 5 6 7 8 9 10
coins
Output 1 1.9 3.1 4 3.5 4 4.8 5.1 6 6.5 7
Voltage(V)
Output Voltage Vs No. of Coins:

0
0 2 4 6 8 10 12

Characteristics of a Strain Gauge Transducer

Circuit Diagram:

Readings:

No. of 0 1 2 3 4 5 6 7 8 9 10
coins
Output 0 1 1.5 2 3 3.5 4 5 5.5 6 6.5
Voltage(V)
Output Voltage VS No. of coins:

4
Series1
3

0
0 2 4 6 8 10 12

Results:
For Variable capacitor transducer,output voltage is obtained by having different number of
turns which changes value of capacitor and graph is plotted between them which comes out
to be linear.
For strain gauge transducer ,output voltage is obtained for different loads(coins) which
leads to change in value to fine wire resistance.Graph of output voltage and load comes out
to be linear with positive load.
For LVDT , core position is varied with respect to neutral position and analog and digital
ouputs are observed.Graph of analog voltage ouput vs position is plotted and the voltage
comes out to be minimum near neural and increases as position is changed in either
direction.

Part -V

Mathematical Operations
Aim: To study about characteristics of a summing amplifier and an integrator. „

Characteristics of a Summing Amplifier

Circuit Diagram:
Readings:

Maximum possible output voltage=9.93 V

Inputs(V) Output
A B C -(A+B+C) Measured O/p
1 1 1 -3 -3.129
2 1 3 -6 -5.97
-3 4 2 -3 -3.115
3 5 4 -12 -12.156
-3.5 2.7 -1.4 2.2 2.212

Characteristics of an Integrator:

Circuit Diagram:

Readings:
Maximum Output Voltage = 10.65 V

Switched Input Reference No. of time time taken to Calculated


Time Voltage(V) Voltage(V) constants reach ref.(s) Time constant
Constant
1s 1 10 10 10 1
100 ms 1 10 10 1.84 0.184
100 ms 0.2 5 25 3.35 0.134
10 s 5 2 0.4 4.53 11.325

Results and Conclusion :

In this part we checked the output of Summing amplifier with the theoretical ones(-
(A+B+C)) by giving 3 inputs A ,B, C and and it comes out to be approximately same.
And it next part we calculated time constant using reference voltage and time taken to
reach reference voltage.

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