Transducer for temperature measurement

Objective:

To calibrate a thermocouple
Equipment and accessories required
i) TK294A Instrumentation module
ii) Heat bar
iii) Thermometer
iv) Calibration Tank
v) Transducer thermocouple and flying compensating lead
vi) Power Supply
vii) Multi-meter

Introduction:
If two wires of dissimilar metals are in contact, an electromotive force exists. The value of this emf depends upon several factors including temperature. The junctions of this sort is used to measure the temperature are called thermocouple. The produced emf depends upon the types of thermocouple used. It is maximum for Sb-Bi thermocouple. The production of emf depends upon the distance in electrochemical series.
The Peltier effect is the presence of heating or cooling at an electrified junction of two different conductors and is named after French physicist Jean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors A and B, heat may be generated (or removed) at the junction.
Thomson effect was predicted and subsequently observed by Lord Kelvin in 1851. It describes the heating or cooling of a current-carrying conductor with a temperature gradient.
Relevant Equations:
Peltier effect,
eA-eB = P (ӨA – Ө B) … (1)
Here P is Peltier coefficient.
Thompson’s Effect,
e1 = T1 (ӨA- ӨB) … (i)
e2 = T2 (ӨA – ӨB) … (ii)
From (i) and (ii)
e2 – e1 = (T2-T1)(ӨA – ӨB) … (2)
T1 and T2 are Thompson coefficient.
From (1) and (2)
eA-eB + e2 – e1 = (P+ T2 –T1)(ӨA – Ө B)
or, E = k (ӨA – Ө B)
Here, E = eA- eB + e2 – e1
And, k = (P+ T2 –T1)

Experimental Setup:

OBSERVATION TABLE
Notch Number Tank Temperature(in ℃) Room Temperature (in ℃) Temperature Difference Voltmeter Reading(in V) TC emf (in mV)
22 34 27 7 2.400 0.0024
20 38 27 11 2.411 0.002411
18 42 27 15 2.446 0.002446
16 45 27 18 2.449 0.002449
14 50 27 23 2.457 0.002457
12 54 27 27 2.471 0.002471
10 59 27 32 2.481 0.002481
8 65 27 38 2.487 0.002487
6 71 27 44 2.500 0.002500
4 80 27 53 2.512 0.002512
2 95 27 68 2.520 0.002520

Data Analysis

Result:
Slope of the approximating line = 210^-6 mV/℃
= 210^-3 μV/℃
It is the thermocouple constant.

Discussion:
In this experiment, we calibrated the thermocouple. We observed different values of emf produced for different differences between two junctions. The emf so produced was small, so we amplified and observed using voltmeter. The graph was drawn between produced emf and difference in temperature. In actual, curve should be linear but in our practical, it was deviated from it. An equivalent line was used to approximate the curve and slope was calculated.
The difference in the ideal condition and practical was due to human error, inaccuracy to measure temperature by thermometer to required limit, sensitivity of instrument etc.

Conclusion:
It was concluded that the emf produced is dependent on the difference in the temperature between two junctions. By the above method, we can observe and calculate such phenomenon. Thermocouple constant can be calculated.

References:

1. https://community.keysight.com/community/keysight-blogs/general-electronics-measurement/blog/2017/01/16/transducers-for-making-temperature-measurements-with-a-dmm

2. http://www.electronics-tutorials.ws/io/io_3.html