1. ENGR 202 – Winter 2016
Lab 4: Capturing Temperature Measurements with a
Thermocouple
Professor: Dr. Roger Marino
Lab Instructor: Steven Pagano
Section 69
Group 07
Members:
Yifang Wang
Dayun Piao
Letao Wu
Due Date: 3/11/16

2. 1
I. INTRODUCTION
In order to capture a wide range of temperature, a thermocouple was used to perform this
experiment. Thermocouple is a sensor of measuring temperature. Therefore, in order to capture
the correct data for data analysis, it is essential to set up the thermocouple correctly and pay
attention to temperature change. And after conducting this experiment, we were expected to
know how to set up the thermocouple correctly and understand its application on measuring
temperature.
Purpose of the Experiment
The purpose of the experiment is to help students understanding the application of thermocouple
on measuring a wide range of temperature and getting an idea how fast or how slow the
temperature change through data analysis.
II. EXPERIMENTAL PROCEDURE
A. Equipment
Table 1: Equipment used to measure temperature
NI USB TC-01 Thermocouple Measurement Device
Type K thermocouple, Omega KTSS-HH
Power resistor, 100 Ω, 25 Watt
Hewlett Packard E3631A DC power supply
B. Procedure
Before any measuring can be done, the power supply must be set up. Two alligator clips must be
connected to the positive and negative terminals of the power supply. Then, set the voltage
output to 16 volts. Next, plugging the thermocouple into the computer should bring up the NI
software required to take measurements. Temperature must be set to Celsius and the type must

3. 2
be set to K. Once the ambient temperature stabilizes, record the value for reference. Next, the
resistor must be connected to the power supply via the alligator clips. The resistor will begin to
heat up, and the thermocouple should be inserted to monitor its temperature. Also be aware that
the thermocouple should not touch the sides of the inside of the resistor. Once the temperature
inside the resistor is steady (66 - 77 degrees C), data logging can begin.
On the software, click “Start data logging” and proceed to remove the thermocouple from the
resistor. The thermocouple should be held upright with no waving to prevent interference of the
cooling process. The data logging should continue until the temperature reads the same as the
ambient temperature from the start. The log can then be saved and this process is to be repeated
two more times to obtain three solid cooling curves. When finished, turn off the power supply
and put the equipment away.
C. Front Panel of Temperature Measurement
Figure 1: Front Panel of Temperature Measurement of Trial 1

4. 3
Figure 2: Front Panel of Temperature Measurement of Trial 2
Figure 3: Front Panel of Temperature Measurement of Trial 3
III. RESULTS
Table 2: Data analysis of temperature for three trials

5. 4
Figure 4: Graphical method to compute the time constant trial 1

6. 5
Figure 5: Comparison of actual temperature and modified temperature of trial 1
Figure 6: Comparison of actual temperature and modified temperature of trial 2
Figure 7: Comparison of actual temperature and modified temperature of trial 3

7. 6
Summary of Results
The table 2 shown above was the result summary of cooling temperature analysis. We got the
initial temperature and ambient temperature by observing the temperature data on steady state
and the temperature close to room temperature. In order to calculate the time constant, we used
the equation LN((T(t)-ambient T)/(initial T-ambient T))=(-tao/t) to rearrange the measuring
temperature, then use the scatter plot to get a graph that shown as Figure 4 above. Finally, we got
the linear equation by fitting a linear trendline in excel. Similarly, we got the time constants of
trial 2 and trial 3 So we could calculate the time constant with the slope known. With the
computed time constant in each trial, we got the modified temperature by substituting the time
constant into this equation T(t)=ambient T + (initial T - ambient T)* exp(-tao/t). The resulting
graphs were figure5,6 and 7 shown above. By comparing those three graphs, the modified
temperature with computed time constant 69.4 second in trial 3 fitted the actual data well, which
indicated that the computed time constant in trial 3 was the most closer value to the real time
constant. As for figure 5 and 6, the modified temperature fitted the actual data better if the actual
data was getting closer to the ambient temperature. As for the rate change of temperature in
different stages, we got the the rate change in steady state was 0 in all three trials. In trial 1 and 2,
the rate change in mid rise or mid fall were close to each other. However, by comparing three
trials, the rate change for the temperature was highest.
Discussion
The advantages are obvious. As we all know, the cold junction compensation is a method to
reduce the error caused by measuring environment. Technically, the temperature of resistor
should be measured at 0 ℃ as a standard method. Using the circuit can amend the potential
difference caused by indoor temperature. Additionally, the circuit can also mimic the reference
junction. On the other side, we can also find some disadvantages. The circuit is actually a
conditioning stage which means it is not efficient and utility for any measurement.
Thermocouple provide very small signals which are usually susceptible to noise, and the
differential inputs will reject common mode voltage. Therefore, differential input channel can
provide a more stable reading in this situation. On the other hand, single ended channel has only
one low wire, which will affect the accuracy dramatically. This is why we choose differential
input channel thermocouple.
The reason for setting up the voltage measurement task is that the sensing thermocouple is base
on the seebeck effect. The voltage is proportional to the difference of the temperature at the two
junctions.

8. 7
The accuracy of the thermocouple is 0.1 degree celsius. If the omega thermocouple touched the
resistor, this would affect the measuring temperature. And we can use error propagation to
estimate the error in the temperature reading since we know the relationship between the
measuring temperature and time. As a result, we can apply derivative function to calculate the
uncertainty of temperature.
The exponential cooling model fits the data we recorded from experiment perfectly.
Conclusion
From this lab, we learned and practiced how to measure temperature by using thermocouple. The
differential input channel is also required to resist the noise from environment. The principle of
TC and the two methods of cold junction compensation are also proved during the lab. We
analyzed data and calculated the time constant of cooling curve, and modified the temperature
with a calibration curve as well. All the graphs and results fit the exponential cooling model and
Newton’s Law of cooling completely.
IV. APPENDIX

9. 8
Figure 8: Graphical method to compute the time constant in trial 2
Figure 9: Graphical method to compute time constant in trial 3

10. 9

11. 10

12. 11

13. 12
90 41.3 '7.88E'01 3.69E+01 58.3 '9.82E'01 3.63E+01 37.1 '8.55E'01 3.53E+01
91 40.9 '8.12E'01 3.67E+01 57.9 '1.01E+00 3.61E+01 37 '8.79E'01 3.51E+01
92 40.7 '8.24E'01 3.65E+01 57.5 '1.02E+00 3.60E+01 36.8 '8.91E'01 3.50E+01
93 40.4 '8.42E'01 3.64E+01 57 '1.04E+00 3.58E+01 36.7 '9.10E'01 3.48E+01
94 40.1 '8.61E'01 3.62E+01 56.5 '1.06E+00 3.56E+01 36.5 '9.29E'01 3.47E+01
95 39.9 '8.73E'01 3.60E+01 56 '1.07E+00 3.55E+01 36.4 '9.42E'01 3.45E+01
96 39.7 '8.86E'01 3.59E+01 55.4 '1.08E+00 3.53E+01 36.3 '9.55E'01 3.44E+01
97 39.4 '9.06E'01 3.57E+01 54.9 '1.10E+00 3.51E+01 36.2 '9.75E'01 3.43E+01
98 39.1 '9.26E'01 3.56E+01 54.3 '1.12E+00 3.50E+01 36.1 '9.95E'01 3.41E+01
99 38.9 '9.39E'01 3.54E+01 53.6 '1.13E+00 3.48E+01 35.9 '1.01E+00 3.40E+01
100 38.7 '9.53E'01 3.52E+01 53 '1.15E+00 3.47E+01 35.8 '1.02E+00 3.39E+01
101 38.4 '9.74E'01 3.51E+01 52.4 '1.17E+00 3.45E+01 35.7 '1.04E+00 3.37E+01
102 38.2 '9.88E'01 3.49E+01 51.9 '1.18E+00 3.44E+01 35.6 '1.06E+00 3.36E+01
103 37.9 '1.01E+00 3.48E+01 51.4 '1.21E+00 3.42E+01 35.5 '1.08E+00 3.35E+01
104 37.7 '1.02E+00 3.47E+01 50.9 '1.22E+00 3.41E+01 35.4 '1.10E+00 3.33E+01
105 37.5 '1.04E+00 3.45E+01 50.3 '1.24E+00 3.39E+01 35.2 '1.11E+00 3.32E+01
106 37.3 '1.05E+00 3.44E+01 49.8 '1.25E+00 3.38E+01 35.1 '1.13E+00 3.31E+01
107 37.1 '1.07E+00 3.42E+01 49.4 '1.27E+00 3.37E+01 35 '1.14E+00 3.30E+01
108 36.9 '1.09E+00 3.41E+01 48.9 '1.28E+00 3.35E+01 34.9 '1.16E+00 3.28E+01
109 36.7 '1.10E+00 3.40E+01 48.6 '1.30E+00 3.34E+01 34.8 '1.17E+00 3.27E+01
110 36.5 '1.12E+00 3.38E+01 48.3 '1.32E+00 3.33E+01 34.6 '1.19E+00 3.26E+01
111 36.4 '1.13E+00 3.37E+01 48.1 '1.32E+00 3.31E+01 34.5 '1.20E+00 3.25E+01
112 36.2 '1.14E+00 3.36E+01 47.8 '1.34E+00 3.30E+01 34.3 '1.22E+00 3.24E+01
113 36.1 '1.15E+00 3.34E+01 47.5 '1.35E+00 3.29E+01 34.2 '1.23E+00 3.23E+01
114 36 '1.16E+00 3.33E+01 47 '1.36E+00 3.27E+01 34 '1.23E+00 3.21E+01
115 35.8 '1.18E+00 3.32E+01 46.6 '1.38E+00 3.26E+01 33.9 '1.25E+00 3.20E+01
116 35.7 '1.18E+00 3.31E+01 46.2 '1.38E+00 3.25E+01 33.7 '1.26E+00 3.19E+01
117 35.5 '1.20E+00 3.29E+01 45.9 '1.40E+00 3.24E+01 33.5 '1.28E+00 3.18E+01
118 35.4 '1.21E+00 3.28E+01 45.6 '1.41E+00 3.23E+01 33.4 '1.29E+00 3.17E+01
119 35.3 '1.22E+00 3.27E+01 45.3 '1.42E+00 3.22E+01 33.3 '1.30E+00 3.16E+01
120 35.2 '1.23E+00 3.26E+01 45 '1.43E+00 3.20E+01 33.2 '1.31E+00 3.15E+01
121 35 '1.25E+00 3.25E+01 44.7 '1.45E+00 3.19E+01 33.1 '1.32E+00 3.14E+01
122 34.9 '1.26E+00 3.24E+01 44.4 '1.46E+00 3.18E+01 33 '1.33E+00 3.13E+01
123 34.8 '1.27E+00 3.22E+01 44.1 '1.47E+00 3.17E+01 32.9 '1.34E+00 3.12E+01
124 34.7 '1.28E+00 3.21E+01 43.9 '1.48E+00 3.16E+01 32.7 '1.35E+00 3.11E+01
125 34.6 '1.29E+00 3.20E+01 43.5 '1.49E+00 3.15E+01 32.7 '1.36E+00 3.10E+01
126 34.4 '1.30E+00 3.19E+01 43.4 '1.51E+00 3.14E+01 32.6 '1.38E+00 3.09E+01
127 34.3 '1.31E+00 3.18E+01 43.1 '1.52E+00 3.13E+01 32.5 '1.39E+00 3.08E+01
128 34.1 '1.33E+00 3.17E+01 42.9 '1.54E+00 3.12E+01 32.4 '1.41E+00 3.07E+01
129 34 '1.34E+00 3.16E+01 42.6 '1.55E+00 3.11E+01 32.3 '1.43E+00 3.07E+01
130 33.9 '1.35E+00 3.15E+01 42.3 '1.56E+00 3.10E+01 32.3 '1.44E+00 3.06E+01
131 33.8 '1.37E+00 3.14E+01 42 '1.57E+00 3.09E+01 32.2 '1.45E+00 3.05E+01
132 33.7 '1.38E+00 3.13E+01 41.8 '1.58E+00 3.08E+01 32.1 '1.46E+00 3.04E+01
133 33.6 '1.39E+00 3.12E+01 41.4 '1.59E+00 3.07E+01 32 '1.47E+00 3.03E+01
134 33.5 '1.40E+00 3.11E+01 41.2 '1.60E+00 3.06E+01 31.9 '1.48E+00 3.02E+01
135 33.3 '1.42E+00 3.10E+01 40.9 '1.62E+00 3.05E+01 31.9 '1.50E+00 3.01E+01
136 33.2 '1.43E+00 3.09E+01 40.6 '1.63E+00 3.04E+01 31.8 '1.51E+00 3.01E+01
137 33.1 '1.44E+00 3.08E+01 40.4 '1.65E+00 3.03E+01 31.7 '1.52E+00 3.00E+01
138 33 '1.45E+00 3.07E+01 40.1 '1.66E+00 3.03E+01 31.7 '1.54E+00 2.99E+01
139 32.9 '1.46E+00 3.06E+01 39.8 '1.67E+00 3.02E+01 31.6 '1.55E+00 2.98E+01
140 32.8 '1.48E+00 3.06E+01 39.6 '1.68E+00 3.01E+01 31.5 '1.56E+00 2.98E+01

14. 13