Temperature Transducers Lab Report

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University of Houston *

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3360

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Electrical Engineering

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Apr 3, 2024

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Calibration of Temperature Transducers Nguyen Bui Trung Nguyen MECE 3360 Date Conducted: 3/18/2024 Due Date: 3/29/2024 Submission Date: 3/19/2024 Abstract This lab introduces 3 temperature transducers which are the thermometer, thermocouple, and thermistor. Resistance, voltage, and temperature readings will be taken to obtain linear relationships between these devices with respect to a reference ice bath. Collected data then will be processed using a circuit equation and conversion tables in order to derive actual temperature measurements. By comparing the linear relationships between the transducers, individuals can determine the most accurate method for measuring temperature.

Objectives Learn the principles of operations and calibration techniques of the three transducers and understand the temperature versus time relationships. Introduction Temperature is crucial in engineering applications as it directly affects material properties, performance, and the behavior of various systems. In fields like mechanical, electrical, and chemical engineering, precise control and consideration of temperature are essential for ensuring the reliability, efficiency, and safety of processes and products. From determining the thermal expansion of materials to optimizing combustion processes in engines, understanding and managing temperature variations is fundamental for achieving desired outcomes in engineering endeavors. Procedures 1. Assemble the AD620 instrument amplifier that will be used for the thermocouple per the instruction. Connect output signals to the oscilloscope inputs (Channel 1 and Channel 2) and set the oscilloscope to measure the mean voltages. 2. Connect the thermocouple to the amplifier inputs according to the circuit diagram. Verify that the amplified output increases with the thermocouple’s temperature of the longer lead using the oscilloscope. If not, reverse the input connections (longer → shorter lead and vice versa) to the amplifier. 3. Prepare an ice bath and add water to it to ensure that there is no subcooled ice. Place all the sensors in the ice bath and take initial/0°C readings. 4. Fill a beaker three-fourth full, place it on the heater, and put a stirrer in to obtain a uniform temperature (do not stir too vigorously and be sure the heater is off). 5. Place all sensors in the beaker, except the thermocouple with the shorter lead that remains in the ice bath to serve as a reference point. Add some ice to the beaker to cool the water down to 10°C and then take the first reading. 6. Turn on the heater and keep stirring. Take a set of readings that include the RTD’s resistance, the thermometer’s temperature, Channel 1’s mV and Channel 2’s V at an interval of 5 °C (starting from 10 °C). Stop taking readings and turn off the heater at 50 °C (10 sets of readings in total).

Results Table 1. Thermometer's Temperature and RTD's Resistance Readings Thermometer [°C] RTD [Ω] RTD [°C] 0 100.08 0 10 103.775 10 15 106.212 16 20 108.021 21 25 110.788 28 30 111.956 31 35 113.821 36 40 115.635 40 45 117.639 45 50 119.897 51 Table 1 shows the collected data of the thermometer’s temperatures, the RTD’s resistances, and the converted RTD’s temperatures using the tables provided in the manual. The calibration equation obtained from Figure 1 is y = 0.9929x - 0.6024 and the R 2 value is 0.9968 . Figure 1. RTD vs. Thermometer Temperatures y = 0.9929x - 0.6024 R² = 0.9968 -10 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Thermometer [ ° C] RTD [ ° C] RTD T vs. Thermometer T

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Table 2. Channel 1's Voltages and RTD's Temperatures Channel 1 [mV] Channel 1 [mV, reduced by 500 times] Thermocouple [°C] RTD [°C] -16 -0.032 1 0 152 0.304 8 10 278 0.556 14 16 378 0.756 19 21 515 1.03 26 28 578 1.156 29 31 674 1.348 34 36 775.4 1.5508 39 40 891 1.782 44 45 1014 2.028 50 51 Table 2 shows the data of Channel 1’s voltages, the RTD’s converted temperatures, and the thermocouple’s converted temperatures using the tables provided in the manual. The calibration equation obtained from Figure 1 is y = 0.9868x - 1.0334 and the R 2 value is 0.9965 . Figure 2. RTD vs. Thermocouple Temperatures y = 0.9868x - 1.0334 R² = 0.9965 -10 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Thermocouple [ ° C] RTD [ ° C] RTD T vs. Thermocouple T

Table 3. Channel 2's Voltages and RTD's Temperatures Channel 2 [V] Thermistor [Ω] Thermistor [°C] RTD [°C] 9 15000 2 0 7.326 9546.520719 11 10 6.243 7129.15382 17 16 5.501 5791.135909 22 21 4.497 4281.633819 29 28 4.056 3706.140351 32 31 3.564 3116.474292 36 36 3.01 2510.425354 41 40 2.531 2029.833988 47 45 2.069 1600.030933 53 51 (1) Table 3 shows the data of Channel 2’s voltages, the RTD’s converted temperatures, the thermistor’s calculated resistances and converted temperatures using Equation (1) and the tables provided in the manual. The calibration equation obtained from Figure 1 is y = 1.0019x + 1.1476 and the R 2 value is 0.9985 . Figure 3. RTD vs. Thermistor Temperatures y = 1.0019x + 1.1476 R² = 0.9985 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Thermistor [ ° C] RTD [ ° C] RTD T vs. Thermistor T

Table 4. Calculated ln(R/R 0 ) and (T 0 /T) - 1 values Thermistor [Ω] Thermistor [°C] Thermistor [K] ln(R/R0) (T0/T) - 1 15000 2 275 0 0 9546.520719 11 284 -0.451873436 -0.032374481 7129.15382 17 290 -0.743857653 -0.053150366 5791.135909 22 295 -0.951721744 -0.067884276 4281.633819 29 32 -1.253715531 -0.089169125 3706.140351 32 305 -1.398059203 -0.099300612 3116.474292 36 309 -1.571347873 -0.111429763 2510.425354 41 314 -1.787597998 -0.12653034 2029.833988 47 320 -2.000096191 -0.141279215 1600.030933 53 326 -2.238027239 -0.157714881 Table 4 shows the calculated values of ln(R/R 0 ) and (T 0 /T) - 1 using the thermistor’s resistances and absolute temperatures. The calibration equation obtained from Figure 1 is y = 14.299x + 0.0048 and the R 2 value is 0.9998 . The closer the R 2 value is to 1, the better the model fits the data. Out of all three temperature plots for the three transducers, the plot of the thermistor has the highest R 2 value of 0.9985. The resolution of all three transducers is all ± 1°C. Conclusions The thermistor is the most accurate temperature measuring transducer among all three devices used in this experiment because it has the highest coefficient of determination, indicating a perfect linear relationship to the RTD’s temperature. Figure 4. ln(R/R 0 ) vs. (T 0 /T) - 1 y = 14.299x + 0.0048 R² = 0.9998 -2.5 -2 -1.5 -1 -0.5 0 0.5 -0.18 -0.16 -0.14 -0.12 -0.1 -0.08 -0.06 -0.04 -0.02 0 Ln(R/R0) (T 0 /T) - 1 Ln(R/R 0 ) vs. (T 0 /T) - 1

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