Exp 2 - Temp Measurement (1)

College of Engineering Chemical Engineering Department CME320: Chemical Engineering Laboratory I FALL 2017-2018

Experiment 2 Temperature Measurement

Group. 1/ Section. 51

Name

ID

Amal Radwan Jamal Eddin

1050893

Sara Allhalaq

1051713

Zaina AlDhaheri

1046702

Saniha Aysha Ajith

1051470

Instructor: Engr. Elron Gomes Experiment Date: Sunday, 24th of September 2017 Submission Date: Sunday, 24th of September 2017

Abstract Temperature measurement is a necessity in almost all of today’s fields and especially in areas of science and engineering. There are different devices for measuring the temperature and each is best applied in certain applications. Through this experiment, seven different temperature measurement devices were operated and compared with the help of a reference temperature sensor using a TD400 measurement and calibration apparatus. According to the results, it was seen that platinum resistance thermometer (PRT) varies linearly with temperature while the non-linearity of negative temperature coefficient (NTC) was proved. From the results, it is seen that PRT is the most accurate device for measuring temperature due to its lowest range of errors, which is 00.94% to 1.65%. The largest average errors occurring through the experiment were from the K type thermocouple which ranged from 23.34% to 81.32% followed by the J type thermocouple whose range of errors was from 23.45% to 93%. These errors are a result of several possible mistakes discussed in the report.

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Table of Contents Introduction ................................................................................................................................ 5 Theory ........................................................................................................................................ 5 Experimental Set-up................................................................................................................... 9 Procedure ................................................................................................................................. 14 Safety considerations............................................................................................................ 15 Data Collected .......................................................................................................................... 16 Results ...................................................................................................................................... 18 Sample Calculations................................................................................................................. 27 Discussion ................................................................................................................................ 29 Conclusion ............................................................................................................................... 31 References ................................................................................................................................ 34

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Table of Figures Figure 1 - PRT schematic diagram ............................................................................................ 6 Figure 2 - Infrared temperature sensor ………………………………………………………..6 Figure 3 - Semiconductor temperature sensor ........................................................................... 7 Figure 4 - Pyrometer .................................................................................................................. 8 Figure 5 - TD400 apparatus at ADU ……………………………...………………………….8 Figure 6 - Temperature measurement calibration apparatus (TD400).................................. 9 Figure 7 - Water heater tank ..…………………….…………………………………………..9 Figure 8 - Water draining tap/ valve ……………………………………….………………..10 Figure 9 - Reference Display (left) and millivoltmeter (right) ................................................ 10 Figure 10 - PRT and NTC thermistor sockets ......................................................................... 11 Figure 11 - Thermocouple J and K type sockets...................................................................... 11 Figure 12 - Platinum resistance thermometer (PRT) ............................................................... 12 Figure 13 - Image for NTC thermistor ..................................................................................... 12 Figure 14 - J and K type thermocouples .................................................................................. 13 Figure 15 - Schematic of J and K thermocouples ................................................................... 13 Figure 16 - Gas pressure thermometer………………………………………………………12 Figure 17 - Bimetallic thermometer………………………………………………………….13 Figure 18 - Liquid filled glass thermometer ............................................................................ 14 Figure 19 - Resistance Vs. Reference Temperature Plot for PRT ........................................... 19 Figure 20 - Resistance Vs Reference Temperature for NTC ................................................... 20 Figure 21 - Voltage Vs. Reference Temperature from J type Thermocouple ......................... 21 Figure 22 - Standard Voltage VS Measured Voltage for K type thermocouple ...................... 22 Figure 23 - K-Type Thermocouple Voltages Vs. References Temperature ............................ 22 Figure 24 - Indicated Temperature for gas thermometer ......................................................... 23 Figure 25 - Temperature Vs Number of Trials for gas thermometer ....................................... 24 Figure 26 - Indicated Vs Reference Temperature plot for Bi-Metallic Thermometer ............. 25 Figure 27 - Temperature Vs. Number of trials ........................................................................ 25 Figure 28 - Indicated Temperature Vs. Reference Temperature ............................................. 26 Figure 29 - Reference Temperature & Indicated Temperature Vs. Number of Trials ............ 27

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List of Tables Table 1 : Run I Data ................................................................................................................. 16 Table 2 : Run II Data ............................................................................................................... 17 Table 3 : PRT Results .............................................................................................................. 18 Table 4 : NTC Results.............................................................................................................. 19 Table 5 : J type thermocouple Results ..................................................................................... 20 Table 6 : K type Thermocouple Results .................................................................................. 21 Table 7 : Gas Thermometer Results......................................................................................... 23 Table 8 : Bi-metallic Thermometer.......................................................................................... 24 Table 9 : Liquid Red Spirit Thermometer Results ................................................................... 26

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Introduction Temperature is defined as the energy level of matter which can be evidenced by some change in that matter. Temperature sensors come in a so many different variety but have one thing in common - they all measure temperature by sensing some change in a physical characteristic [1]. All temperature sensing devices have their own advantages and disadvantages. The most important feature of the different types of temperature measurement devices is accuracy and linearity of measurement. In this experiment, seven different temperature measuring devices were used to compare and understand accurate temperature measurements. The seven devices used in the experiment are:       

Platinum resistance thermometer (PRT) Negative Coefficient thermostat (NTC) J type thermocouple K type thermocouple Gas pressure thermometer Liquid red spirit thermometer Bimetallic thermometer

The main objectives of this experiment are to learn how to operate and make connections for the platinum resistance thermometer (PRT), NTC Thermistor, thermocouples and thermometers. The other objective is to prove the linearity of the platinum resistance thermometer (PRT) and the non-linearity of the NTC Thermistor as well as compare the linearity and output signal levels of J and K type thermocouples.

Theory A platinum resistance thermometer (PRT) is a device which determines the temperature by measuring the electrical resistance of a section of pure platinum wire. This platinum wire is known as the temperature sensor. This device offers excellent combination of sensitivity, range and reproducibility which makes it one of the best temperature measuring devices. The reason why platinum wire is used is because it is a stable unreactive metal which can be drawn down to fine wires but is not too soft. Using very pure wires, thermometers can be made with closely similar resistance characteristics and achieve good reproducibility in use [2]. An increase in temperature will increase the resistance of the sensor. This proves the linearity of a PRT. The measurement is completed by applying a small measurement voltage and utilizing a bridge type circuit. The maximum range recommended for an industrial PRT is -200 to +650°C [3].

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Figure 1 - PRT schematic diagram

NTC Thermistors are non-linear resistors, which alter their resistance characteristics with temperature. The resistance of NTC will decrease as the temperature increases. One of the main ways to measure temperature using an NTC Thermistor is with a Wheatstone bridge. In addition, NTC Thermistors are frequently used to compensate for fluctuations in temperature in coils and solenoids [4]. It uses an electrical resistor made of a semiconductor material instead of a metal. Thermocouple is a sensor used to measure temperature. They consist of two wire legs made from different metals. The wires legs are welded together at one end, creating a junction. This junction is where the temperature is measured. When the junction experiences a change in temperature, a voltage is created. The voltage can then be interpreted using thermocouple reference tables to calculate the temperature. There are many types of thermocouples, each with its own unique characteristics in terms of temperature range, durability, vibration resistance, chemical resistance, and application compatibility. Type J, K, T, & E are “Base Metal” thermocouples, the most common types of thermocouples. Type R, S, and B thermocouples are “Noble Metal” thermocouples, which are used in high temperature applications. 

The type J is very common and has a small temperature range and a shorter lifespan at higher temperatures than the Type K. The temperature range for this type is usually -210 to 760C. and standard accuracy is usually +/- 2.2C or +/- .75% [5].



The type K made of nickel and chromium or nickel and aluminum is the most common type of thermocouple. It’s inexpensive, accurate, reliable, and has a wide temperature range. Its temperature range is usually –270 to 1260C and it has a standard accuracy of +/- 2.2C or +/- .75% [5]

A thermometer is a device that records the temperature of a substance relative to some agreed upon standard. Thermometers use changes in the physical or electronic properties of the device to detect temperature variations. For example, the most common thermometer consists of a liquid sealed in a narrow tube, with a calibrated scale attached. The liquid, typically mercury or alcohol, has a high coefficient of thermal expansion, that

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is to say the volume changes significantly with changes in temperature. Combined with the narrowness of the tube, this means that the height of the column of liquid changes significantly with small temperature variations [6]. In this experiment, three types of thermometers were used to measure temperature:  Gas pressure thermometer: Measures the pressure exerted by a definite amount of gas enclosed in a constant volume. The gas is usually hydrogen or helium is enclosed in a glass bulb connected to a mercury manometer [7].  Liquid red spirit thermometer: The alcohol/ spirit thermometer is an alternative to the mercury-in-glass thermometer but has similar functions. The contents of an alcohol thermometer are less toxic and will evaporate away fairly quickly. The ethanol version is the most widely used due to the low cost and relatively low hazard posed by the liquid in case of breakage [8].  Bimetallic thermometer: Bimetallic thermometers are made up of two metallic strips formed by joining two different metals having different thermal expansion coefficients. Basically, bimetallic strip is a mechanical element which can sense temperature and transform it into a mechanical displacement [9]. In addition to the mentioned above temperature devices, various other devices can be used which work on different principles. A few of these devices are mentioned below: 1. Infrared temperature measurement devices: Infrared sensors are non-contacting devices which infer temperature by measuring the thermal radiation emitted by a material. These sensors are classified into two types such as thermal infrared sensors and quantum infrared sensors [10]. 2. Semiconductor based sensors: A semiconductor-based temperature sensor is placed on integrated circuits (ICs). These sensors are effectively two identical diodes with temperature-sensitive voltage vs current characteristics that can be used to monitor changes in temperature. They offer a linear response but have the lowest accuracy of the basic sensor types at 1 to 5 °C [11]. 3. Pyrometer: A pyrometer is a type of remote-sensing thermometer used to measure the temperature of a surface. In the modern usage, it is a device that from a distance determines the temperature of a surface from the spectrum of the thermal radiation it emits, a process known as pyrometry and sometimes radiometry [12].

Figure 2 - infrared temperature sensor

Figure 3 - Semiconductor temperature sensor

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Figure 4 - Pyrometer

Temperature measurement in chemical engineering industry encompasses a wide variety of needs and applications. To meet this wide array of needs, the process controls industry has developed a large number of sensors and devices to handle this demand. Temperature is a very critical and widely measured variable for most chemical engineers in almost all fields. This can range from the simple monitoring of the water temperature of a storage tank or as complex as the temperature of a fluids in a heat exchanger [13]. For the completion of the experiment and to get accurate results, the following equations are used for calculations:  Resistance is calculated using Ohm’s law: R =

where, R = resistance (Ω)

V I

[Equation 1]

V = voltage (V) I = current (A)  In many cases, interpolation is needed to find the standard resistance or voltage: X1

Y1

X2

Y2

X3

Y3

−

Y =

−

−

+Y

[Equation 2]

 To find the deviation of calculated experimental values from standard ones Deviation = |Standard value – Experimental value| [Equation 3]

 Percentage error =

|D viati Sta

ar

|

×

[Equation 4]

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Experimental Set-up The overall appearance of the temperature measurement and calibration apparatus, TD400, is its metal frame and contains an icebox, water heater tank, low voltage connections, and a digital display. The low voltage electrical connections are made for the low voltage measurement devices [15]. These devices include: the platinum resistance thermometer (PRT), negative temperature coefficient (NTC) thermistor, J type and K type thermocouples. Other devices that are used in this apparatus but are not connected to the low voltage connections are: liquid filled thermometers, gas and bi-metallic thermometers. This apparatus could be placed anywhere on a desk near a draining sink or a bench top, as it is an easy equipment to place anywhere desired. It can be connected to a software program called the TecQuipment’s Versatile Data Acquisition System (VDAS®) [14]. The overall equipment is shown in Figure 6. Figure 5 shows the apparatus that was used during the experiment at Abu Dhabi University Chemical Engineering Laboratory.

Figure 5 - TD400 measuring and calibration device

Figure 6 – TD400 apparatus at ADU

The equipment has a built-in temperature and pressure sensor. The temperature sensor works accurately to show accurate temperature reference. The pressure sensor shows the local (barometric) pressure. The display also shows the local boiling point of water based on the barometric pressure [14]. For safety, the water heater has a water level sensor/float switch and a cut-out switch to switch off the heater when the water level is low [15]. The water heater tank has a lid with holes to hold the measurement tools during the experiments. It has a drain tap (shown in Figure 8) that can be connected to a container, sink, or any water drain. This helps in easily change water during runs in an experiment, save time and be safe [14]. At the front of the heater tank, there is a small temperature scale to show the temperature of the water as it is increasing and/or decreasing and is just for reference [14]

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Figure 7 - Water heater tank

Figure 8 - Water draining tap/ valve

The icebox is also safe by being insulated thermally. The insulation is made to hold the ice and slow the melting process during experiments. There is a container-like in the icebox that can be removed to pour out the ice or the ice water during and after experiments. Like the heater tank, it has a lid with holes to hold the devices during the experiments. The digital displays include the Reference Display and the Millivoltmeter (shown in Figure 9) each with their own characteristics displayed. The reference display shows, the accurate reference temperature given by the reference sensor, the barometric pressure, the boiling point temperature of water based on the barometric pressure. The millivoltmeter shows four voltages from each of the four input and output sockets on the sides of the display [15].

Figure 9 - Reference Display (left) and millivoltmeter (right)

The low voltage connections have two main sockets: The PRT and NTC Thermistor sockets and the Thermocouple J and K type sockets. The PRT and NTC thermistor sockets (shown in Figure 10) have a constant current source, constant voltage source, fixed resistances with high accuracy in a circuit that stimulates PRT at 0°C (100 Ohm) and its connection wires (R1, R2, R3, R4), and fixed resistances with high accuracy in a Wheatstone Bridge Circuit of three 100-R-resistors to match the 100-Oh, resistance of a PT100 at 0°C [15].

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Figure 10 - PRT and NTC thermistor sockets

The J and K type thermocouple sockets (shown in Figure 11) have a voltage amplifier, which increases the output voltage from the thermocouples that are relatively small to a suitable level for the experiment. The sockets also have four spare junction sockets that are not electrically connected to anything, which can be used during experiments to keep tidy wiring. Finally, these sockets have three fixed resistors, which simulate extra resistances in the circuits used with measuring devices. [15].

Figure 11 - Thermocouple J and K type sockets

Temperature measurement devices 1. Resistance thermometers The types of resistance thermometers are sometimes called PRT’s and RTD’s. They refer to Platinum Resistance Thermometer and Resistance Temperature Detectors, respectively. They measure temperature through change in electrical resistance of a length of wire. Platinum is used because it gives off linearity for resistance change versus temperature and is stable. It has a very wide operating temperature range, between -200 to +650°C. Increase in temperature will increase the resistance to the sensor. [16]. Figure 12 shows how a PRT looks while Figure 1 gives the schematic makeup of a PRT.

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Figure 12 - Platinum resistance thermometer (PRT)

2. Negative temperature coefficient (NTC) thermistor Thermistors are temperature-sensing elements and are made up from semiconductor material. Using small and measured direct current that passes through the thermistor, resistance is measured, which measures the voltage drop that occurs. NTC thermistors have a non-linearity characteristic of resistance versus temperature. This means, as temperature increases, resistance decreases. [17]. It can only be used if PRT is not being used on the TD400 as they use the same connections. Check figure 13.

Figure 13 - Image for NTC thermistor

3. J and K type thermocouples Thermocouples of two types, two K type and one J type (shown in Figure 14), when they’re put in an electrical or electronic circuit, they convert the small potential difference into voltage or current of calibrated value [15]. The J type thermocouple has white and black insulation, whereas, the K type thermocouple has green and white insulation. (Figure 15). The J and K type thermometers use the same connections to use the thermocouple it must be one at a time.

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Figure 14 - J and K type thermocouples

Figure 15 - Schematic of J and K thermocouples

4. Gas and Bi-metallic thermometers The gas and Bi-metallic thermometers have a mechanical dial calibrated to show temperature. The gas thermometer (shown in Figure 16) works when the gas expands due to temperature increase, so the pressure increases and pushes against the mechanical calibrated dial. The bi-metal thermometer (shown in Figure 17) has two metal strips held together to make one thick strip, which is a composite of the two. As the temperature rises, one metal expands and the other composite bends, which pushed the mechanical calibrated, dial. [15].

Figure 16 - Gas pressure thermometer

Figure 17 - Bimetallic thermometer

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5. Liquid filled glass thermometers The difference between the two thermometers is that one used low toxicity liquid while the other uses the red spirit. Opposite to the gas and bi-metal thermometers, the liquid filled glass thermometers work on the process of liquid volume expansion, which is due to rise in temperature. As liquid expands, it moves up or down a capillary tube behind a scale. [15]. Figure 18 shows two liquid thermometers.

Figure 18 - Liquid filled glass thermometer

Procedure Note: The experiment was made in two runs. Run 1 measured with the PRT, J-type thermocouple, and the bi-metallic thermometer. In contrast, Run 2 was measured with NTC thermistor, K-type thermocouple, gas thermometer and red spirit (liquid-filled) thermometer. Experiment Start-up 1. 2. 3. 4. 5.

Close the drain tap behind the heater tank and switch off electrical supply. Remove the lid of the heater tank and add distilled water until its almost half full. Cover the tank with the lid. Remove the lid of the icebox, add ice and put back the lid. Assure that heater switch if turned off and switch on the electrical supply.

Run 1 1. 2. 3. 4.

Connect the reference sensor to the socket it belongs to. Connect the PRT to the millivoltmeter and the constant current source. Connect the J-type thermocouple to the millivoltmeter and the amplifier. Place the reference sample along with the PRT, J-type thermocouple, and the bimetallic thermometer into the icebox, wait for the reference temperature to stabilize at 0°C and record the other readings.

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5. Place the reference sample along with the PRT, J-type thermocouple, and the bimetallic thermometer in the heater tank, switch on the heater and record the reference temperature. 6. With 10°C-intervals, record the readings of the millivoltmeter and the calibration scale of the bimetallic thermometer. Note: when reading the bi-metallic thermometer scale, make sure to tap on the calibration scale to avoid extreme errors made by friction. 7. When temperature equals 100°C, stop the experiment and switch off the heater. 8. Remove the lid of the heater tank and wait for the water in the heater tank to cool to 70°C (add ice if necessary). 9. Drain the water. (Water needs to be changed between runs). Run 2 1. 2. 3. 4. 5.

Re-add distilled water in the water heater tank till it’s almost half full. Connect the reference sensor to the socket it belongs to. Connect the NTC thermistor to the millivoltmeter and the constant current source. Connect the K-type thermocouple to the millivoltmeter and the amplifier. Place the reference sample along with the NTC thermistor, K type thermocouple, gas thermometer and red-spirit-glass-thermometer into the icebox, wait for the reference temperature to stabilize at 0°C and record the other readings. 6. Place the reference sample along with the NTC thermistor, K type thermocouple, gas thermometer and red-spirit-glass-thermometer in the heater tank, switch on the heater and record the reference temperature. 7. With 10°C-intervals, record the readings of the millivoltmeter, the red spirit glassthermometer and the calibration scale of the gas thermometer. Note: when reading the gas thermometer scale, make sure to tap on the calibration scale to avoid extreme errors made by friction. 8. When temperature equals 100°C, stop the experiment and switch off the heater.

Experiment Shut-down 1. Remove the lid of the water heater tank, and wait till temperature decreases to 70°C. To fasten the process, add ice to the tank, if necessary. 2. Open the drain valve and empty the tank. 3. Turn off the main power supply. Safety considerations During practical work proper supervision is required. All personnel should be aware of the dangers that might occur when dealing with lab materials, high pressure and high temperature conditions. People performing this experiment should wear appropriate PPEs including: lab coats, safety goggles, hard covered shoes, and high-impact gloves. In addition, Students can

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perform the experiment alone if they have competent supervision by an instructor/engineer. Some physical, chemical, and mechanical hazards that may potentially arise while performing the experiment are mentioned below:   

Mechanical: be aware of hot materials (heater tank) as it can burn the skin. Electrical: be gentle when using/pouring/moving water when the electrical supply is on as electrical disasters can occur if water falls on any electric supply. Physical: safely and careful deal with the hot tank and the ice as both can cause physical damage to the skin.

Data Collected To perform this experiment, seven devices were used in two different runs at different temperatures. The below tables show the collected data of both the runs.

Table 1 : Run 1 data

Reference Temperature (oC)

Measured voltage PRT (mV)

Measured

Temperature

voltage J – type thermocouple (mV)

reading Bi- metallic thermometer (oC)

0

101.5

24.6

-0.1

22.4

110.3

1.6

21.8

32

113.3

-6.8

37.7

42

117.8

-18

39.6

52

121.5

-28.2

49.1

62

125.2

-39

60.6

72

129.2

-49.9

70.2

82

132.9

-60.5

80.1

92

139.7

-72.3

90.5

98

139.7

-79

97.8

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Table 2 : Run II Data

Reference Temperature (oC)

Measured voltage NTC Thermistor (mV)

Measured voltage K – type thermocouple (mV)

Temperature reading gas pressure thermometer (oC)

0

263.7

-18.1

0.38

27.4

97.2

4.1

27.8

37

69.7

9.4

37.7

47

51.3

17.1

47.7

57

38.2

25.1

56.4

67

27.8

35.6

68.2

77

21.7

43.7

76.9

87

16.8

51.2

88

97

13.1

60.9

98.5

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Results For each of the seven devices, the deviation and error were calculated from the standard values provided in Appendix A. A plot was then plotted for each of the device to show the deviation and comparison with reference temperature

1. Results and calculations of Platinum Resistance Thermometer are presented in Table3. Table 3 : PRT Results

Reference Measured Temperature Voltage (mV) (°C)

Calculated Resistance (Ω)

Standard Resistance (Ω)

Deviation (Ω)

Error (%)

0

101.5

101.5

100

-1.5

1.5

22.4

110.3

110.3

108.73

-1.574

1.45

32

113.3

113.3

112.06

-1.24

1.11

42

117.8

117.8

116.31

-1.49

1.28

52

121.5

121.5

120.17

-1.33

1.11

62

125.2

125.2

124.01

-1.19

0.96

72

129.2

129.2

127.84

-1.36

1.06

82

132.9

132.9

131.66

-1.24

0.94

92

137.7

137.7

135.47

-2.23

1.65

98

139.7

139.7

137.75

-1.95

1.42

Range of errors: 0.94% to 1.65%

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Resistance Vs. Reference Temperature Plot for PRT Resistance Ω

150 140 130

Calculated Resistance

120

Standard Resistance

110

Linear (Calculated Resistance)

100

Linear (Standard Resistance) 0

22,4 32

42

52

62

72

82

92

98

Reference Temperature (°C)

Figure 19 - Resistance Vs. Reference Temperature Plot for PRT

2. Results and calculations of Negative Coefficient Thermostat is presented in Table 4 Table 4 : NTC Results

Reference Temperature (°C) 0

Measured Voltage (mV)

Calculated Resistance (Ω)

Deviation (Ω)

Error (%)

263.7

Standard Resistance (Ω) 261

263.7

-2.7

1.03

27.4

97.2

97.2

92.41

-4.7936

5.19

37

69.7

69.7

66.76

-2.94

4.40

47

51.3

51.3

48.47

-2.832

5.84

57

38.2

38.2

35.75

-2.448

6.85

67

27.8

27.8

26.88

-0.922

3.43

77

21.7

21.7

20.51

-1.194

5.82

87

16.8

16.8

15.87

-0.926

5.83

97

13.1

13.1

12.44

-0.664

5.34

Range of errors: 1.03% to 6.85%

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Resistance Vs Reference Temperature 300

Resistance Ω

250 200 150 100 50 0 0

20

40

60

80

100

120

Reference Temperature (°C) Calculated Resistance

Standard Resistance

Figure 20 - Resistance Vs Reference Temperature for NTC

3. Results and calculations of J type thermocouple are presented in Table 5 Table 5 : J type thermocouple Results Reference Temperature (℃)

Actual Voltage (𝑚𝑉)

Standard Voltage (𝑚𝑉)

Deviation (𝑚𝑉)

Error (%)

0

Measured Voltage (J) type thermocouple) (mV) -24.6

1230

0

-1230

-

22.4

-1.6

80

1142.8

1062.8

92.99

32

6.8

340

1641

1301

79.28

42

18

900

2164

1264

58.41

52

28.2

1410

2691

1281

47.60

62

39

1950

3222

1272

39.478

72

49.9

2495

3757

1262

33.59

82

60.5

3025

4294

1269

29.55

92

72.3

3615

4835

1220

25.23

98

79

3950

5160

1210

23.45

Range of errors: 23.45% to 92.99%

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Voltage Vs. Reference Temperature from J type Thermocouple 6000 5000

Achsentitel

4000 3000 2000

Actual Voltage

1000

Standard Voltage

0 0

20

40

60

80

100

120

-1000 -2000

Achsentitel

Figure 21 - Voltage Vs. Reference Temperature from J type Thermocouple

4. Results and calculations of K type thermocouple are presented in Table 6 Table 6 : K type Thermocouple Results Reference Temperature (°C)

Measured voltage (mV)

Actual Measured Voltage

Standard

Deviation

Voltage

(𝜇 V)

(𝜇V)

(𝜇V)

Error (%)

0

-18.1

-905

0

905

-

27.4

4.1

205

1097.4

892.4

81.32

37

9.4

470

1489

1019

68.44

47

17.1

855

1899

1044

54.97

57

25.1

1255

2312

1057

45.71

67

35.6

1780

2727

947

34.73

77

43.7

2185

3142

957

30.46

87

51.2

2560

3557

997

28.03

97

60.9

3045

3972

927

23.34

Range of errors: 23.34% to 81.32%

21

Measured Voltage(𝜇V)

Standard Voltage VS Measured Voltage 4095 3895 3695 3495 3295 3095 2895 2695 2495 2295 2095 1895 1695 1495 1295 1095 895 695 495 295 95 -105 -100 100 300 500 700 900 1100 1300 1500 1700 1900 2100 2300 2500 2700 2900 3100 3300 3500 3700 3900 4100 -305 -505 -705 -905 Standard Voltage (𝜇V)

Figure 22 - Standard Voltage VS Measured Voltage for K type thermocouple

References Temperature against K-Type thermocouple Voltages Voltages(𝜇𝑉)

6000 4000 2000 0 -2000 0

20

40

60

80

100

120

Reference Temperature(°C ) Actual Measured Voltage

Standard Voltage

Figure 23 - K-Type Thermocouple Voltages Vs. References Temperature

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5. Results and calculations of gas pressure thermometer are presented in Table 7 Table 7 : Gas Thermometer Results

Reference Temperature (°C)

Indicated Temperature (°C)

Deviation (°C)

Error (%)

0

0.38

0.38

-

27.4

27.8

0.4

1.46

37

37.7

0.7

1.89

47

47.7

0.7

1.49

57

56.4

-0.6

1.05

67

68.2

1.2

1.79

77

76.9

-0.1

0.13

87

88

1

1.15

97

98.5

1.5

1.54 Range of errors: 0.13% to 1.89%

Indicated Temperature (°C) Reference Temperature (°C)

120 100 80 60 40 20 0 0

20

40

60

80

100

120

Indicated Temperature (°C)

Figure 24 - Indicated Temperature for gas thermometer

23

Temperature Vs. Number of Trials Temperature (°C)

120 100 80 60 40 20 0 0

1

2

3

4

5

6

7

8

9

10

Number of Trials Reference Temperature

Inicated Temperature

Figure 25 - Temperature Vs Number of Trials for gas thermometer

6. Results and calculations of bimetallic thermometer are presented in Table 8 Table 8 : Bi-metallic Thermometer Results

Reference Temperature (°C)

Indicated Temperature (°C)

Deviation (°C)

Error (%)

0

-0.1

-0.1

22.4

21.8

-0.6

2.68

32

38.2

6.2

19.37

42

39.6

-2.4

5.71

52

49.1

-2.9

5.57

62

60.6

-1.4

2.26

72

70.2

-1.8

2.5

82

80.1

-1.9

2.31

92

90.5

-1.5

1.63

98

97.8

-0.2

0.20 Range of errors: 0.20% to 19.37%

24

140 120 100 80 60 40 20 0 -20

0

22,4

32

42

52

62

72

82

Reference Temperature (°C)

92

98

Figure 26 - Indicated Vs Reference Temperature plot for Bi-Metallic Thermometer

Temperature Vs. Number of trials 120 100

Temperature (°C)

Indicated Temperature (°C)

Indicated Vs Reference Temperature plot for Bi-Metallic Thermometer

80 60 40 20 0 -20

1

2

3

4

5

6

7

8

9

10

Number of trials

Figure 27 - Temperature Vs. Number of trials

25

7. Results and calculations of liquid red spirit thermometer are presented in Table 9 Table 9 : Liquid Red Spirit Thermometer Results Reference Temperature (°C)

Indicated Temperature

Deviation

Error (%)

(°C)

(°C)

0

0.05

-0.05

0

27.4

27.5

-0.1

0.36

37

37

0

0

47

47

0

0

57

57.1

-0.1

0.17

67

68.8

-1.8

2.69

77

79

-2

2.59

87

90

-3

3.44

97

101

-4

4.12 Range of errors: 0% to 4.12%

indicated Temperature (°C )

Reference Temperature vs Red Spirit Indicated Temperature 120 100 80 60 40 20 0 0

20

40

60

80

100

120

Reference Temperature (°C )

Figure 28 – Indicated Temperature Vs. Reference Temperature

26

Reference Temperature&Red Spirit Indicated Temperature Temperature (°C )

120 100 80 60 40 20 0 0

1

2

3

4

5

6

7

8

9

10

Number of Trials Reference Temperature

Indicated Temperature

Figure 29 - Reference Temperature & Indicated Temperature Vs. Number of Trials

Sample Calculations This section shows detailed mathematical calculations for finding the data required for different measurement devices at reference temperature of 87 °C. For PRT and NTC Thermistor data, a sample calculation of NTC thermistor only is shown since NTC thermistor works in a similar way and same data are required to be calculated. The data required are: experimental resistance, standard resistance, and resistance percentage error. Calculated Resistance In order to find calculate resistance at 87 °C, the collected voltage values and constant supplied current (1 mA) can be applied in Ohm’s law. At 87 °C, measured voltage is found to be V Ohm's Law → R = I =

.

𝑉

𝐴

=

.

𝑉

𝐴

. 𝑚𝑉 on the Millivoltmeter screen

=

. Ω

Standard Resistance Table.1A in Appendix A shows the standard resistance of NTC thermistor at different temperatures. Since Tref = 87 °C is located between 85 °C and 90 °C, interpolation is preferable to find the accurate standard resistance. −

−

=

−

−



Percentage Error

.

−

−

.

.

Percentage Error % = |

= 𝑎

−

−

𝐷

𝑎

 R= 15.874 Ω

𝑖𝑎 𝑖

𝑖 𝑎

|×

%

Deviation Ω = Standard Resistance − Calculated Resistance 27

= 15.874 Ω -

. Ω = -0.926 Ω

Percentage Error %

=|

− .

.

Ω

|×

%=

.

%

For K & J type thermocouples, mathematical calculations for the required data is shown on K type thermocouple as both work on the same principle of potential difference across two different metals subject to a heat gradient. Hence, same data are required to be calculated which are: actual measured voltage, standard voltage, and voltage percentage error. Actual measured Voltage Thermocouples are connected through an amplifier which amplifies the small voltage from the thermocouple by 20 to make it suitable for the millivoltmeter. In order to find the actual measured voltage millivoltmeter readings are divided by 20. The voltage recorded at Tref 87 °C is 4.8 mV 

. ∗

= 240 𝜇V

Standard voltage From Table.2A in Appendix A, which shows the standard voltages at different temperatures, the standard voltage at 87 °C is 3557 𝜇V Percentage Error

Percentage Error % = |

𝑎

𝐷

𝑎

𝑖𝑎 𝑖 𝑉

𝑎

|×

%

Deviation μV = Standard voltage − Actual measured voltage = 3557 𝜇V-240 𝜇V= 3317 𝜇V

Percentage Error % = |

|×

%=

.

%

Thermometers are manufactured in a way temperature can be measured directly from a scale on the equipment. A sample of calculation for red spirit thermometer data is shown below. These data are: indicated temperature and temperature percentage error. Indicated temperature At reference temperature of 87 °C, the liquid in red spirit thermometer rises to reach a temperature of on the calibrated scale 90 °C

Percentage Error Percentage Error % = |

𝐷

𝑖𝑎 𝑖

𝑎

|×

%

28

Deviation °C = Reference Temperature − Measured Temperature = 87 °C-90 °C= -3 °C

Percentage Error % = |

−

|×

%= .

%

Discussion Through the temperature measuring experiment, knowledge of using different types of temperature measuring devices is gained. From the found results, the accuracy and the linearity of the measurements, which are the most important features, are compared. The instruments worked with are: platinum resistance thermometer (PRT), negative temperature coefficient (NTC) thermistor, K and J types thermocouples, gas and bi-metallic thermometers, and liquid filled glass thermometer. The results found, the comparison considered and the errors are discussed through the report. The first device used was the PRT, with a voltage reading in millivoltage. The PRT was equipped in the first run. Given that the constant current was set as 1 milliampere, the resistance was calculated using Ohm’s law in order to understand the relationship between the temperature and the resistance. The plotted graphs seen in Figure 19 shows the increase in the resistance due to the increase in temperature. As the temperature rises, the resistance of the wire increases increasing the voltage drop and eventually the resistance. The prediction of the relationship was reached from Ohm’s law ( 𝑅 =

𝑉 𝐼

) where it can be seen that R and V are

directly proportional as I is constant. Through graphing the calculated resistance and the standard resistance versus the temperature, the deviation of the graphs clearly represents the linearity of the two and the error present between them. The range of percentage error of the data was 0.94% to 1.65%, which is acceptable. This might have occurred due to several points to be discussed later in this report. NTC thermistor takes its name from the negative temperature coefficient of resistance. NTC thermistor was used in the second run. Similar to PRT, constant current was used as 1 milliampere and the resistance was calculated using the Ohm’s law. However, since NTC thermistor comprises of a semiconductor material, the resistance of the material decreases with the increase of temperature. The found data supports the prediction as can be seen in Figure 20. The graph also shows the non-linearity property of NTC thermistor. Through graphing both calculated and standard values, the error present in the experiment can be seen clearly. The error range in this case is 1.03% to 6.85%. Also, K and J type thermocouples were used through the experiment. Since both thermocouples are connected through the same port, the first run included the J type and the second one included the K type. The data was collected for each and calculations done. At first, the voltage was converted to the actual value in microvolts. Then, the standard voltages at the reference temperature values were found. Through these data, the graph of the voltage versus reference temperature was created. From the graphs in Figure 23 & Figure 21, the 29

linearity of the relationship can be clearly seen. Both K and J types have similar graphs. However, an error can be seen in the both types thermocouple, which reached a range of 23.34% to 81.32% for the K type and 23.45% to 92.99% for the J type thermocouple. The deviation is clearly present in the graphs and may be due to touching the tank walls, or wrong wires connections missed. The next device is the gas thermometer which was used in the second run. The gas thermometer showed in Table 7 shows great results compared to the reference temperature with a range of error of 0.13% to 1.89%. From the graph in Figure 24, the straight line shows the accuracy of the values from the gas thermometer. It shows the reference and indicated temperatures over the different trials and as clear, both line overlap one another showing the perfect results found. A very slight percentage error can also be seen and is a result of several mistakes. These errors will be discussed by the end of the discussion. Similar to the gas thermometer, the bi-metallic thermometer was used to measure the temperature in the first run. The temperature values found compared to the reference temperature were almost accurate but with a higher percentage error of that of the gas thermometer. The range of percentage error was found to be 0.20% to 19.37%. The errors occurring while measuring with the bi-metallic can be similar to those of the gas thermometer and will be discussed. Figure 26 & 27 show the graphs and how the values are close to those of the reference. The slight error can also be seen in the figures as the line deviate from the standard at the beginning. The mistakes predicted will be discussed later as they may be shared with the other devices. The last device, to measure the temperature, was the liquid filled glass thermometer used in the second run. It showed a high accuracy from the results found with a range of percentage error of 0% to 4.12%. Figure 28 & 29 shows how the values are compared to the reference each in a different way. From the figures, the accuracy of the device shows as the numbers are close to the reference and the curves overlap one another in Figure 29. The errors still occur of course and are explained below in the discussion. Comparing the instruments results with one another, the accuracy can be compared through the graphs found in the results. The least percentage error comes from PRT with least of 0% While the highest percentage error is found from K type thermometer with upper range of 92.99%. As mentioned before, the results include errors; therefore, the conclusion about which is most accurate is not final. The experiment also shows the operating difficulty of each instrument. The liquid glass filled thermometer is considered easiest to operate and the difficulty increase. Moreover, the similarities of the devices can be seen as well while comparing them including how they operate, the main concept behind the measurement, and the relations between results and actual values. Away from the perfection of the theory, the actual work includes a various amount of errors in any experiment. Temperature measurement is no exception. Each of the data collected from the different devices included errors that are similar or specific. All these devices share

30

the errors occurring due to getting the values at the exact reference temperature, and the not letting the device touch the sides of bottom of the tank. In addition, devices that required visual observation such as the gas, bi-metallic, and liquid filled glass thermometers, include the error of parallax. Moreover, the friction in the gas or bi-metallic thermometer which is removed by tapping the glass is also a source of error. In addition, wires used for connections can be the cause of errors. In the end, all the used instruments have a percentage error depending on the instrumentation finite precision. In terms of industrial importance of temperature measurement, it has an effect and usage in almost every factory and industry in today’s world. The process and product temperature is an important physical indicator for manufacturing processes and ensures a high-quality level of the production. It is of utmost importance in industries such as medical, semiconductor, solar, plastics, automotive and 3D laser scanning. It is also important in fire prevention and maintenance [18].

Conclusion In conclusion, the objectives were reached through the experiment and the different temperature measuring instruments were compared. Measuring tools used included platinum resistance thermometer (PRT), negative temperature coefficient (NTC) thermistor, K and J types thermocouples, gas and bi-metallic thermometers, and liquid filled glass thermometer. Through the report, a full understanding of how to operate these instruments and how to get the desired data was achieved. The results were interpreted, understood, and compared through the discussion. The report reached results which include the linearity of all instruments except for NTC, and the accuracy of PRT above all the other instruments. Furthermore, the success of the experiment relies on the elimination of the errors explained above. In addition, one of the ways to improve the results would be to use very cold water in the heater before starting. Another way is to take accurate readings from the temperature devices at the exact reference temperature.

31

Appendix Table.1A: Standards for PRT– Resistance for Temperature

Table.2A: Standards for NTC thermistor – Resistance for Temperature

32

Table.3A: Standards for J Type thermocouple

Table.4A: Standards for K Type thermocouple

33

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