Temperature Measuring Devices
Part
Liquid Filled Glass
Thermometers
Details
Sealed Glass Thermometers - Immersion Depth 76 mm
1 x Spirit Filled, Range: -10°C to 110°C
1 x Low toxicity liquid, Range: -10°C to 260°C
Bi-metal Thermometer Stainless steel shaft with mechanical gauge
Bi-metal system
Range: 0 to 100°C
Indicator Accuracy: 1.5% of scale
Gas (Vapour Pressure)
Thermometer
Stainless steel shaft with mechanical gauge
Inert gas system
Range: 0 to 100°C
Indicator Accuracy: 1% of scale
NTC Thermistor
Negative Temperature Coefficient
100 Ohm at 25°C
Tolerance: +/- 5%
Reference Sensor
and
Resistance
Temperature Detector
(RTD)
Platinum Resistance Thermometers (PRTs), type PT100 (platinum
- 100  at 0°C)
Normal Temperature range: -50°C to 250°C
Class A - High Accuracy
100  +/- 0.06  at 0°C.
Thermocouples
2 x K type - Nickel-Chrome, Nickel Aluminium
IEC Colour codes:
Green wire - Positive (+)
White wire - Negative (-)
Normal Temperature range: 0°C to 1100°C
Approximate Maximum Temperature range: -200°C to 1350°C
Accuracy +/- 1°C
1 x J type - Iron, Copper-Nickel
IEC Colour codes:
Black wire - Positive (+)
White wire - Negative (-)
Normal Temperature range: 0°C to 700°C
Approximate Maximum Temperature range: -40°C to 750°C
Accuracy +/- 1°C
Infrared Thermometer
Hand-held, battery powered.
Approximately 0.25 kg
NTC Thermistor - Standards
NOTE
Nominal resistance accuracy for the NTC Thermistor is +/- 5%.
°C

°C

0
261.0
55
37.82
5
212.6
60
32.64
10
174.4
65
28.33
15
144.2
70
24.70
20
119.9
75
21.57
25
100.0
80
18.91
30
84.18
85
16.65
35
71.08
90
14.71
40
60.32
95
13.02
45
51.42
100
11.56
50
44.04
Table 2 NTC Thermistor - Resistance For Temperatures
K Type Thermocouple Standards
°C
V
°C
V
°C
V
°C
V
°C
V
0
0
1
39
21
838
41
1653
61
2478
81
3308
2
79
22
879
42
1694
62
2519
82
3350
3
119
23
919
43
1735
63
2561
83
3391
4
158
24
960
44
1776
64
2602
84
3433
5
198
25
1000
45
1817
65
2644
85
3474
6
238
26
1041
46
1858
66
2685
86
3516
7
277
27
1081
47
1899
67
2727
87
3557
8
317
28
1122
48
1941
68
2768
88
3599
9
357
29
1163
49
1982
69
2810
89
3640
10
397
30
1203
50
2023
70
2851
90
3682
11
437
31
1244
51
2064
71
2893
91
3723
12
477
32
1285
52
2106
72
2934
92
3765
13
517
33
1326
53
2147
73
2976
93
3806
14
557
34
1366
54
2188
74
3017
94
3848
15
597
35
1407
55
2230
75
3059
95
3889
16
637
36
1448
56
2271
76
3100
96
3931
17
677
37
1489
57
2312
77
3142
97
3972
18
718
38
1530
58
2354
78
3184
98
4013
19
758
39
1571
59
2395
79
3225
99
4055
20
798
40
1612
60
2436
80
3267
100
4096
Experiment 1- Calibration of the Liquid in glass, Gas (vapour)
pressure and Bi-metal Devices
Aim
To show the linearity and accuracy of the liquid in glass, gas (vapour) pressure and Bi-metal devices, by
calibration against the reference sensor.
Procedure
1. Create a blank results table, similar to Table 13.
Calibrating Devices
Reference
Temperature
(°C)
Indicated
Temperature
(°C)
Deviation
(difference)
(°C)
Error
()
Table 13 Blank Results Table
2. Choose one of the liquid in glass thermometers. Put the reference sensor and the thermometer into
the icebox (through the holes in its lid). Wait a few minutes for the readings to stabilize and record
them (the reference temperature should be between 0°C and 1°C).
3. Now put both devices into the heater tank (through the holes in its lid). Switch on the heater and
note the reference temperature.
4. At intervals of 10°C (shown by the reference temperature), record the readings of the thermometer.
5. Stop the experiment and switch off the heater when the reference temperature reaches 100°C.
6. Repeat the experiment for the other liquid in glass thermometer, the gas (vapour) pressure
thermometer and the bi-metal thermometer. Allow the heater water to cool down (and change it
if necessary for cooler water) between tests.
Results Analysis
For each device, find the deviation and calculate the percentage error to complete your results tables.
Create charts of the indicated temperature (vertical axis) against reference temperature (horizontal axis).
Add to your charts, the reference temperature (against its own readings) to create a linear standard to
compare against the indicated readings.
On your results table, find the difference between the standard and your results (the deviation) and
calculate the percentage error.
Percentage error = (deviation/standard) x 100
Compare the devices against the standard to see which is the most accurate over the range.
Can you identify any possible causes of error.
Experiment 2 - NTC Thermistor Linearity
Aims
• To show how the NTC Thermistor works.
• To show the non-linearity of the NTC Thermistor.
Procedure
INPUT 1
INPUT 2
INPUT 3
INPUT 4
MILLIVOLTMETER
NTC THERMISTOR
100R
100R
R4
R3
1mA
WHEATSTONE
BRIDGE
100R
100R
NTC Thermistor
R2
Vx
REFERENCE
SENSOR
CONSTANT
CURRENT
SOURCE
R1
PRT SIMULATOR
CONSTANT
VOLTAGE
SOURCE
Figure 40 Connections for Experiment 3
1. Create a blank results table, similar to Table 14.
2. Connect the reference sensor to its socket and connect the NTC Thermistor to the millivoltmeter
and the constant current source as shown in Figure 40.
3. Put the reference sensor and the NTC Thermistor into the icebox (through the holes in its lid). Wait
a few minutes for the readings to stabilize and record them (the reference temperature should be
between 0°C and 1°C).
4. Now put both devices into the heater tank (through the holes in its lid). Switch on the heater and
note the reference temperature.
NTC Thermistor Calibration
Reference
Temperature
(°C)
Measured
Voltage
(mV)
Calculated
Resistance
()
Standard
Resistance
()
Deviation
()
Error (%)
Table 14 Blank Results Table
5. At intervals of 10°C (shown by the reference temperature), record the input 1 readings of the
millivoltmeter.
6. Stop the experiment and switch off the heater when the reference temperature reaches 100°C.
Results Analysis
Given that the constant current is 1 mA, use Ohm’s law (see Theory section) to calculate the resistance
of the Thermistor for each row in your table. You should see that is directly proportional to the measured
voltage.
Plot a chart of resistance (vertical axis) against temperature (horizontal axis).
Draw a best fit curve through your results to see how the NTC Thermistor gives a non-linear resistance
change over the range 0 to 100°C. Note how your results prove that resistance goes down as
temperature increases.
Add to your results table and chart, the standard resistances for the NTC Thermistor from Table 2 on
page 16 and compare the curves. On your results table, find the difference between the standard and
your results (the deviation) and calculate the percentage error.
Percentage error = (deviation/standard) x 100
Experiment 3: K Type Thermocouple Linearity
Aims
• To show how thermocouples work
• To show and compare the linearity and output signal levels of J and K type thermocouples
Procedure
INPUT 3 INPUT 4
INPUT 1 INPUT 2
MILLIVOLTMETER
WHEATSTONE
BRIDGE
REFERENCE
SENSOR
CONSTANT
CURRENT
SOURCE
PRT SIMULATOR
SOURCE
J - Type = Black
K - Type = Green
J - Type = White
K - Type = White
JUNCTIONS
Thermocouple
Figure 41 Connections for Experiment 6 - J and K Type Thermocouple Linearity
1. Create a blank results table, similar to Table 15.
2. Connect the reference sensor to its socket and connect the J or K type thermocouple to the amplifier
and the millivoltmeter as shown in Figure 40. The amplifier amplifies the small voltage from the
thermocouple by 20. This makes it suitable for the millivoltmeter. The actual voltage from the
thermocouple will therefore be 1/20 of the reading from the millivoltmeter.
3. Setup the heater and icebox as shown in Initial Setup (for Experiment 3 onwards) on
page 35.
4. Put the reference sensor and the thermocouple into the icebox (through the holes in its lid). Wait a
few minutes for the readings to stabilize and record them (the reference temperature should be
approximately 0°C).
5. Now put both devices into the heater tank (through the holes in its lid). Switch on the heater and
note the reference temperature.
J and K Type Thermocouple Calibration
Reference
Temperature
(°C)
Measured
Voltage
(mV)
Measured
Voltage/20
(V)
Standard
Voltage
(V)
Deviation
(mV or V)
Error (%)
Table 15 Blank Results Table
6. At intervals of 10°C (shown by the reference temperature), record the input 1 readings of the
millivoltmeter.
7. Stop the experiment and switch off the heater when the reference temperature reaches 100°C.
8. Repeat the procedure for the other thermocouple.
Results Analysis
Divide your millivoltmeter readings by 20 to find the actual measured voltage generated by the
thermocouples for each row in your table.
For each thermocouple, plot a chart of actual measured voltage (vertical axis) against temperature
(horizontal axis).
NOTE
If you have VDAS®, the software already has a divide by 20 data field.
Draw a best fit curve through each of your results to see how linear the voltage change is for each
thermocouple over the range 0 to 100°C. Note how your results prove that voltage goes up as
temperature increases.
Compare your results with the standard specifications for the thermocouples given in Table 3 on
page 17 and Table 4 on page 18.
On your results table, find the difference between the standard and your results (the deviation) and
calculate the percentage error.
Percentage error = (deviation/standard) x 100
Your results should be reasonably linear, but the deviation may be large and consistent (an offset). Can
you identify the causes of any errors? Hint - think about the thermocouples and the connections to the
amplifier.
Can you understand why thermocouple connections are important, and why you cannot simply connect
a thermocouple directly to an ordinary measuring device and expect it to work correctly?