STEP FOUR
TESTING THE WIRING
No wires should be connected to the control during the testing.
The following tests are to be performed using standard testing practices and procedures, and should only be carried out by properly
trained and experienced persons.
A good quality electrical test meter, capable of reading from at least 0 - 300 V (ac) and at least 0 - 2,000,000 Ohms, is essential to
properly test the wiring and sensors.
Test The Sensors
Ensure the sensor wires are not connected to the control terminals before testing. In order
to test the sensors, the actual temperature at each sensor location must be measured. A
good quality digital thermometer with a surface temperature probe is recommended for
ease of use and accuracy. Where a digital thermometer is not available, a spare sensor
can be strapped alongside the one to be tested, and the readings compared. Test the
sensors according to the following section.
Temperature
Resistance
Temperature
Resistance
Temperature
Resistance
Temperature
Resistance
°F
°C
°F
°C
°F
°C
°F
°C
-50
-46
490,813
20
-7
46,218
90
32
7,334
160
71
1,689
-45
-43
405,710
25
-4
39,913
95
35
6,532
165
74
1,538
-40
-40
336,606
30
-1
34,558
100
38
5,828
170
77
1,403
-35
-37
280,279
35
2
29,996
105
41
5,210
175
79
1,281
-30
-34
234,196
40
4
26,099
110
43
4,665
180
82
1,172
-25
-32
196,358
45
7
22,763
115
46
4,184
185
85
1,073
-20
-29
165,180
50
10
19,900
120
49
3,760
190
88
983
-15
-26
139,403
55
13
17,436
125
52
3,383
195
91
903
-10
-23
118,018
60
16
15,311
130
54
3,050
200
93
829
-5
-21
100,221
65
18
13,474
135
57
2,754
205
96
763
0
-18
85,362
70
21
11,883
140
60
2,490
210
99
703
5
-15
72,918
75
24
10,501
145
63
2,255
215
102
648
10
-12
62,465
80
27
9,299
150
66
2,045
220
104
598
15
-9
53,658
85
29
8,250
155
68
1,857
225
107
553
A good quality test meter capable of measuring up to 5,000 kΩ (1 kΩ = 1000 Ω) is required to measure the sensor resistance. In
addition to this, the actual temperature must be measured with either a good quality digital thermometer, or if a thermometer is not
available, a second sensor can be placed alongside the one to be tested and the readings compared.
First measure the temperature using the thermometer and then measure the resistance of the sensor at the control. The wires
from the sensor must not be connected to the control while the test is performed. Using the chart below, estimate the temperature
measured by the sensor. The sensor and thermometer readings should be close. If the test meter reads a very high resistance,
there may be a broken wire, a poor wiring connection or a defective sensor. If the resistance is very low, the wiring may be shorted,
there may be moisture in the sensor or the sensor may be defective. To test for a defective sensor, measure the resistance directly
at the sensor location.
Do not apply voltage to a sensor at any time as damage to the sensor may result.
Test The Sensor Wiring
Ω
Ω
V
Ω
12 of 20
© 2019 tekmar 256_D - 09/19