IOM-WR-Snow_Ice-090_09 324
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When performing these tests:
The sensor head should be installed in the slab.
The five cable wires at the control should be disconnected.
Use a good quality electrical testing meter with an ohm scale range of 0 to
2,000,000 Ohms.
The sensor has two 0k Ohm thermistors. One reads slab surface temperature, and
the other checks sensor heater temperature.
If the sensor has been disconnected from the control for an hour or more, the readings
for both thermistors should be very close.
Using the ohmmeter and standard testing practices, measure the resistance
between:
(a) the yellow and black sensor wires (sensor temperature), and
(b) the brown and black sensor wires (slab temperature).
The table below lists the expected resistance values at various sensor temperatures.
Measure the resistance between the blue and black wires. When the sensor surface
is dry, the reading should be 2,000,000 Ohms. When the sensor surface is wet it
should be between 0,000 and 300,000 Ohms.
Measure the resistance between the red and black wires of the heating element. This
reading should be close to 50 Ohms.
•
•
•
Temperature
Resistance
°F
°C
-50
-46
490,83
-45
-43
405,70
-40
-40
336,606
-35
-37
280,279
-30
-34
234,96
-25
-32
96,358
-20
-29
65,80
-5
-26
39,402
-0
-23
8,08
-5
-2
00,22
0
-8
85,362
5
-5
72,98
0
-2
62,465
5
-9
53,658
20
-7
46,28
25
-4
39,93
Temperature
Resistance
°F
°C
30
-
34,558
35
2
29,996
40
4
26,099
45
7
22,763
50
0
9,900
55
3
7,436
60
6
5,3
65
8
3,474
70
2
,883
75
24
0,50
80
27
9,299
85
29
8,250
90
32
7,334
95
35
6,532
00
38
5,828
05
4
5,20
Step 4 - Test the Sensor
Temperature vs. Resistance Table
