Troubleshooting Temperature Sensors - Daikin MicroTech Operation And Maintenance

Troubleshooting Temperature Sensors

The UVC is configured to use passive negative temperature
coefficient (NTC) sensor whose resistance decreases
with increasing temperature. The element has a reference
resistance of 10K ohms at 77°F (25°C). Each element is
calibrated as highlighted in Table 26 below.
Table 26: Temperature Versus Resistance
°F °C Ohms
-39 -39.44 323839
-37 -38.33 300974
-35 -37.22 279880
-33 -36.11 260410
-31 -35.00 242427
-29 -33.89 225809
-27 -32.78 210443
-25 -31.67 196227
-23 -30.56 183068
-21 -29.44 170775
-19 -28.33 159488
-17 -27.22 149024
-15 -26.11 139316
-13 -25.00 130306
-11 -23.89 121939
-9 -22.78 114165
-7 -21.67 106939
-5 -20.56 100218
-3 -19.44 93909
-1 -18.33 88090
1 -17.22 82670
3 -16.11 77620
5 -15.00 72911
7 -13.89 68518
9 -12.78 64419
OM 1280-2 • MICROTECH UNIT CONTROLLER
°F °C Ohms °F
11 -11.67 60592 61
13 -10.56 57017 63
15 -9.44 53647 65
17 -8.33 50526 67
19 -7.22 47606 69
21 -6.11 44874 71
23 -5.00 42317 73
25 -3.89 39921 75
27 -2.78 37676 77
29 -1.67 35573 79
31 -0.56 33599 81
33 0.56 31732 83
35 1.67 29996 85
37 2.78 28365 87
39 3.89 26834 89
41 5.00 25395 91
43 6.11 24042 93
45 7.22 22770 95
47 8.33 21573 97
49 9.44 20446 99
51 10.56 19376 101
53 11.67 18378 103
55 12.78 17437 105
57 13.89 16550 107
59 15.00 15714 109
Use the following procedure to troubleshoot a suspect sensor.
1. Disconnect both sensor leads from the UVC.
2. Using some other calibrated temperature sensing device,
take a temperature reading at the sensor location.
3. Use the temperature reading from Step 2 to determine
the expected sensor resistance from Table 26.
4. Using a calibrated ohmmeter, measure the actual
resistance across the two sensor leads.
5. Compare the expected resistance to the actual
resistance.
6. If the actual resistance value deviates substantially
(more than 10%) from the expected resistance, replace
the sensor.
°C Ohms °F
16.11 14925 111 43.89
17.22 14180 113 45.00
18.33 13478 115 46.11
19.44 12814 117 47.22
20.56 12182 119 48.33
21.67 11590 121 49.44
22.78 11030 123 50.56
23.89 10501 125 51.67
25.00 10000 127 52.78
26.11 9526 129 53.89
27.22 9078 131 55.00
28.33 8653 133 56.11
29.44 8251 135 57.22
30.56 7866 137 58.33
31.67 7505 139 59.44
32.78 7163 141 60.56
33.89 6838 143 61.67
35.00 6530 145 62.78
36.11 6238 147 63.89
37.22 5960 149 65.00
38.33 5697 151 66.11
39.44 5447 153 67.22
40.56 5207 155 68.33
41.67 4981 157 69.44
42.78 4766 159 70.56
62
Diagnostics and Service
°C Ohms °F °C
4561 161 71.67
4367 163 72.78
4182 165 73.89
4006 167 75.00
3838 169 76.11
3679 171 77.22
3525 173 78.33
3380 175 79.44
3242 177 80.56
3111 179 81.67
2985 181 82.78
2865 183 83.89
2751 185 85.00
2642 187 86.11
2538
2438
2343
2252
2165
2082
2003
1927
1855
1785
1718
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Ohms
1655
1594
1536
1480
1427
1375
1326
1279
1234
1190
1149
1109
1070
1034