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