23MHGRVX-B2 Module Technical Guide
TROUBLESHOOTING
Other Checks
Supply Air Temperature Sensor
If you suspect the Supply Air Temperature Sensor is not reading
correctly, make sure the wiring terminal connections are tight and
that any wiring splices are properly connected. You can check the
operation of the Supply Air Temperature Sensor by measuring the
resistance or voltage using a digital multimeter.
Measuring Voltage
Set the meter to DC Volts. Place the positive probe on the AIN
terminal and the negative probe on the GND terminal. Read the
DC Volts and nd that voltage in Table 6, this page and Table 7,
page 24. Read the temperature corresponding with that voltage
and determine if this is close to the actual temperature the sensor is
exposed to. If the temperature from the chart is dierent by more than
a few degrees, you probably have a defective or damaged sensor.
Thermistor Sensor Testing Instructions
1. Use the resistance column to check the thermistor sensor
while disconnected from the controllers (not powered).
2. Use the voltage column to check sensors while connected
to powered controllers. Read voltage with meter set on
DC volts. Place the “-” (minus) lead on GND terminal
and the “+” (plus) lead on the sensor input terminal being
investigated.
Measuring Resistance
To read the resistance, set the meter to Ohms. Unplug the sensor
connector from the board and measure the resistance across the
disconnected wires. This resistance should match the corresponding
temperature from Table 6, this page, and Table 7, page 24.
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
-10 -23.3 93333 2.98
-5 -20.6 80531 2.94
0 -17.8 69822 2.89
5 -15 60552 2.83
10 -12.2 52500 2.77
15 -9.4 45902 2.71
20 -6.6 40147 2.64
25 -3.9 35165 2.57
30 -1.1 30805 2.49
35 1.7 27140 2.41
40 4.4 23874 2.33
45 7.2 21094 2.24
50 10 18655 2.15
52 11.1 17799 2.11
54 12.2 16956 2.08
56 13.3 16164 2.04
58 14.4 15385 2.00
60 15.6 14681 1.96
62 16.7 14014 1.93
64 17.8 13382 1.89
66 18.9 12758 1.85
68 20 12191 1.81
69 20.6 11906 1.79
70 21.1 11652 1.78
71 21.7 11379 1.76
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
72 22.2 11136 1.74
73 22.8 10878 1.72
74 23.3 10625 1.70
75 23.9 10398 1.68
76 24.4 10158 1.66
78 25.6 9711 1.63
80 26.7 9302 1.59
82 27.8 8893 1.55
84 28.9 8514 1.52
86 30 8153 1.48
88 31.1 7805 1.45
90 32.2 7472 1.41
95 35 6716 1.33
100 37.8 6047 1.24
105 40.6 5453 1.16
110 43.3 4923 1.09
115 46.1 4449 1.02
120 48.9 4030 .95
125 51.7 3656 .88
130 54.4 3317 .82
135 57.2 3015 .76
140 60 2743 .71
145 62.7 2502 .66
150 65.6 2288 .61
TEMPERATURE TO RESISTANCE/VOLTAGE CHART
Table 6: 0-3V Temperature Sensor - Voltage and Resistance for Type III Sensors
Note: If the voltage is above 3.3 VDC the sensor or wiring is “open.” If the voltage is less than 0.05 VDC, the sensor or wiring is shorted.
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