www.DaikinApplied.com 63 OM 1280-2 • MICROTECH UNIT CONTROLLER
Troubleshooting Humidity Sensors
CAUTION
The humidity sensor is not protected against reversed polarity. Check
carefully when connecting the device or damage can result.
capacitive humidity sensor. Each sensor is calibrated according
to the table shown.
Use the following procedure to troubleshoot a suspect sensor:
1. Disconnect the sensors output voltage lead from the
UVC analog input.
2. Using some other calibrated humidity sensing device,
take a humidity reading at the sensor location.
3. Use the humidity reading from Step 2 determine the
expected sensor voltage from Table 27.
4. Using a calibrated multi-meter, measure the actual
voltage across the yellow and white sensor leads.
5. Compare the expected voltage to the actual voltage.
6. If the actual voltage value deviates substantially (more
than 10%) from the expected voltage, replace the sensor.
• White = ground
•
• Blue = supply VDC
Table 27: Humidity Versus Voltage
RH (%) VDC (mV) RH (%) VDC (mV)
10 1330 55 2480
15 1475 60 2600
20 1610 65 2730
25 1740 70 2860
30 1870 75 2980
35 1995 80 3115
40 2120 85 3250
45 2235 90 3390
50 2360 95 3530
Troubleshooting Carbon Dioxide
(CO
2
) Sensors
single beam absorption infrared gas sensor. Each sensor is
calibrated according to the table shown.
Use the following procedure to troubleshoot a suspect sensor.
1. Disconnect the sensors output voltage lead from the
UVC analog input (AI-14).
2. Using some other calibrated CO
2
sensing device, take a
CO
2
reading at the sensor location.
3. Use the CO
2
reading from Step 2 to determine the
expected sensor voltage from Table 28.
4. Using a calibrated multi-meter, measure the actual
voltage across the lead removed from AI-14 and ground.
5. Compare the expected voltage to the actual voltage.
6. If the actual voltage value deviates substantially (more
than 10%) from the expected voltage, replace the sensor
In the unlikely event that the CO
2
sensor requires calibration,
consult the factory for information on obtaining calibration
equipment and instructions.
Table 28: CO
2
Versus Voltage
CO
2
(PPM) VDC (V) CO
2
(PPM) VDC (V)
300 1.5 1200 6.0
400 2.0 1300 6.5
500 2.5 1400 7.0
600 3.0 1500 7.5
700 3.5 1600 8.0
800 4.0 1700 8.5
900 4.5 1800 9.0
1000 5.0 1900 9.5
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