Chapter 3. Calibration and Troubleshooting
18
DewPro<Superscript>® MMR31 Installation & Operation Manual
3.3
Troubleshooting
3.3.1
Loop Current is Out of Range
3.3.1.1
Unit of Measure is RH
Note:
0% and 100% relative humidity are absolute limits. However, a defective sensor or a malfunction of the sensor
electronics could generate sensor signal values which are outside the 0-100% range. If the sensor signal
value is above 100% or below 0%, the current will go to the fault current specified on the order or in the matrix
field VH 07.
Solution:
Expose the sensor to ambient air which normally has a relative humidity between 10% and 90%. If the
current returns the 4–20 mA range, check the sensor calibration (see
“Calibration Steps” on page 16
). However, if the
current remains in error mode contact Panametrics for assistance.
3.3.1.2
Unit of Measure is Dew Point
Solution 1:
The process dew point is out of range. If the dew point is above 185°F (85°C), the current will go to the fault
current specified on the order or in the matrix field VH 07. Apply dry air for a few minutes. If the current remains in error
mode contact Panametrics for assistance.
Solution 2:
If the dew point is below 5°F (–15°C), the current will go to the fault current specified on the order or in the
matrix field VH 07. Move the sensor into a wetter environment for a few minutes. If the dew point doesn't increase, the
cause may be a defective sensor assembly or an electronics malfunction. Contact Panametrics for assistance.
Note:
The same approach is valid for the other available units of measure and for the second loop (temperature).
3.3.2
No Loop Current
Solution:
Check the voltage and polarity across the positive (+) and negative (-) terminals of the MMR31 with a DC
voltmeter. If the voltage is within the 12-28 VDC range, contact Panametrics for assistance.
3.3.3
Slow Response Time
Solution:
Remove the protective filter cap by turning it counter-clockwise, and clean it with air flow or a solvent. If the
sensor filter is contaminated, clean it with hot water using a brush.
3.3.4
Frozen Output Current
Solution:
Check
Switch S3
, which should be in position 0, 1, 2, 3, 8 or 9.