Michell Instruments Optidew User Manual page 53

Optidew Series User's Manual
Symptom: Dew-point reading in error
Cause
Resolution
Cause
Resolution
Symptom: Dew-point reading unstable
Cause
Resolution
Cause
Resolution
Michell Instruments
If dew point < 0°C then error may be due to Optidew
measuring super-cooled water on the mirror instead of ice.
Error will be approximately 10% of reading
Refer to guide in appendices
Internal PRT damaged or instrument electronics require
calibration
If error > 0.5°C when checking against a reliable, recently calibrated
reference, there is likely a problem with the instrument
Return to service department for service and calibration
Mirror is dirty
Clean mirror according to instructions in manual
Set mirror condition during DCC cycle as per manual instructions
Problem with measurement technique
Contact Michell Instruments. Provide the following information:
• Flow rate
• Temperature
• Pressure
• Gas composition
• Expected dew point
• Logged data (if available)
• Description of application (e.g. measuring relative
humidity in an environmental chamber)
APPENDIX C
45