Michell Instruments Optidew User Manual page 52

APPENDIX C
Symptom: Peltier power cooling 100%
Cause
Resolution
Cause
Diagnosis
Resolution
Cause
Diagnosis
Resolution
Cause
Diagnosis
Resolution
Symptom: Temperature reading -100 or +473, or does not change
Cause
Resolution
Cause
Diagnosis
Resolution
Cause
Resolution
44
LED too bright (mirror condition not set correctly)
Set mirror condition during DCC cycle as per instruction in Section 5
(Maintenance)
Ensure red sensor LED brightness changes as potentiometer is adjusted
Sensor cable not connected or damaged
Try another sensor cable
Ensure continuity of sensor cable conductors i.e. Pin A – Pin A continuity
Ensure sensor cable connections are sound
Source replacement sensor cable from local Michell Instruments'
representative
Dew point below measurement capability of sensor
Check maximum depression from ambient temperature of 20°C meets
criteria, by using the MAXCOOL function:
Single Stage: 50-55°C
Dual Stage: 60-65°C
Metal Body (Aluminum, Stainless Steel): 40-45°C
If the maximum depression does not meet specifi cation, ensure the sensor
is suffi ciently ventilated to remove build-up of heat generated when the
heat pump is cooling. High ambient temperatures will limit the depression
range of the sensor.
If the maximum depression is within the specifi cation above, then the dew
point may be below the measurement capabilities of the sensor. In this
case contact Michell Instruments for further advice.
Photo detector fault
Block light from red sensor LED to mirror using cotton bud.
Ensure mirror condition increases (to 100% or close)
Contact Michell Instruments' Service department
Optidew set to CMDT mode
Connect via RS232 / Hyperterminal, send the command: 'opti'
Remote PRT damaged
Try another Remote PRT
Check all resistances
This is a 4 wire PRT: pins 1 and 3 should be short circuit; pins 2 and 4
should be short circuit
The resistance between pins 1 and 2 or pins 3 and 4 should be ~108 Ω
@ 21°C
Source replacement PRT from Michell Instruments Ltd
Instrument hardware fault
Contact Michell Instruments' Service department
Optidew Series User's Manual
97430 Issue 2, March 2017