Why is my Michell Instruments Optidew showing a dew point reading of -100 or +473?
This issue may arise due to a disconnected or damaged sensor cable. Ensure that all sensor cable connections are secure. If the problem persists, the sensor PRT might be damaged, indicating an open or short circuit, or there could be an instrument hardware fault. In such cases, contact Michell Instruments’ Service department for assistance.
What to do if my Michell Instruments Optidew shows a fixed 100% mirror condition with constant heating?
This problem may occur if the LED is too dim, meaning the mirror condition is not correctly set. You should set the mirror condition during the DCC cycle. Make sure the red sensor LED brightness changes when the potentiometer is adjusted. Also, check that the sensor cable is properly connected and not damaged. If light is not detected, there may be a photo detector fault.
What to do if my Michell Instruments Optidew Measuring Instruments displays a temperature reading of -100 or +473, or the temperature doesn't change?
This issue can occur if the Optidew is set to CMDT mode. To resolve this, connect via RS232 / Hyperterminal and send the command ‘opti’. Another potential cause is a damaged remote PRT, which would need to be replaced. You can source a replacement PRT from Michell Instruments Ltd. If neither of these solutions works, there may be an instrument hardware fault.
What to do if my Michell Instruments Optidew shows a fixed 0% or flashing 0% (low) mirror condition with constant cooling?
This issue can be caused by an LED that is too bright, indicating the mirror condition is not correctly set. Set the mirror condition during the DCC cycle and ensure the red sensor LED brightness changes as the potentiometer is adjusted. Also, ensure the sensor cable connections are sound and not damaged. Another possible cause is a photo detector fault.
Why is my Michell Instruments Measuring Instruments dew-point reading showing ambient or a fixed temperature?
This issue may be due to a sensor cable that is either not connected or damaged; ensure the sensor cable connections are secure. Alternatively, the heating or cooling transistor on the instrument may be damaged. Another potential cause is a damaged heat pump, or an instrument hardware fault.
How to troubleshoot unstable dew-point readings on Michell Instruments Optidew?
Unstable dew-point readings can be caused by a dirty mirror. Clean the mirror according to the instructions in the manual and set the mirror condition during the DCC cycle as per the manual instructions. Also, a problem with the measurement technique may cause this issue.
Why is my Michell Instruments Optidew Peltier power cooling at 100%?
This can happen if the LED is too bright, meaning the mirror condition is not set correctly. You should set the mirror condition during the DCC cycle, ensuring the red sensor LED brightness changes as the potentiometer is adjusted. Also, check the sensor cable connections to ensure they are sound and not damaged. The dew point may also be below the measurement capability of the sensor. Ensure the sensor is sufficiently 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 specification, then the dew point may be below the measurement capabilities of the sensor. Another possible cause is a photo detector fault.
How to fix cannot connect to HyperTerminal / Optisoft issue on Michell Instruments Measuring Instruments?
If the unit has a display, ensure it is in REMOTE MODE by holding the display button for approximately 7 seconds. If the unit is an RS485 / RS422 communications version, you will need an appropriate RS232 to RS422 or RS485 adapter to connect to a standard RS232 port on a PC. It is also possible that the serial ports have stopped responding on the host PC. In this case, restart Optidew and restart the host PC / equipment.
Why is my Michell Instruments Optidew dew-point reading in error?
If the dew point is less than 0°C, the error may be due to the Optidew measuring super-cooled water on the mirror instead of ice. The error will be approximately 10% of the reading. Refer to guide in appendices. If the error is greater than 0.5°C when checking against a reliable, recently calibrated reference, there is likely a problem with the internal PRT or the instrument electronics require calibration. Return to service department for service and calibration.
General| Sensor Type | Chilled Mirror |
|---|---|
| Measurement Range (Relative Humidity) | 0 to 100 %RH |
| Resolution | 0.01 °C DP |
| Operating Temperature Range | -20°C to +60°C |
| Operating Humidity Range | 0 to 100 %RH |
| Output | 4-20 mA, RS485 |
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