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Diagnostics and Troubleshooting
7.1
Sensor check
Requirement
To check the SITRANS FM sensors the following test instruments will be required:
• Digital Meter/Multimeter
• Ohmmeter "Megger"
• (Moving Coil Meter)
Sensor check
Remove the transmitter from the sensor or remote position before making the following checks.
Coil resistance check
• Measure the coil resistance between connection numbers 85 and 86 using a digital meter.
Resistance should be within range stated in Coil resistance table (Page 64).
A low reading may indicate moisture within the coil housing or shorted coil turns.
A high reading would indicate an open circuit coil.
Note
In case of deviation from nominal coil values, the sensor is damaged and must be replaced
Coil insulation check
Potential hazard!
Only carry out a coil insulation check in non-hazardous area!
• Megger between connection number 85 and the sensor body.
The resistance should be above 20 MΩ.
A low megger reading would indicate the coil insulation is breaking down. This is usually due
to fluid ingress into the coil housing.
Sensors with an insulation resistance down to 1 MΩ may still work satisfactorily but this is
not guaranteed.
SITRANS FMS500
Operating Instructions, 01/2024, A5E52677520-AA
WARNING
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