Siemens SITRANS F M MAG 5100 W Operating Instructions Manual page 36

Troubleshooting/FAQs
7.1 Sensor check
Sensors with an insulation resistance down to 1 Megohms may still work satisfactorily but
this is not guaranteed.
Electrode resistance check
● Measure the electrode resistance between connections 82 and Zero with a moving coil
● Repeat the resistance measurements between connections 83 and Zero.
If the resistance is low there may be a short on the electrodes or wiring (in the case of a
remote mounted transmitter). Alternatively there may be water ingress or moisture in the
terminal box.
If the resistance is high and the pipe is completely full of fluid check the following:
1. The fluid is electrically conductive.
2. Electrodes are not coated with grease or any deposit.
3. Electrode circuit is not open
4. The remote mounted transmitter has a 3 core cable with an overall shield continuously
5. The shield is connected to the Zero or to the earth terminal (PE) on the sensor.
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meter.
With a sensor full of fluid the resistance should be between 5Kohms and 50Kohms.
If the sensor is empty the resistance will be infinite.
The results should be the same.
from the sensor to the transmitter, including junction boxes and terminal rails inside
panels.
NOTICE
Sensors removed from line
For sensors removed from line with dry bore, use megger between terminal 82 and
compression plate, and 83 and compression plate to show any water ingress behind
electrodes or within enclosure.
SITRANS F M MAG 5100 W
Operating Instructions, 11/2010, A5E03063678-02