Reasons and solutions for Magnetic flow meter showing negative values

The failure of the electromagnetic flowmeter during operation is often caused by factors such as the adhesion
layer on the liner of the flow sensor, lightning electric shock and environmental conditions. If the electromagnetic
flowmeter has a negative flow value during use, there are likely to be several reasons. 
1. Electromagnetic flowmeter sensor is not installed according to the flow direction indicator, causing the flow
to be reversely measured. At this time, the instantaneous flow rate is a negative value.
Solution: Reinstall the electromagnetic flowmeter and follow the sensor flow direction.
2. Signal line of the flow sensor is reversed. The electromagnetic flowmeter has the function of forward and
reverse measurement, so the reverse flow will be displayed.
Solution: The sensor signal line can be switched correctly.
3. The pipe is empty or the liquid is not filled, and there are air and bubbles. At this time, the phenomenon that the 
negative number or the flow value is suddenly large or small is displayed.
Solution: The shrinkage or tilting installation can be used to fill the pipe with the measured medium, which allows the
flowmeter to have measurement conditions.
There is also a case where the flow rate of the electromagnetic flowmeter is negative. When the valve is opened, 
the instantaneous flow will cause the pipe liquid to recirculate, resulting in a negative value.



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