Why is there fluctuation in the electromagnetic flowmeter?
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An electromagnetic flowmeter sensor without an on-site display was installed on the 300-mm diameter circulation water pipe at the site; two shielded cables were used to connect it to the control room, which is 10 meters away (the total length of the cables is 30 meters). Even when both the inlet and outlet water flows were shut off, there was still an instantaneous flow rate, and the value of this instantaneous flow rate varied – sometimes it was over 1000, sometimes over 5000, and at other times it was around 100. PS: We have tested the valves for inlet and return water, and they seem to be leak-free. A voltage of around 0.1V was detected between the gauge casing and ground, but I have used an 1.2-meter iron pipe to create a temporary ground connection; now the voltage between the gauge casing and ground is 0.002V. The manufacturer conducted an experiment: after powering on a new flow meter, 24V was applied to the grounding terminal. A voltage of 0.19V could be measured between the meter’s casing and ground, but it was normal for the flow meter not to stop operating. Does anyone here have any suggestions on what might be causing the problem?
There is interference; check the grounding
Electromagnetic flowmeters have strict requirements regarding shielding: not only must the gauge head be grounded, but the instrument itself also requires a reliable grounding to block out interference signals.
Look carefully – we have checked the grounding, and it is now connected to the iron rod through a separate grounding wire. Moreover, tests conducted by the manufacturer show that slight interference has no impact
We are sensors; the flanges of the instrument body as well as the secondary instruments are all grounded
Check if there are any high-voltage or strong-magnetic devices nearby
Are the instrument side and the laboratory side grounded together?
I’ve tried turning it on and off
The equipment nearby consists at most of a few water pumps, and none of them are in use – the factory is under maintenance