Analyze the reasons
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There are several electric float level gauges that transmit data to the DCS system via safety barriers; the readings shown by these gauges fluctuate. A 24V switching power supply has been replaced, the safety barriers have been checked, and the grounding system has also been inspected. Process-related issues have been ruled out, and interference is suspected as the cause, but the source of this interference cannot be identified. Please help analyze what might be causing this problem.
What medium? Specify whether heating is provided and what form the heating takes
The measuring medium is oil. No heat tracing
Is the selection of the safety barrier correct? Check the safety barrier again
Going directly to the card terminal without going through the safety barrier – it’s the same in this case as well
So frequently, connect a multimeter in series to measure and see if there is a significant change
It’s not that safety barriers cannot be used; in cases where they are necessary, it is recommended to use isolated safety barriers
The change in current is consistent with the change in trend
There is still an overall trend, but there are interfering factors; identifying the source of these interferences will resolve the issue
A float is a variable buoyancy type level gauge; it’s not suitable for measuring oil, right? The viscosity and density of oil have too great an impact on the measurement
In your case, it goes into the DCS through a safety barrier, and the safety barrier itself has isolation functionality