Cologne electromagnetic flowmeter
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Why do the readings of a Coriolis electromagnetic flowmeter all show negative values? Upon inspection, it was found that while the PLC supplied power to the flow meter, the flow meter itself also had a signal voltage. After changing the connection method of the flow meter to a passive one, it displayed \"zero\" from time to time. There will be a reading for a while, but it’s not high and the fluctuations are very frequent. What’s going on?
Can this flow meter be active or passive?
Can cloned electromagnetic flowmeters be active? Active and passive generally refer to whether a two-wire instrument is powered or not; electromagnetic flowmeters are usually four-wire instruments, with one set of cables used for power supply and another set for transmitting signals. The signals are passive, right? Since the instrument has its own power source and can transmit active signals, the signals received in the control room are passive in nature……
What is the status of the flow meter as well? Air traffic control? Full pipe? Will the flow of the medium in the pipe continue or stop?
First, clarify whether it is the surface panel that shows negative values or the back-end system, and also specify what state the medium inside the pipeline is in.
If the pipe is full and the fluid is at rest； So, check the grounding and potential balance ； ； Are there bubbles in the fluid? ； ； Low traffic volume – simply cut off the low-traffic flow
Whether the pipeline is empty or full; if it’s full, cutting off the flow at a low level is still indicated, but what gets cut off here is the flow rate
If the flow meter is not in use, there may be residual liquid in the electrodes； If it’s in use, it might be due to insufficient monitoring; turn on the air traffic control monitoring to check. If that still doesn’t work, then check whether the header is properly grounded, and whether the shielding layer of the signal wires on the PLC side is properly grounded, as electromagnetic interference could be the issue.
This obviously has nothing to do with your PLC
The surface panel shows a negative value, indicating medium flow, but the pipe is not full
It is meaningless to discuss dissatisfaction with full flow; full flow is a necessary condition for the operation of an electromagnetic flowmeter.