Garbled 485 communication in electromagnetic flowmeters
Thread Content
There is an electromagnetic flowmeter at the wastewater treatment site, used to measure the flow rate of the treated water; these data are collected by a data acquisition device and uploaded to the platform of the municipal environmental protection agency； Data transmission between the electromagnetic flowmeter and the data acquisition unit is achieved via 485 communication. At first, the operation of the equipment and data transmission were both normal. After some time, garbled characters appeared on the data acquisition unit (sometimes normal and sometimes garbled), while the flow rate displayed on the local display of the electromagnetic flowmeter was normal; it could be determined that the issue lay in the 485 communication between the electromagnetic flowmeter and the data acquisition unit. The digital data acquisition instrument manufacturer said the problem wasn’t on their end; when the flow meter’s display was taken to the manufacturer for testing, it was found that the 485 communication was also working properly. Has anyone encountered this situation? Or what are some places that can be checked?
The pipeline section of the magnetic flowmeter should not have high leakage currents, and it should be properly grounded in its vicinity. Check whether such a situation exists; this is what comes to mind
1. Replace with high-quality shielded twisted pair cable. 2. Use a RC network for filtering to reduce noise. 3. Reduce the baud rate for lower-speed communication
1. The communication parameters between the data acquisition instrument and the flow meter are not consistent, including address, baud rate, parity, stop bit, etc； 2. Poor communication quality, mainly due to issues with the shielding of the communication cables; if the communication distance is large, it is recommended to increase the terminal resistance ； 3. Fault in the data acquisition instrument.
It seems the data acquisition instrument has a bigger problem.