Seeking help from experts regarding Siemens S7200
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I ran into a problem today with Siemens’ SU200AI module: one of its channels is connected to a flow meter. The computer shows large fluctuations in flow rate, but the flow meter itself is stable, and the current readings are also stable. When checking the program on the computer, fluctuations are indeed present; the filtering settings are all correct. The fluctuations decrease when a signal generator is used to supply a signal, and I’ve also checked the grounding connections, ensuring that the M terminal is properly grounded. Yet, the issue of fluctuating readings persists. In the end, I even replaced the module, but the problem remained. Has anyone encountered this situation? Could you please offer some guidance? Please
Ground the flow meter, use shielded twisted pair cable, add an isolation barrier, and so on
Is the signal generated from the field primary meter? Is there a safety barrier?
It is caused by line interference. A few people upstairs introduced the methods.
Is the instrument cable unshielded, requiring single-ended grounding?
It was tested through the direct connection as well as on-site, and the fluctuations are the same in both cases. All that’s left now is to replace the power supply cable; I’ll shut down the system and try connecting a new instrument power supply
If there is an inverter in the distribution cabinet, add filtering
Whether the power cable is shielded, or there is interference from high-frequency or low-frequency equipment on site, or from the power supply of other devices. I personally think it’s still a problem with the transmission channel.
We have encountered this before: with 4 analog input channels, if they are not in use, they must be short-circuited; they cannot remain unused