Pressure transmitter signal issues
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Dear colleagues, our unit has a simple pressure transducer that operates on a 24V two-wire system; the signal is sent directly to the S7-200 module EM231CN. Recently, the pressure values displayed on the controller have been fluctuating greatly. When a signal source is used on-site to supply the signal, the pressure values remain stable. We have even replaced the pressure transducer, but the problem persists. The cable connecting the pressure transducer to the PLC is less than 5 meters long. I would appreciate any advice from you all. Thank you
By providing a stable signal at the site using a signal source, it is possible to determine that there are no issues with the wiring or interference; check whether the fluctuations in the process parameters are excessive.
If you can rule out any fluctuations in process pressure, then it must be that the new pressure transformer you’re using has poor interference resistance; it’s probably a defective product. If the power supply is built into the circuit board, it can be disabled; try using an external power supply instead! . For example, switch to a linear isolated power supply for power supply. If that still doesn’t work, then just take it apart and use it as a toy to hit dogs with, :P And then, come to me, your brother, and buy a small voltage regulator with excellent interference resistance. {:3_51:}
The last edit to this post was made by 1111111 on 2017-12-3 at 14:49. Just how strong is the interference resistance of the small transformer in my village? The reliable resolution of the signal is as high as one in a hundred thousand of the full scale, that is, 0.001% FS. . . . . And ordinary voltage transformers don’t even reach 0.01% FS
Check on-site whether the voltage transformer readings fluctuate There must be reality, right?
Does the voltage transformer have an on-site display? Based on your description, it seems that the actual output of the voltage transformer does change.
The absence of interference when using a current source does not mean there will be no interference after connecting a voltage transformer; many sampling chips used in voltage transformers have very poor interference resistance. It is recommended to conduct a cross-test using a voltage transformer that is working properly in another location.
I personally suspect that fluctuations in the process parameters at the site are quite likely
That is, the actual pressure is fluctuating, or it could be due to issues with the pressure guide tube; if there is heating, check that as well
Use a meter with a better interference resistance circuit board for channel switching