Abnormal phenomena in the use of pressure transmitters with PLCs
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The two existing hydraulic pressure transmitters for the synthetic cycle oil showed a value of 0.32 MP when operating properly on the PLC. One day, both of them suddenly showed a value of 0.53 MP, with fluctuations around 0.2 MP. I recalibrated the transmitter and checked the wiring——I checked almost everything that could be checked, but I still can’t find the cause. Later, I returned to normal. Can anyone tell me why?
Is it a shielding issue or a grounding issue?
Generally, PLC analog input cards have poor interference resistance; it is recommended to use isolation modules. Make sure proper shielding and grounding are in place.
That’s a good point; I agree with this view
It is likely a problem with shielding and grounding; in intrinsically safe systems, this can be resolved using isolated safety barriers, while in ordinary industrial systems, isolators (which are cheaper) can also be used to solve the issue.
As mentioned on the third floor, isolators and similar devices are usually required; the signal passes through these isolators before reaching the PLC. The problem in your case is likely caused by some kind of interference. You can try connecting a standard signal directly to the PLC to identify the issue using the method of elimination.
If it is incorrect again, measure the circuit current and calculate the corresponding pressure value to determine whether the issue lies with the transmitter or the PLC’s measurement circuit. To enhance shielding, use a single point of grounding
Could it be caused by voltage fluctuations? Interference is also a possibility. Is it real pressure?/ Consider it from various aspects
Do you mean that it’s sufficient to ground the system and ensure proper shielding, is that right? Thank you
Very good, thank you to the original poster!:handshake
I also think the cause should be sought in external factors, such as power supply, interference, grounding, hardware, and so on.
There are generally no issues with the PLC’s programming; when problems do occur, it’s important to check whether there are any large electrical devices on site, such as welding machines.
Thank you all for your participation! I have measured the current and voltage, and both are normal. It should be a shielding issue.
Please check the interference from the frequency converter! ! !