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  • MVP 2023

I think it's a futile request. Sometimes vibration sensors can be affected by noise, or higher frequency vibration that isn't useful to measure. For instance, with a large pump or motor, you're probably looking at seeing a problem with a rotational bearing, or something similar, which will result in a low frequency vibration. Any high frequency vibration might mask the signal you're looking for or cause false positives. I know it can be a common practice to place an electrical low-pass filter between the sensor and the ultimate measuring device, but I was thinking maybe there was a software way to accomplish this. I suspect there is really very little (or no) frequency information available to the PLC on the 4-20mA analog input, but thought I would check it out anyway.

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Low-pass filter in Ladder is more like to DSP (Digital Signal Processing), which require special hardware module, or lot of resources.

Some PLCs have a Filter option in Hardware Configuration, and other PLCs can use Filter option from FB's Menu.

Please look an next link from Control Engineering:

Ladder logic 402: Data manipulation and filtering. Frank Lamb.


Please remember, that conversion time for analog inputs will be number of system scans.



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