MVP 2023 Flex727 Posted March 16, 2017 MVP 2023 Report Share Posted March 16, 2017 Has anyone ever tried to implement a rudimentary low-pass filter in ladder logic? Is it even practical? Quote Link to comment Share on other sites More sharing options...
MVP 2023 Ausman Posted March 16, 2017 MVP 2023 Report Share Posted March 16, 2017 More info please, Flex! cheers, Aus Quote Link to comment Share on other sites More sharing options...
MVP 2023 Flex727 Posted March 16, 2017 Author MVP 2023 Report Share Posted March 16, 2017 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. Quote Link to comment Share on other sites More sharing options...
hotwires Posted March 17, 2017 Report Share Posted March 17, 2017 They have the 50 or 60 Hz noise rejection settings on Unistream 8 ch AI, I suspect it is a software based notch filter. A ladder based filter while not impossible would be a bit over my head. Good notion, Nobody likes false alarms or measurements! Quote Link to comment Share on other sites More sharing options...
AlexUT Posted March 19, 2017 Report Share Posted March 19, 2017 Hi, 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. http://www.controleng.com/single-article/ladder-logic-402-data-manipulation-and-filtering/e589114a10276058909584cea125cbcf.html Please remember, that conversion time for analog inputs will be number of system scans. B.R. 1 Quote Link to comment Share on other sites More sharing options...
MVP 2023 Flex727 Posted March 19, 2017 Author MVP 2023 Report Share Posted March 19, 2017 Great source. Thank you, AlexUT! Quote Link to comment Share on other sites More sharing options...
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