Fluidpowerman Posted August 17, 2017 Report Share Posted August 17, 2017 Working on a project with several UIA-0800A analog input modules. We are using all 4-20 ma transducer input. Pressure, Flow, Weight(load cell), pH. the only difference is for some of the transducers we power the loop thru and external power supply (24VDC) for the pressure transducers. results are solid. Others the loop power is provided by the transducer. For example for the Load cells the scale provides an 4-20 ma output signal with loop power to the UIA-0800A. What is very strange is the input signal floats around at a slow steady pace. including going below 4 ma. at first the number will appear solid then it will slowly drift down below 4ma down to zero and then will slowly climb back to a fairly accurate reading. It continually oscillates over a 1-3 min cycle. Very strange . My question is has anyone experienced this problem, and is there a minimum voltage required into the card. some of the loop power from the sensors are less than 24VDC more like 15 Any input is greatly appreciated FPM Quote Link to comment Share on other sites More sharing options...
MVP 2022 Joe Tauser Posted August 22, 2017 MVP 2022 Report Share Posted August 22, 2017 It sounds like your 0V reference is floating between the scale and the input module. Is the ground from the scale head tied to the ground of the panel? What type of scale head are you using? Joe T. Quote Link to comment Share on other sites More sharing options...
MVP 2022 Ausman Posted August 22, 2017 MVP 2022 Report Share Posted August 22, 2017 On 17/08/2017 at 9:32 PM, Fluidpowerman said: external power supply Have you tried running everything from the one supply? cheers, Aus Quote Link to comment Share on other sites More sharing options...
Milinda Posted April 28, 2021 Report Share Posted April 28, 2021 I have faced similar problem in 2 projects.can you explain how overcome this issue? 1 Quote Link to comment Share on other sites More sharing options...
MVP 2022 Ausman Posted April 28, 2021 MVP 2022 Report Share Posted April 28, 2021 Milinda, as Fluid did not respond we are all in the dark. However, Joe's answer is a good place to start. With a good meter, check all the 0 V terminations amongst themselves over the period of time. Some other things to do as well..... Ensure that all control supplies are running from the same phase. If you run the sensor as standalone and monitor it's output without it being connected to the plc, what happens? If this doesn't show anything up then please advise type of sensor and circuit layout done. cheers, Aus Quote Link to comment Share on other sites More sharing options...
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