4-20ma Rescaling

Hi, I currently have a transmitter supplying 4-20ma signal to a propotional valve that act as receiver. I would like to use IND.IO to filter the signal sent by transmitter. I wish to read the 4-20ma signal from transmitter for one minute and send the average value to receiver and I am thinking to use IND.IO as the processing bridge. However, per my understanding, this will require two isolated circuit between the analog input and analog output. I tried to measure continuity between the two common ports in the analogue section and found they are connected. Is it possible to do it?

Albert Tobing
Albert Tobing
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Asked on 10/9/16, 5:36 AM
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Hi Tom,

Thank you for your reply. I got it working already but the funny part is when I use: Indio.analogWriteMode(1, mA_p); and call: Indio.analogWrite(1, 100, false); in the loop, the output is only 10.7mA ( 42.5 % ). Isn't it suppose to output 20mA (100%)? I tried using: Indio.analogWriteMode(1, mA); and call: Indio.analogWrite(1, 20, false); I get 20.5 mA. I measure them using Sanwa PC-7000. The mA output mode is working correctly but not the mA_p. Anybody know what did I do wrong?

Albert Tobing
Albert Tobing
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Answered on 10/9/16, 2:45 PM
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Hi Albert, there seems to be a mistake in the Indio library for option mA_p, so i advise you to use the other modes mA and mA_raw. To get the most accurate results, you need to calibrate your IND.I/O as described here https://industruino.com/blog/our-news-1/post/ind-i-o-analog-calibration-18

Tom
on 10/11/16, 12:57 AM

Hi Albert,

You will use an Analog IN channel, and an Analog OUT channel, and indeed they share GND, so your transmitter and receiver will have a shared GND. The 2 circuits will have different signals based on your codel they do not need to be isolated for the purpose you descrived.

Tom
Tom
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Answered on 10/9/16, 11:00 AM
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Asked: 10/9/16, 5:36 AM
Seen: 728 times
Last updated: 10/9/16, 2:46 PM