I am new to analogue I/O's on PLC's. I have seen 4 to 20 mA inputs and the ladder programme that this represents (I think). The 4 ma is 3424 and the 20 mA is 16528 (IIRC) can check these numbers later. Can anyone tell me how we arrive at three thousand and odd and the sixteen thousand and odd. Is this some equivalent for the 4 to 20? What would this number be for say 12 mA? TIA
Allen Bradley SLC503 PLC Analogue
Sep 14, 2004
4 Replies
0-20 mA is 0-16383. That's why 4 ma is 3277. You can figure out what any point is along the scale since it is a linear relationship.
Thanks for that.
That's odd - I thought most AB SLC analog input modules were 14 bit resolution for current inputs . That is, they resolve 0-20 ma (range equals 20 ma) into
2^14 (16384) parts. Before any scaling, 0 ma should convert to the number 0 and 20 ma to the number 16383. Curious where the 16528 number came from?he is wrong about the numbers as I pointed out in a previous post, unless the thing is way off its calibration.
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