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python01

PID operation without PID or PIDAT instruction?

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Is it possible to run some sort of PID operation on OMRON PLC without PID or PIDAT instruction? I need to modify a program and although it seems that they use PID loop to control temperature I can not find PID or PIDAT instruction anywhere in the whole program. Can they put the instruction somewhere where the find function would not see it? Also what is this instruction --|| |--? I looked through the instruction manual but did not see one like that in there so what is it?

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Which version of Omron PLC??? Try working backwards from the output. I have seen things like SCL functions used to control analog outputs. If it's a TC module they are probably using the internal temperature control PID in the module. That instruction looks like an immediate refresh. Right clck on the contact and see what is selected in the options list.

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judging by the symbol of contact in ladder, it is diffup contact and the plc is probably some CQM1. There you cannot check diffup option directly on contact properties but you have to use DIFU(13) instruction on some other bit which you then use for diffup functionality and it has a symbol like one you posted. We must know for sure which plc is used. At CQM1H there is PID instruction but you should first insert it in expansion instruction table. complicated days back then... Edited by tashinz

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tas is correct. That is a contact from a DIFU instruction somewhere else in the program. Tell us what I/O modules you have in your stack.

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CQM1, CPM2, C200H... Yes, expansion instructions was a PITA!

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