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Help - Basic Fan Control PID Loop

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Hi All, 


I'm new to the PID/Autotune function and am having some issues getting a closed feedback loop up and running. 


To simplify my problem, I have a V130-J-TR6 with an IO-AI4-AO2 expansion module. I have a fan that is driven by a 0-10V analog analog output, and a duct setup to measure airflow using a pressure transducer with 4-20mA analog signal (Kimo CP201).


The fan is connected to the 12Bit expansion module. The transducer is connected to an analog input on the PLC so it is 10-bit.


From the sensor display I know the following:


1.2V ----> 0L/s (the fan doesn't cut in until voltage exceeds at least 1.2V)

10V----> 250L/s


What I want to do is maintain a constant flow-rate of 175L/s but I don't completely understand how to set autotune up or what it's doing.


Can someone please provide me some example ladder logic or .vlp file. I have tried using the v120 example in the help files with no luck. Surely this is a common application. All my equipment is new and I've run diagnostics with the multimeter so I know its not a hardware issue.





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  • MVP 2023

And I have to ask what is the make and type of fan?  I assume that the 201 is hooked into a pitot differential flow sensor or similar.  I ask about the fan model because many modern variable rate fan systems have onboard functions to vary their rates directly from a sensor.  It is often easier to get the fan to do it itself, and just have the plc monitor things, as the manufacturer has already done the complex maths to suit that particular model.  Your setup looks small, so consider that you may be adding unnecessary complexity.


Some fans also have inbuilt pitots which make things much easier as well.  It is all to do with exactly what looks like your scenario....same flow rate regardless of pressures, filters getting dirty, etc. I only use the plc as the controller when there are a host of other factors involved in varying the flow rates, and these are on much larger installations than yours.





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