PLC 5 PID question - MAX Scaled Input

skyfox

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I am trying to figure out how to calculate the 'UNSCALED" Setpoint value based on operator entered PID setpoint. Not sure I have all the terminology correct. Read thru the PID instructions but still a bit confused.

Input to the PID Process Varibale (PV) is 0-4095 (Instrument range = 0 to 150psi)

What should I used for " MAX Scaled INPUT" Parameter? Better yet, where do I find what I need to enter in to this register? In other words, what determines this MAX scaled input value?

What is the unscaled Setpoint value? is this an user entered parameter or PID instruction generated value?

Thanks.
 
The actual math depends on your input card raw signals.

Use the whole range of 0-4095 (unless you wish to use and have a CPU that supports a floating point PID).

Figure out the slope and offset to get that from your input card values, and apply the math just before you execute the PID.

The intstruction set reference will give you the mechanics, search for post by Ron Beaufort with BOTH PLC5, and PID for laymans terms applications and fantastic explanations.
 

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