A-B PID instruction

tkhawkin · Jul 7, 2010

Hi, I am controling water temperture using an thermocouple card to a PID then to a analog output card. The problem I have is the valve ma signal is in the wrong direction. I am using a PLC5/40 processor. What is the best way to change this.

Ron Beaufort · Jul 7, 2010

try changing the "Control Mode" or "Error" setting ...

E = SP - PV goes one way ...
E = PV - SP goes the other ...

and welcome to the forum ...

if you have other questions, please tell us what platform you're using ... not all Allen-Bradley PIDs are the same ...

tkhawkin · Jul 7, 2010

The control mode did not work, so I will try changing error.
Thanks

Ron Beaufort · Jul 7, 2010

please tell us what platform you're using ... not all Allen-Bradley PIDs are the same ...

some platforms call the setting ONE thing ... other platforms call it ANOTHER thing ...

TConnolly · Jul 7, 2010

Are you cooling or heating?

You can also try reversing your scaling so that 4mA = High_Process_Variable and 20mA = Low_Process_Variable.

Which analog card are you using?

tkhawkin · Jul 11, 2010

After changing the error to PV and sp-pv to pv-sp this did work.

Thankyou very much

tkhawkin · Jul 11, 2010

Thanks I got it.

A-B PID instruction

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