Dave M

I have a message box show when you press a button to turn on a heater saying " check pump" I don't want it to show up when you turn the heater off using the same button as a toggle. Is it possible? Or do I have to make two buttons "on" and "off" to make this work?

I still haven't sorted this out... How do I change the output of the PID block? Setting the high and low limits? Also, my control value seems to stay at zero regardless of the PV and setpoint. I have attached the program for your review. The issue is with the PID_Feedpump ladder. Thanks, Dave DM071521.ulpr

Is it as simple as "storing" the control value from the PID function to an analog output? Sincerely, Dave

Joe, Thanks for your reply! I have downloaded the example files. I have the USP-156-B10 PLC with analog input and output modules as well as transistor modules. I have successfully programed these units to use the PID function to control heaters with PWM using the transistor output. (like in the example files). I want to use the PID control to vary an analog (4-20mA) output as a signal to a VFD to control a pump. Regards, Dave

I am looking for an example program that controls an analog output with PID.