I am controlling temperature with a PID instruction in RSLogix 5000. There is a selection for PV tracking. I have been unable to get an answer from their tech support on what this actual does. Does anyone have any experience with using PV tracking and can explain the details behind this function?

 

It means that when you choose to activate it, the setpoint will be the same as the Process Variable. It is usually used in bumpless control on which when a control is set from auto to manual, the setpoint will take the value of the PV as long as it is in manual mode. When the control mode is reset to auto mode, the setpoint will take the last PV value before it was reset to auto. This ensures that there will be no/lesser impact on the final control element upon switching modes.
You might want to incorporate it in your mode selector of the controller.

 

PV Tracking is An option on many controllers. When a control loop is in MANUAL, with PV Tracking turned on, the controller setpoint (SP) will follow the PV. When the loop is returned to AUTO, there is no sudden movement of the process, because the PV is already at setpoint. If PV Tracking is turned off, returning to AUTO will drive the loop to its previous setpoint.

For a more complete glossary of process control terms, click
here: http://www.expertune.com/r2.asp?f=AList&t=glossary&l=glossary.html

 

PV Tracking forces the SP to equal the PV while in manual mode. The idea is that the operator is manually modifying the CV to force the PV to a desired value, so it would be nice if the SP tracked that PV value such that when the operator returned the loop to auto, it would control at that value forced by the operator.

 

As the other posters said, it sets the SP to the PV value on change from Manual to Auto. AKA "Bumpless Transfer". Most controllers have this feature. The disadvantage is you then have to adjust the setpoint to where you want it.

Roy

 

Yes indeed, it is for bumpless transfer from manual mode to auto mode. Additional advantage is absence of nuisance alarms like "Deviation" alarm, which appears if there is some predetermined difference between setpoint and process value.

One more advantage lies in the configuration of adaptive PID controller and characterizer functions. If you need your controller to follow some proportional curve based on signal characterizer and need this feature to be absent during manual mode, you select PV Tracking.

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