What is PV tracking or Setpoint tracking?

There are two types of operational modes in controllers:

Manual mode:  the controller output (M), is specified by the process operator, control calculations are not performed, and no value is required for MR.

Automatic mode: the controller output (M), is computed based on the PID control equation; these computations require a value for MR

What is PV tracking or setpoint tracking?

PV Tracking is a multi-controller alternative. The controller setpoint (SP) will follow the PV when a control loop is in MANUAL, with PV Tracking turned on. There is no sudden motion of the method when the loop is returned to AUTO, as the PV is already at setpoint. Returning to AUTO will drive the loop to its prior setpoint if PV Tracking is switched off.

Setpoint tracking relates to the controller setpoint being automatically adjusted to follow the process variable (PV). This happens when the controller is in manual mode (only if the option is activated).

If set point tracking is enabled, the transfer will take place without any change in controller output when the controller is moved to auto.

The simpler computation, with PV tracking enabled, led to its use within pneumatic and electronic analog controls. For digital controls, the additional calculations for PV tracking disabled are trivial, so most allow PV tracking to be enabled or disabled on an individual loop basis.

When a controller is switched to auto, the operator is responsible for providing a proper value for the setpoint. How this is done depends on whether PV tracking is enabled or disabled

MR,0= M0- Kc E0

PV tracking enabled: The operator cannot change the setpoint while the controller is in manual. The operator must first switch the controller to auto, and then enter the value for the setpoint.

PV tracking disabled: The value of the setpoint is used to compute the initial control error, E0, which is then used to calculate MR,0. The operator must first enter the value for the setpoint, and then switch the controller to auto.

Some advanced control configurations require PV tracking to be enabled or disabled. But for most loops, the decision to enable or disable is largely personal preference.