PV Switching

PV Switching allows the 9220 to use two (2) analog inputs as a process variable source, if necessary.  It can be customized in any combination of high or low signals for loops 1 or 2.  The 9220 controller normally only uses loop 1 for temperature control, so PID loop 2 must be modified so that it has a control source.  In order for the PV signal to be switched, both PV signals must be above or below the switch point and must satisfy any applicable hysteresis.

 

PV Switch Active Loop

This field is not modifiable.  It will display the current active loop (Loop 1 – Loop 2).

 

PV Switch Action

This switches the active control loop based on the current PV, PV Switch Value, and PV Switch Hysteresis. For an example, assume the PV Switch Action is Loop 1 low, Loop 2 high. Now assume that the PV Switch Value is 1400 and the PV Switch Hysteresis is 50. In this situation, Loop 1 will be used as the control loop until both Loop 1 and Loop 2 PVs are higher than 1400, at which point it will switch to Loop 2 for the control loop. The control loop will continue to be Loop 2 until both PVs fall below 1350 (Switch Value – Hysteresis), at which point control will switch to Loop 1.

 

PV Switch Value

This is the switch value.  This is the value that will determine when the switch happens.  The range is -300 – 30000.

 

PV Switch Hysteresis

This is the hysteresis for the switch.  This will help prevent the 9220 from potentially switching back and forth between the two signals.  The range is 0 – 30000.