Using the Data Watch Window
202 372 SPU 780 01EMAN May 2002
PID TunerPID and PID2
Blocks Overview PID and PID2 blocks are software programming blocks that allow a process tobe
controlled with no changes or additions to hardware. "PID" stands for "Proporti on al
Integral Derivative". While the PID2 is a more advanced version of the PID, both
operate in the same manner.
PID/PID2 Process
The PID calculation compares a process variable (PV) with a desired control point
called the set point (SP). The calculation uses the difference between the set point
and the process variable to adjust the P ID output value (OV), sometimes called th e
control variable. This output value is used to manipulate an input to the process so
that, eventually, the measured process variable equals the desired set point.
PID Tuner
Overview The PID summary displays a list of all the PID and PID2 instructions in the logic of
the current project. Each row in the grid gives the instruction name, its location in
logic, and the addresses of key data values related to that PID block.
The currently selected row has an associated PID Faceplate. This faceplate allows
simple tuning of the selected PID block. You may invoke manual mode or adjust the
setpoint value.
Process Output
Process
Process Input
PID
Calculation Output Value (OP)
Measurement
Set Point (SP)
Process Variable
(PV)
Note: There may be a delay while a search is performed for PID instructions in
logic.