Allen-Bradley LOGIX 5000 Reference Manual page 94

Chapter 1 Process Control Instructions
Converting the PV and SP Values to Percent
The instruction converts PV and SP to a percent and calculates the error before
performing the PID control algorithm. The error is the difference between the PV
and SP values. When ControlAction is set, the values of EPercent, E, and
PVPIDPercent are negated before being used by the PID algorithm.
(1) PVPIDPercent and Deviation are internal parameters used by the PID control
algorithm.
Deviation High/Low Alarming
Deviation is the difference in value between the process variable (PV) and setpoint
(SP). Deviation alarming alerts the operator to a discrepancy between the process
variable and the setpoint value.
94 Rockwell Automation Publication 1756-RM006K-EN-P - November 2018