Cutler-Hammer D320 PLC, User Manual

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SETPOINT The desired value for the Process Value (PV).
PROCESS VALUE The actual value of the input that control is being performed on. In most
applications, this will be an analog value that is desired to be at a certain
level (SP), such as a water level, temperature, flow rate, etc.
CONTROL VALUE The automatically or manually calculated value of the PID loop used to
adjust the PV. This is normally tied to an analog or digital output such as a
valve, solenoid, etc.
CONTROL VALUE The maximum allowable value for CV.
MAXIMUM
CONTROL VALUE The minimum allowable value for CV.
MINIMUM
PROPORTIONAL The proportional term of the PID loop equation.
INTEGRAL The integral term of the PID loop equation.
DERIVATIVE The derivative term of the PID loop equation.
FEEDFORWARD A bias term applied as an offset to the PID loop equation.
SAMPLING TIME The amount of time between taking samples of the PV. At this time, a PV
is taken, and a new CV is calculated. The D320 then waits for this amount
of time before performing the next calculation.
DEADBAND The acceptable amount of error between the PV and SP. When the error is
less than or equal to this amount, no additional adjustment is performed to
the CV.
MANUAL CV SETTING The value to set the CV to when the PID loop is set to Manual Mode (PID
Loop Control Bit 2 – see Table 2 above).
MAXIMUM SCALING The maximum process value that will be seen. Setting this value allows
VALUE the PID loop to calculate the full range of CV based on a limited input
range. The PV and CV are scaled to reflect the scaling ranges set.
MINIMUM SCALING The minimum process value that will be seen. Used with the above
VALUE parameter to scale the PV and CV for maximum effectiveness.
The remaining parameters of the PID loop parameter block are used by the D320 for calculation of the
PID loop equation. These values are carried over from calculation to calculation, and must not be
modified by the user program.