User manual

IEC61131 User and Reference Manual
April 22, 2008
324
pida
Analog Output PID Function Block
Description
The pida function block performs a PID algorithm and calculates an analog output.
In automatic mode, the output is calculated using the PID algorithm. A new calculation is
done at the rate specified by cycleTime.
In manual mode (auto = FALSE), the output is set to the value of the outManual input. The
output is limited to the range set by full and zero.
If the cycleTime parameter is less than the cycle time of the ISaGRAF application program,
the sampling period is the period of the application.
The analog output function block pida appears as follows.
pv
sp
gain
reset
rate
deadband
full
zero
cycleTime
auto
outManual
out
pida
Arguments
Inputs
Type
Description
pv
Real
The process value is used to calculate the process error in the
PID algorithm. error = pv – sp
sp
Real
The setpoint value is used to calculate the process error in the
PID algorithm. error = pv – sp.
gain
Real
The proportional gain. A positive value of gain configures a
forward-acting PID controller and a negative value of gain
configures a reverse acting controller.
reset
Real
The reset time, in seconds. This controls the reset gain (or
magnitude of integral action) in a PI or PID controller. Valid
range is any value greater than 0. A value of 0 disables the
reset action.
rate
Real
The rate time, in seconds. This controls the rate gain (or
magnitude of derivative action) in a PD or PID controller. Valid
range is any value greater than 0. A value of 0 disables the
rate action.