404 PID Function Block SxPID1i

PID Function Block SxPID1i

Here are descriptions of the inputs to the SxPID1r function block used in Tracker IPm. Most of the inputs and output for this function are real (floating point) values except for the Mode input, which is an analog value (whole number).

INPUT VARIABLE
NAME TYPE DESCRIPTION, Units
auto BOOLEAN When FALSE, the PID functions in Manual Mode. The PID output pid_calc will follow the value of the input manual_level. (See manual_level below.)
When TRUE, the PID functions in Automatic Mode. The PID output pid_calc will be determined by previous data and the other PID function inputs.
Value = 0 or 1, FALSE or TRUE
Refer to the SXPID1r Application Notes in Toolkit Help for in-depth descriptions of these two modes.
pv REAL This is the process variable from the controlled process. The PID calculates its current error by subtracting setpoint from this pv input.
Example: 350.3
setpoint REAL This is the targeted output value. The PID calculates its current error by subtracting this setpoint from the pv input.
Example: 347.55
Pgain REAL This value represents a proportional constant. Pgain determines how the PID’s error (pvsetpoint) and other influences (integral and/or derivative terms) affect the calculation of the PID output. The higher Pgain is, the more effect the error will have on the PID output.
Example: 25.56
Igain REAL This value represents the integral time constant. Igain affects the amount of influence the PID’s internal integral term has on the calculation of the PID output. An Igain setting of 0.0 effectively eliminates all influence of the integral term. The higher Igain is, the more effect the integral term will have on the PID output.
Example: 1.375
Dgain REAL This value represents the derivative time constant. Dgain affects the amount of influence the PID’s internal derivative term has on the calculation of the PID output. A Dgain setting of 0.0 eliminates all influence of the derivative term. The higher Dgain is, the more influence the derivative term will have on the PID output.
Example: 0.70
time REAL This is the loop update time, in seconds. If the PID’s calculated delay is less than time, the function will not make any adjustments to the PID output. The minimum time is 0.1 seconds (100 mS). All times less than this are rounded up to 100 mS.
Example: 1.0
mode ANALOG When 0 (zero), the PID functions in Position Forward Mode. The PID output varies in direct relation to the pv. An increase in the output causes an increase in the pv. Most applications use this mode.
When 1 (one), the PID functions in Position Reverse Mode. The PID output varies in direct relation to the pv. An increase in the output causes a decrease in the pv.
When 2 (two), the PID functions in Velocity Forward Mode. The PID output is the rate of change of the loop calculation. An increase in the output causes an increase in the pv.
When 3 (three), the PID functions in Velocity Reverse Mode. The PID output is the rate of change of the loop calculation. An increase in the output causes a decrease in the pv.
Refer to the SXPID1r Application Notes in Toolkit Help for in-depth descriptions of these modes.
Value = 0 to 3
manual_level REAL In Manual Mode, the PID output is set to this value. (Manual Mode is invoked by setting the auto input to 0 (zero).)
Example: 13570.0
bias REAL This bias value is added to the PID output in Manual and Automatic modes.
Example: 3500.0
deadband REAL This value specifies the minimum amount of error (process variable minus setpoint) required for the PID output to be recalculated. deadband eliminates output dither due to small input fluctuations. This input applies to Automatic mode only.
Example: 250.0
max_change REAL This value specifies the maximum amount the PID output is allowed to change with each output update. max_change provides slew rate limiting. This input applies to Automatic mode only.
Example: 1000.0
max_out REAL This value specifies the maximum allowable PID output, in Automatic and Manual modes.
Example: 32767.0
min_out REAL This value specifies the minimum allowable PID output, in Automatic and Manual modes.
Example: 0.0

 

 

Here is a description of the output of the SXPID1r function block.

 

OUTPUT OUTPUT
NAME TYPE DESCRIPTION
pid_calc REAL This is the last calculated output of the SxPID1r function block.
Example: 13507.55