SNAP PID MODULE REFERENCE
SNAP PID Module User’s Guide
21
Tune, IntegRatio
(also called the
Integral Ratio
)
(IntegRatio) This variable sets the integral value used
for the PID module’s PID calculations using the
following formula:
IntegRatio = Integral / Scantime
Enter the integral and scantime values you want to use
for your PID loop and then solve for IntegRatio. Enter
the result in the Tune, IntegRatio field in ioManager’s
PID Module window.
Range:
0.000 to 255.996
4.000
Manual or
Auto
Tune, DerivRatio
(also called the
Derivative Ratio
)
(DerivRatio) This variable sets the derivative value used
for the PID module’s PID loop calculations using the
following formula:
DerivRatio = Derivative / Scantime
Enter the derivative and scantime values you want to
use for your PID loop and then solve for DerivRatio.
Enter the result in the Tune, DerivRatio field in
ioManager’s PID Module window.
Range:
0.000 to 0.9992
0.000
Manual or
Auto
Filter Exponential
This variable sets the filter exponential used for the
Process filtering or Setpoint filtering equation using the
following formula:
where:
y
(t–0)
= raw input data
y
(t–0)
= current filtered answer
y
(t–1)
= last filtered answer
b = filter exponential
For
Process filtering,
the input to the filter is the raw
Process Variable. The output of this filter is used for the
Process Variable in the PID calculation.
Range:
0–255
For
Setpoint filtering,
the input to the filter is the raw
Setpoint value. The output of this filter is used for the
Setpoint value in the PID calculation.
Range:
0–255
0
(no filter)
0
(no filter)
Manual or
Auto
Manual or
Auto
Variable
Description
Default
To Modify,
Use Mode...
y
t 0
–
(
)
b y
t 1
–
(
)
×
1 b
–
(
)
y t 0
–
(
)
×
+
(
)
=
