Selected Functions
5-24
Suggestions for Tuning Loops (continued)
5.11.4
T
able 5-3
shows symptoms, probable causes, and some corrective actions.
T
able 5-3
T
uning Loops
Symptom Probable Cause Remedy
Valve
command does not
follow the T
urboPlastic
output command
Incorrect zero span on
amplifier card
Zero span the valve
V
elocity setpoint too high,
causing output values to
exceed flow capacity of
valve
Lower the velocity setpoint
V
alve response too slow
T
ypical valve response should be
50 ms or faster
V
alve amplifier ramp
function on
T
urn off valve ramping function
Output causes excessive
overshoot and undershoot
T
oo much gain and/or reset
Lower gain and/or reset
Output is uniformly
straight and ignores all
setpoints
VSF too large for process Lower VSF
V
elocity setpoint too high
Lower velocity setpoint
No VSF is entered
Enter a VSF
Gain set too low
Increase gain
Output goes up/down
sharply causing jerky
motion
VSF too small for process
Increment VSF slowly (e.g., in steps
of +2) until motion is smooth
Not optimum algorithm
T
ry the other algorithm
T
oo much noise on input
Run RLL noise test and eliminate
noise source
A loop rate has been
entered
Delete loop rate
Module scan time too short
Increase the module scan time to
give better resolution on position
Loop response is not fast
enough
Not enough gain and/or
reset
Increase gain and/or reset
Currently used algorithm
not suitable for this process
Use the other algorithm and
observe results
Symptoms and
Actions
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