User guide

AccuMeter Controller Chapter 11: Configuring a new PLC 77
PID SETUP Tab
• PID UPDATE TIME. This is the rate at which the PID will make corrections to the
target blend rate to attempt to maintain the weight at the median point between the
RELOAD % (Hopper Setup Tab) and the HOPPER SIZE value (Hopper Setup Tab).
Setting this value smaller will allow the blender to react quicker to changes in the bulk
density of the material. Setting it too low will cause the control to become under
damped and out of control. This condition is obvious because the blender will appear
to chase up and down and will never settle into a target. Making the value too large
will cause the blender to hit high level or reload and will prevent it from staying
between these values. This condition is also obvious because the blender will not stay
running, but will not be showing “FIXED RATE” indication on the main page. Default
is 5 and should not be changed without consulting ACS service or engineering.
• PID GAIN. This is the gain value that affects the proportional error correction
characteristic of the PID. Setting this too large will cause a condition similar to setting
the PID UPDATE TIME too low and will cause it to become under damped. Setting it
too low will cause a condition similar to setting the PID UPDATE TIME too high.
This value primarily effects how large of a correction is made that is proportional to the
current error. Default is 15 and should not be changed without consulting ACS service
or engineering.
• PID INTEGRAL CONSTANT. This is the multiplier for the integral error correction
characteristic of the PID. This setting reacts the same as the PID GAIN setting.
However, this correction is not related to the current error, but is dependent on the total
for the last several errors. Default is 10 and should not be changed without consulting
ACS service or engineering.
• INITIAL RATE. Each time that the blender fills the mass flow hopper up it shuts off
and settles for 5 seconds and then will not turn back on until the mass flow weight
reaches the top of the upper steady window. At that time the Initial Rate is locked in
and this is the value that the PID starts with. It quickly makes a correction to reach the
median. If the INITIAL RATE is far from what the actual extrusion rate is then the
Mass Flow hopper is out of calibration or being interfered mechanically.