User guide

AccuMeter Controller Chapter 11: Configuring a new PLC 70
FIFO SETUP Tab
• SAMPLE SIZE IN %. This is the percent of hopper that is sampled for the data point
entered into the FIFO. Making this number smaller makes the system respond more
quickly. Making this number too small will induce unwanted error in the algorithm.
Making this number larger will delay the samples and dampen the controller.
• NUMBER OF POINTS IN FIFO. This is the number of samples that will be analyzed
by the FIFO algorithm to determine if the feeder’s weight loss is steady. Decreasing
this number will make the system respond more quickly, but too small may cause
erratic behavior. Making this number larger will sample more points and will dampen
the controller.
• ALLOWABLE % DIFFERENCE FOR STEADY. Once the FIFO has been filled to
the NUMBER OF POINTS IN FIFO then the % difference is calculated based on this
FIFO. If the calculated % difference is less than the ALLOWABLE % DIFFERENCE
FOR STEADY then a Steady Flag is given for the feeder. Making this number larger
will allow the system to respond to larger errors. Making it too large will cause erratic
behavior. Making it too small will cause the system to become volumetric ignoring the
load cell weight loss information and will then control the motor strictly based on the
entered MEASURED FEED FACTOR (Calibrate Feeder Tab).
• MAX ALLOWED FEED FACTOR. If the instant sample and motor speed calculate a
Feed Factor that is larger than this value then a “0” is entered into the FIFO for that
sample. This value should be set to a value that is 2-3 times the MEASURED FEED
FACTOR (Calibrate Feeder Tab) after the blender has ran for some time. Setting this
prevents the operator from causing problems by draining the hopper out the drain shoot
while the motor and blender are running. The rate through the drain tube is remarkably
steady.
• NOTE ON THE FIFO SETUP. The FIFO is a well tested algorithm that has been used
by ACS for many years. Before modifying any of these parameters it is recommended
that you talk to an ACS service or engineer. Setting these values inappropriately can
cause significant errors in accuracy. Set correctly the FIFO algorithm makes your
system impervious to operator interference caused by touching the weigh hopper and
vibration.