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Flow Rate Calculation
309738L
105
Volume Compensation
Volume compensation is used when the PrecisionFlo LT
system is operated in bead control mode. The system
measures the actual flow rate and adjusts the pres-
sure/flow relationship (as determined during flow cali-
bration) to achieve the desired flow.
When flow calibration is completed, the resulting pres-
sure value is divided by 100 to obtain a 1% value. The
initial offset is set to 0%, the initial peak is set to 100%
(see Flow Calibration on page 104).
Each time a new flow rate measurement has been com-
pleted, the actual flow rate is compared to the requested
flow rate. The flow rate command from the automation
unit (analog or fixed) is also compared to the flow rate
defined by the flow comp pivot point value. The pivot
point should be set to the average value of the minimum
and maximum automation commands when using Ana-
log for automation mode.
The volume compensation routine moves the end points
of a straight line which defines the pressure/flow rela-
tionship of the system.
The end point of the pressure/flow line (offset or peak) is
moved the 1% value determined at the end of the flow
calibration routine. The magnitude of the flow rate error
does not affect the size of the adjustment.
The maximum adjustment range of the peak point is
25% to 400% of the original value from calibration. If the
25% or 400% limits are reached, a Volume Comp Limit
fault is generated.
Endpoint
Adjustment
Flow Command <
Flow comp Pivot
Point
Flow Command >
Flow comp Pivot
Point
Flow rate <
desired
flow rate
Increase offset
Increase peak
Flow rate >
desired
flow rate
Decrease offset
Decrease peak