Chapter Four: Operation How To Use the Bias Control
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How To Use the Bias Control
The BIAS control establishes a floor, or minimum, signal level to the valve which prevents the
integrator from “winding up” or going too far into saturation. The signal to the valve consists of
the bias level plus the controller signal. In MANUAL, the controller signal is determined by the
MANUAL control. In AUTO, the controller signal is determined by the error signal and the
GAIN and PHASE LEAD controls.
For good control, it is important that the BIAS be set as high as possible, particularly during
pressure transients. The factory BIAS adjustment is for 35% of output.
If the controller cannot turn the valve completely off, the BIAS may be set too high. If the BIAS
control needs adjustment, do the following:
1. Turn the MANUAL control to zero.
2. Turn the CMAE switch to CLOSE and check that there is no flow and the system can be
pumped to zero pressure.
3. Turn the CMAE switch to MANUAL; there should still be no flow.
4. If there is flow, turn the BIAS control counterclockwise (CCW) until the flow stops and
then two more turns CCW.
5. If there is no flow, turn the BIAS control clockwise (CW) until flow just appears and
then back off (CCW) two turns.
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