Installation, Operating & Maintenance Instructions
Series 615 DN 40 (I.D. 1½”), DeviceNet
VAT Vakuumventile AG, CH-9469 Haag, Switzerland
Tel +41 81 771 61 61 Fax +41 81 771 48 30 CH@vatvalve.com www.vatvalve.com
3.11.3 Tuning of control performance with soft pump algorithm
3.11.3.1 Optimizing P gain
This valve may be used to control pressure ramps during pump down. The P parameter of the pressure controller requires
correct adjustment. This parameter must be set once during system setup and is stored in the device memory which is
power fail save. Based on the soft pump controller configuration, the valve is able to run fast and accurate pressure control
cycles. The P parameter can be evaluated using below instruction.
Introduction
Soft pump control mode allows a completely user-defined pressure profile, usually from atmosphere down to some process
pressure
1. Optimizing P gain
The P gain value evaluated for soft pump control mode might be different than the P gain value evaluated for PI controller
mode. When switching to soft pump control mode the P gain value evaluated fort he PI controller has to be send to the
valve controller. When switching back into PI controller mode the respective P gain value has to be send again.
Adaptive pressure control mode ignores any P gain value.
1.1 Basic settings
The pump down characteristic is determined by start pressure, end pressure and pump down time. This straight line from
start pressure to end pressure.
The VAT soft pump controller requires a pump down time shorter than 10 sec. for good control results. If the required pump
down time is longer than 10 sec., the pump down curve has to be partitioned into sections shorter than 10 sec. with
corresponding end pressure.
Example:
Start pressure: 760 Torr
End pressure: 10 Torr
Pump down time: 30 sec.
Here the pump down time and the corresponding pressure is being divided into three sections. The host sends a new
pressure set point every 10 sec.:
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