Series 65 INSTALLATION
963283EA Edition 2019-05-03 49/
4.9 Learn (adaptive control algorithm)
LEARN adapts the PID controller of the valve to the vacuum system and its operating conditions. LEARN
must be executed only once during system setup. The LEARN routine determines the characteristic of the
vacuum system. Based on this, the PID controller is able to run fast and accurate pressure control cycles.
This characteristic depends on various parameters such as chamber volume, conductance and flow
regime. Therefore it must be performed with a specific gas flow according to instruction below.
The result of LEARN is a pressure versus valve position data table. This table is used to adapt the PID
parameters. The data table is stored in the device memory which is power fail save. The data table can
be up-/downloaded via ‘Control Performance Analyzer’ software or remote interface. Due to encoding the
data may not be interpreted directly.
By an OPEN VALVE, CLOSE VALVE, POSITION CONTROL or PRESSURE CONTROL command the
routine will be interrupted.
Parameter Description
Select one of four learn bank to place the result of the learn procedure.
Important: It’s important that after the learn pressure controller select this
Set learn limit pressure (to which pressure the learn shall be executed).
The value is related to the sensor full scale of high sensor.
1.0 means the whole pressure range of the sensors
Define the speed for opening the valve during the learn procedure.
1.0 means full speed
State of the current learn
0:Not Started
1:In Progress
2:Completed Successfully
3:Aborted
4:Failed
Warning of current learn procedure:
Bit 0: Learn is running
Bit 1: Checksum error (learn data corrupt)
Bit 2: Learn procedure terminated by user
Bit 3: Pressure at position open > 50% of pressure limit
Bit 4: Pressure at minimal conductance position < 10 % of pressure limit
Bit 5: Pressure falls while move valve in direction of close
Bit 6: Pressure at open position does not match pressure of previous open
Bit 7: Learn procedure terminated by program
Bit 8: Pressure <= 0 at open position (no gas flow set?)
Parameter location:
CPA RS232
Pressure Control->Adaptive Learn Refer to “RS232 setup commands” for details.
Execute a learn procedure:
1. Set specific gas flow according to calculation below and wait until flow is stable. Learn does not
need to be performed with the process gas. Instead N
2
or Ar may be used.
2. Set parameter Bank Selection, if only one learn is used take Bank 1. Be sure that the pressure
controller also selects this learn bank!
3. Set parameter Open Speed. If it’s critical for the chamber, if the pressure falls rapidly while
opening the valve, reduce the open speed.
4. Set parameter Controller Mode = LEARN.
5. Wait till Controller Mode leave to LEARN state Learn procedure is finished
6. Check if the learn was successful by checking if Status shows value 2 (=Completed
Successfully). In best case Warning Info shows no warning.
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