Nor-Cal Intellisys Adaptive Pressure Controllers - Manual (Page 14)

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I
ntellIsys
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dAptIve
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ressure
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ontrollers
APC-OP-LIT 1/12
Initialization Sequence
When first powered up, the APC controller will run the valve through an
initialization sequence that lasts for approximately 30 seconds. The primary
purpose for this operation is for the controller to determine the fully open
and closed points, as well as for certain motor and position calibration steps
to occur. While the initialization sequence is active, the amber FAULT light will
be illuminated and the OPEN/CLOSE LEDs will blink in an alternating fashion.
Once the initialization sequence is complete, the valve will move to the fully
open position and the green OPEN LED will illuminate.
NOTE: The controllers for TPV pendulum valves and TSS
gate valves contain a valve initialization safety lock function.
This safety lock will prevent valve initialization to occur until
given a “clear-to-proceed” command. The RS-232 serial
command for this is JC. Alternatively, the \Valve Initialization
Enable In\ TTL pin can be pulled low to initiate this sequence.
CAUTION: Never attempt to initialize a throttle valve with
differential pressure across the sealing gate. Make sure the
pressure on both sides is equalized. Damage to pumps and
other equipment can occur otherwise.
4.0 - Theory of Operation
All APC controllers are designed for downstream pressure control (see Fig 4.1 and 4.2). As such, it is one of four important components in a pressure
control system. The other three essential components include a host system computer, a throttle valve and one or two vacuum gauges, such as a
Capacitance Diaphragm Gauge (CDG). Most manufacturers’ vacuum gauges can be used to provide the vacuum measurement signal, provided
they have a voltage output proportional to pressure.
Vacuum Chamber
Pump
DC power supply
Host system with
RS232/485 or DeviceNet
communications
Nor-Cal
IQ-series
Valve
Vacuum
gauge(s)
FIGURE 4.1 – TyPICAL INSTALLATION AND CONFIGURATION OF A bURIED
bOX INTELLISyS DOWNSTREAm PRESSURE CONTROL SySTEm
FIGURE 4.2 – TyPICAL INSTALLATION AND CONFIGURATION
OF AN Iq PRESSURE CONTROL VALVE
Vacuum Chamber
Pump
AC or DC power supply
Host system with
RS232/485 or DeviceNet
communications
APC Controller Nor-Cal
throttle
valve
Vacuum
gauge(s)
Normal Operation
After the initialization sequence is complete normal operation of the valve is
possible. There are two primary modes of operation, a) position control mode
and b) pressure control mode.
In
position control mode , the valve will move to any position in its range
based on a position set-point command from the host. The valve will remain
in that position until instructed to do otherwise. Position control mode can
be useful in certain cases where pre-determined amount of baffling or
throttling is necessary.
Pressure control mode , on the other hand, is used whenever control to a
specific system pressure level is desired. The host provides the set-point value
to the controller which, in turn, moves the valve to achieve that set point as
quickly as possible. During pressure control mode, external perturbations
such as flow changes and plasma events will automatically be compensated
for by the controller so that the pressure set-point is maintained. The set
point value can be changed by the host at any time.
Tuning
The APC controller contains an Adaptive Pressure Control Algorithm that
has been designed to work over a wide range of flow and pressure combina-
tions. The APC controller therefore does not have a “learn mode” and there
is no need for the user to set PID parameters. In some instances, however,
vacuum system design may affect the closed loop pressure control time
constants. As a result, pressure control performance may at times be
affected. If satisfactory pressure control cannot be achieved with the
Adaptive Pressure Control Algorithm, please contact Nor-Cal Products’
Intellisys Customer Support.