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TBV-OP-LIT 01/04
I
NTELLISYS
T
HROTTLING
B
UTTERFLY
V
ALVES
9
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TBV-OP-LIT 01/04
I
NTELLISYS
T
HROTTLING
B
UTTERFLY
V
ALVES
4.0 - Theory of Operation
The TBV-series valve is designed for downstream pressure control. 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 controller mod-
ule (APC, IQA or IQD) 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.
FIGURE 4.1 – TYPICAL INSTALLATION AND CONFIGURATION OF A TBV SERIES
CONTROL VALVE (DASHED LINES REPRESENT TBV-IQ SERIES INSTALLATION)
Initialization Sequence:
When first powered up, the TBV-series valve
will enter 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 may 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.
Vacuum Chamber
Pump
Host system with
RS232/485 or DeviceNet
communications
APC Controller
Throttle
Valve
Vacuum
gauge(s)
Normal Operation:
After the initialization sequence is complete normal
operation of the TBV control 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 a 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
and the throttle valve strives 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 APC, IQA
or IQD controller module so that the pressure set-point is maintained.
Tuning:
All Nor-Cal controller modules contain an Adaptive Pressure
Control Algorithm that has been designed to work over a wide range of
flow- and pressure-combinations. There are therefore no “learn modes” to
execute, nor does the user have 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.
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