INFICON Composer Gas Concentration Controller - Manual (Page 86)

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Composer Operating Manual
The response of a system with too little controller gain (its PROCESS GAIN
value is too large) is characterized as over damped as shown in
Figure 3-10 .
Decrease the PROCESS GAIN value until the system oscillates as is shown by
the under damped curve. Proper control is established by an intermediate value
that approximates the critically damped curve.
Figure 3-10 Examples of Damped Curves
3.2.1.3 Typical Parameter Values
Some values that have performed well in our delivery system are: PROCESS
GAIN = 0.95, TIME CONSTANT = 23 sec., and DEAD TIME = 8 sec. The
parameter values computed by ITAE Criteria were tried and then somewhat
optimized by increasing the DEAD TIME slightly as shown in
Figure 3-10 . A
longer DEAD TIME makes for a very slow response.
3.2.1.4 Setting Total Flow
When SW#5 on CFGR2 is set, the CONCENTRATION OUTput is used as a
slaved controller output. Specifically, it is used to maintain CHANNEL FLOW as
(Total Flow minus Bubbler Flow) equals Dilution Flow. Refer to
section 1.10.4.3,
How to Connect the Instrument for Independent Control of the Concentration,
on page 1-20
for further descriptions.