DH Instruments PPCK PLUS, Operation And Maintenance Manual

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PPCK+™ Operation and Maintenance Manual
©2001 DH Instruments, Inc .
Page 24
Dynamic Control
Dynamic control mode is designed to set the pressure to the target value and
control continuously to keep pressure within the hold limit, as close to the target
value as possible. The advantage of this
dynamic control mode is that the final
pressure achieved is the same as the target value. However, unlike static control, in
dynamic control a control error must be included in the uncertainty on the final
pressure applied. The maximum value of the control error is equal to the current
hold limit. The typical value of the control error is generally well inside the hold limit.
In dynamic control mode, test measurements are made when a Ready
condition occurs. Ready occurs when the set pressure is within the hold limit.
The reference pressure value applied to the test system is assumed to be equal to
the nominal pressure set value when
Ready occurs.
During dynamic pressure control, the hold limit is active. If the pressure goes outside
of the hold limit, a
Not Ready condition will occur (see Section 3.1.2.5). See
Sections 3.1.2.4 and 3.2.3 for default hold limit values. See Section 3.2.6 for setting
the hold limit to a user defined value. During active dynamic pressure control, the
stability limit is not used. The stability limit is used as the
Ready / Not Ready criterion
when control is suspended.
Figure 7. Dynamic Pressure Control Operation
Pressure Continuously
Adjusted to the Target Value
Time
Target Pressure
P
r
e
s
s
u
r
e