3. OPERATION
Page 33 © 1998 DH Instruments, Inc.
3.2.6 CUSTOM CONTROL
PURPOSE
To customize the control parameters of the current automated control mode for the current range.
PRINCIPLE
Automated pressure control and the associated pressure ready/not ready condition are
characterized by hold limit and stability limit parameters.(see Sections 3.1.2.3 and 3.1.2.4) which
determine how PPC2 AF will control and under what conditions a "ready" indication will occur.
PPC2 AF provides system default values for the hold limit and stability limit parameters which
have been determined to be those most suitable for the typical user to operate within
PPC2 AF pressure control and measurement specifications. The default parameters are
automatically set when the control mode is selected using the CONTROL function key (see
SYSTEM DEFAULT CONTROL PARAMETERS below).
The CUSTOM CONTROL function allows the hold and stability limit parameters to be
adjusted by the user. This can be used to increase control speed (time to "ready"), which
usually decreases precision, or to increase precision which usually decreases control speed
(see Section 3.1.2.4). For example, changing the dynamic pressure control hold limit in range
3 of the Hi reference pressure transducer from ± 0.02 psi to ± 0.1 psi will decrease the time it
takes to set a pressure since the limit in which the pressure must be set has increased by a
factor of five but it will also increase by a factor of five the possible control error included when
ready is indicated.
Adjusting default control parameters using the CUSTOM CONTROL function may result in
control parameters that the PPC2 AF is unable to meet so that a "ready" condition never
occurs. This does not indicate PPC2 AF malfunction, just that the control parameters
need to be relaxed or set back to default parameters.
SYSTEM DEFAULT CONTROL PARAMETERS
Lo Reference Transducer
Range 1, 2, 3
Hi Reference Transducer
Range 1, 2, 3
Hold Limit Stability Limit Hold Limit Stability Limit
Static
Mode
± 1 % of F.S. of the
active pressure
measurement range
± 0.005 % of F.S./sec
of the active pressure
measurement range.
± 1 % of F.S. of the
active pressure
measurement range
± 0.005 % of F.S./sec
of the active pressure
measurement range.
Dynamic
Mode
± 0.0025 psi
(35 Pa )
± 0.0025 psi
(35 Pa)/sec
± 0.05 psi
(350 Pa
)
± 0.05 psi
(350 Pa )/sec
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