DH Instruments ADCS-601, Operation And Maintenance Manual

Page: 71 / 174

4. OPERATION
Page 59 © 2005 DH Instruments, Inc.
In normal operation, the ADCS Tools software that manages the ADCS-601 system,
determines which pressure standard system to use based on the pressure value to be set.
ADCS Tools also handles the transition from one standard to the other when the requested
pressure point requires changing the active pressure standard.
There is always an active pressure standard (see Table 11). Active is defined as connected
to the ADCS-601
TEST(+) port. Changing the active pressure standard requires changing
the states of the PG and FPG ISOLATION valves (valves 1 and 2) (see Figure 29) without
causing excessive perturbation to the pressure applied to the
TEST(+) port and the device
under test. This is accomplished by using the two PPC3 pressure controllers to set the same
pressure on either side of the isolation valve. Once this transition pressure has been set and
stabilized, the valves are operated. The default transition pressure is 15 kPa in absolute
mode and 14 kPa in gauge mode. The value can be changed in
ADCS Tools , [Setup] ,
[Configuration] , [Limits] but this is not recommended.
The transition between standards is initiated automatically when a pressure request is made
that requires the standard that is not currently active. A transition can also be initiated using
the
[Standard Transition] button on the ADCS Run Screen Toolbar (see Section 4.3.5.3).
Table 11 . Valve states
Valve states
(1 = open, 0 = closed)
Meas.
mode Active
standard
1 2 4 6 9 10 11
Reference
vacuum
pumps
PG7601 1 0 0 0 1 1 1 on
absolute
FPG8601 0 1 0 0 1 0 1 on
PG7601 1 0 1 1 1 1 1 off
gauge
FPG8601 0 1 1 1 1 0 1 off
Note: For valve references, see Figure 29, ADCS-601 simplified operational schematic.
Figure 29 . ADCS-601 simplified operational schematic