ADCS-601-AF™ OPERATION AND MAINTENANCE MANUAL
© 2005 - 2007 DH Instruments, a Fluke Company
Page 60
cylinder, 0.1 kg corresponds to increments of 1 kPa (0.3 inHg). When a pressure is
requested of the PG7601, it calculates the mass to load to reach the pressure. It then loads
the mass as closely as possible using its 0.1 kg resolution, calculates the actual pressure
achieved and displays that value. Therefore, when using the PG7601, the actual pressure
set may be up to 0.5 kPa (0.15 inHg) different from the pressure requested.
The FPG8601 pressure standard used to handle pressure requests under 15 kPa (4.5 inHg) (see
Section 2.2.2) is normally used in a similar manner. The FPG8601’s PPC3 pressure controller is
commanded to set and stabilize the requested pressure. Due to the possible difference between
the PPC3’s pressure transducer and the FPG8601, the final pressure set by the PPC3 will not be
exactly the requested pressure as read by the FPG8601. Since the FPG8601 is the pressure
standard and has much lower measurement uncertainty than the PPC3’s transducer, the
FPG8601’s reading is displayed as the ADCS-601-AF pressure value.
When using the FPG8601 (pressure points under 15 kPa (4.5 inHg), it is possible to set exactly
the requested pressure by using
Regulation
mode. In
Regulation
mode, the PPC3 pressure
target is iteratively adjusted by the difference between the PPC3 pressure transducer reading
and the FPG8601 reading to cause the FPG8601 to read the requested value of pressure within
the FPG8601 pressure hold limit. See Section 4.1.2.3 for information on pressure
Ready/Not
Ready
criteria when using FPG8601 with
Regulation
mode ON and OFF.
Regulation
mode
can be turned ON and OFF in the
ADCS Tools Run Screen Control Panel
when the FPG8601
is the active pressure standard (see Section 4.3.5.1).
4.1.5
ASOLUTE AND GAUGE MEASUREMENT MODES
ADCS-601-AF can operate in two measurement modes.
In
absolute mode
pressure is defined relative to a vacuum. Vacuum is provided by the
system reference vacuum pumps and is applied to the reference circuit of the pressure
standards (see Figure 29). The residual vacuum level is ready by thePG7601 and FPG8601
reference vacuum CDGs.
In
gauge mode
pressure is defined relative to atmosphere. The reference vacuum pumps
are turned OFF or isolated and the reference circuit of the pressure standards is opened to
atmosphere. The DUT may be connected to the reference circuit on the
TEST(-)
port to
assure that the DUT and pressure standards are at a common reference pressure.
See Section 4.2.3 for additional information on changing measurement modes.
There is a well defined order of operation for transitioning the ADCS-601-AF system
between measurement modes. The order is controlled by the ADCS Tools software. Mode
transitions should only be performed under ADCS Tools control. Vacuum pumps must
always be left ON in absolute mode. Before turning OFF vacuum pumps or disconnecting
vacuum supplies, transition to gauge mode. Once a measurement mode change is
initiated, it should be allowed to complete uninterrupted.
4.2
FREQUENTLY USED FUNCTIONS
Regular ADCS-601-AF operations relating to connecting and disconnecting devices under test and
setting pressures are performed from the
ADCS Tools
ADCS Run Screen
(see Section 4.3.5).
How to perform common ADCS-601-AF functions is summarized in Sections 4.2.1 to 4.2.8).
