DH Instruments ADCS-601, Operation And Maintenance Manual

Page: 28 / 174

ADCS-601™ OPERATION AND MAINTENANCE MANUAL
© 2005 DH Instruments, Inc. Page 16
2.2 PRESSURE STANDARDS
2.2.1 PG7601 PISTON GAUGE
The heart of the ADCS-601 Air Data Calibration Standard is a PG7601 gas operated piston
gauge. The PG7601 piston gauge system includes:
- PG7601 piston gauge platform with terminal (on reference bench)
-
PC-7600/7100-10, TC 10 kPa/kg piston-cylinder module (mounted in platform)
- MS-AMH-38, 38 kg mass set (installed on platform)
-
AMH-38-VAC, automated mass handler (installed on platform)
- CDG-VAC-REF, capacitance diaphragm gauge with display and isolation valve for
measurement of PG7601 reference vacuum in absolute mode (installed on platform)
-
PPC3-700K pressure controller to automate PG7601 system pressure control (in
control cabinet).
The PG7601 piston gauge, AMH-38 automated mass handler and PPC3-pressure
controller are stand alone products for which separate Operation and Maintenance
manuals are available with much more complete information than is included in this
manual. Copies of these manuals are provided on the ADCS-601 Support CD and are
available at www.dhinstruments.com.
The PG7601 operates on the principle of the piston gauge in which pressure is defined by
balancing it against a known force on a known area (see Figure 11). The known area is
defined by a vertically mounted piston rotating in a cylinder and the known force is applied to
the piston by loading it with known mass subjected to acceleration due to gravity. When the
force applied by the pressure and the force applied by the mass accelerated by gravity are in
equilibrium, the piston floats and the pressure under the piston remains constant. The pressure
can be calculated following the equation in Figure 11. The pressurized fluid under the piston
also lubricates the gap between the piston and the cylinder. When floating, the piston must be
rotating to keep it well centered in the cylinder.
The PG7601 is equipped with a 10 kPa/kg piston-cylinder module and 38 kg mass set, giving
it a range of 10 to 380 kPa (3 to 120 inHg). The PG7601 Platform includes a bell jar that can
be evacuated with a vacuum pump so that pressure can be defined against vacuum
(absolute mode) or atmosphere (gauge mode). The AMH-38 mass handler allows the mass
load to be changed automatically. The PPC3 pressure controller adjusts pressure
automatically to float the piston (see Section 2.2.3).
Figure 11 . Piston gauge operating principle