DH Instruments PPC2+, Manual

Page: 50 / 166

PPC2+™ Operation and Maintenance Manual
©2001 DH Instruments, Inc.
Page 42
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PRINCIPLE
Leaks in the test system can have a detrimental effect on measurement accuracy and,
when large enough, can cause the PPC2+ to be unable to set and control
pressures reliably. The LEAK CHECK function is provided as a means of checking and
quantifying the leaks that may be present in the system.
PPC2+ is designed to precisely set, control and measure gas pressures.
Liquid contamination of the PPC2+ internal pneumatic control module and reference
pressure transducers can cause poor pressure control and interfere with accurate
pressure measurement. Liquid contaminants that may be present in test devices or
systems that are connected to the PPC2+ TEST port are likely to make their way back to
PPC2+’s internal pneumatic system as the test device or system is pressurized and
depressurized by PPC2+. To every extent possible, only clean hoses and connections
should be used in connecting PPC2+ to test devices or system and those devices and
systems should be free of liquid contaminants. However, in the event that PPC2+ will
need to be used to test some devices or systems that contain small amounts of liquid
contaminants, a Self Purging Liquid Trap (SPLT) accessory supported by the PURGE
function is available.
As the LEAK CHECK and PURGE functions are generally performed together at the
beginning of a test and there are commonalties to the procedures, PPC2+’s LEAK and
PURGE functions are designed to operate together under the single [LEAK CHECK]
function key.
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OPERATION
To access the LEAK CHECK/PURGE function, from the main run screen press the
[LEAK CHECK] function key. The function can be accessed directly at any pressure in
any range. The first screen is the leak check screen (see Section 3.2.8.2).
3.2.8.1 LEAK CHECK/PURGE MENU AND FUNCTIONS FLOW CHART
The flowchart of the LEAK CHECK/PURGE menu and functions is shown in
Figure 10.