3. OPERATION
Page 45 © 2002-2007 DH Instruments, a Fluke Company
The internal volume of the SPLT is about 20 cc. The SPLT will not operate effectively
if the volume of liquid contaminants collected is greater than about 10 cc. The SPLT
is designed to protect the PPC3 only against residual liquid contamination. Even if
an SPLT is being used, precautions should be taken to reduce potential liquid
contamination from the device or system under test as much as possible before
making the connection to the PPC3 TEST(+) port.
Do not plug the SPLT exhaust valve. The purge routine can not be completed with the
SPLT exhaust valve plugged and the SPLT’s protective function will not be effective.
If the SPLT is electrically connected to the PPC3, its exhaust valve will always be open
when the PPC3 vent valve is open. If desired, it may be closed manually using the
DRIVER function (see Section 3.4.7).
3.3.9 [LEAK CK]
PURPOSE
To run an automated leak check routine that determines the leak rate of the system
connected to the PPC3 TEST(+) port.
PRINCIPLE
Leaks in the system connected to PPC3’s TEST(+) port can cause differences between the
pressure measured by the PPC3 Q-RPTs and pressure in other parts of the test system.
A large leak can cause the PPC3 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.
The principle of the LEAK CHECK function is the measurement of the natural decrease or
increase of pressure in a fixed volume over time. The LEAK CHECK function allows a leak
check time to be set. The total pressure change and the average rate of change over the
leak check time are calculated and displayed.
Changing the pressure in a test system causes adiabatic temperature changes in the gas
that need to have dissipated before a valid leak measurement can be made.
In general, a 30 second to 1 minute wait before running a leak check is adequate to allow
the adiabatic temperature change to dissipate and valid leak measurements to be made.
However, stabilization time may be much longer with liquid test media, as volumes
increase and as pressures increase.
OPERATION
To run a leak check, first set the pressure to the desired leak check pressure using the direct
pressure control keys (see Section 3.1.3) or automated pressure control (see Section 3.3.10).
Changing the pressure in the test system causes adiabatic temperature changes in the
gas that need to have dissipated before a valid leak measurement can be made.
Generally, a 30 second to 1 minute wait, depending on the magnitude of the pressure
change and the size of the total pressurized volume, is adequate.
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