3. OPERATION
Page 37 © 1998 DH Instruments, Inc.
3.2.8.1 LEAK CHECK/PURGE MENU AND FUNCTIONS FLOW CHART
The flow chart of the LEAK CHECK/PURGE menu and functions is:
3.2.8.2 LEAK CHECK SCREEN FUNCTION
The leak check screen appears when the PURGE/LEAK CHECK function key
has been pressed from the main run screen.
1. Current measured pressure and pressure
units.
2. Active reference pressure transducer and
range.
3. Current rate of change of pressure (leak rate)
in current pressure units/second.
4. Current rate of change of pressure (leak rate)
in current pressure units/minute (updated
every 10 seconds).
998.36 psi a H3
0.001/s 0.06/m
This screen is for observing the current leak rate. Pressing ESCAPE returns to
the main run screen.
Pressing VENT when in the leak check screen causes the PURGE function to
execute (see Section 3.2.8.3).
Pressing ENTER when in the leak check screen goes to the set pressure screen
(see Sections 3.2.3.1 and 3.2.8.4).
In general, the maximum acceptable leak rate for optimal PPC2 AF
automated pressure control operation and to assure in tolerance
measurements is ± 0.02 psi (140 Pa)/second or 1.2 psi (8.3 kPa/minute)
when using range 1, 2 or 3 of the Hi reference pressure transducer and 0.001
psi (7 Pa)/second or 0.06 psi (420 Pa)/minute when using range 1, 2 or 3 of
the Lo reference pressure transducer.
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. In general, a 0.5 to 1 minute wait, depending on
the magnitude of the pressure change and the size of the total pressurized
volume, is adequate to allow the adiabatic temperature change to dissipate
and valid leak measurements to be made.
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