Agilent Technologies VS Series Operation Manual page 88

VS Series Helium Mass Spectrometer Leak Detectors
Auto-Zero < 0 Inactive When Auto-Zero < 0 is inactive, the leak detector does not
Split Flow
Gross Test
3-4
automatically adjust the zero reference point when the helium
background level drops below the previously set zero reference
point. In this condition, a leak less than the previously set zero
value is not indicated by the system. Instead, the arrows remain lit,
indicating that the background level is below the previously set
zero reference point. Press Zero on the front panel to readjust the
zero reference point manually. This clears the lights.
For High Pressure Test/Sniffing mode, de-activation (Inactive
NOTE
AZ<0) is highly recommended. Manual Zeroing produces a
more desirable performance, thus eliminating false leaks due to
fluctuations in test port pressure while in test.
Activating the split flow option properly characterizes the system to
an external calibrated leak, which is influenced by additional vac-
uum pumping sources. These separate vacuum pumping sources
reduce the amount of helium measured by the leak detector.
The split flow option is very useful for external calibrations were
external gain factors exceed the limit of 50 due to a high helium
background (Range Stop E-8). The split flow factor is also useful for
calibrating to a standard leak while in the sniffing mode
(High Pressure Test).
Allows the operator to locate leaks while the system is in roughing
mode. The test indicates the presence of a leak at high pressures
only and does not display a leak rate value.
Gross Test is activated in the ADVANCED PARAMETER
❑
menu.
Once activated, the GROSS TEST button appears on the
❑
Home screen. Press GROSS TEST to enter the screen.
There is an audio tone for Gross Leak testing, which
❑
increases as the leak increases.
Gross Test only works when the test port pressure is between
❑
10 and 150 Torr and remains constant (± 2% between
previous and current pressure readings).
The Gross Leak test stops if the system goes into Backing,
❑
Test or Fine TEST mode.
Activating the Auto Sequencer button terminates the Gross
❑
Leak test.
The HOLD button is inactive while in Gross Leak test mode,
❑
as the system is in roughing mode.