Operation
58
GA10218_002_A7 - 9/2015 - © Oerlikon Leybold Vacuum
3.6.7 Background in standby
Main menu > View > Background in standby
The internal background leak rate can be displayed in standby mode or not.The
default setting is OFF.
The internal background is generated by residual gas (e. g. helium) that has not
been pumped away yet. Sources for residual gas are air or absorbed gases from
the inner surfaces of the PHOENIX L300i. This internal background will never dis-
appear totally. Very clean systems which have been pumped for a long time will
show a background in the 10
-11
mbar l/s range. Under normal conditions the
background level is in the 10
-10
mbar l/s or low 10
-9
mbar l/s range.
When pressing START the current internal background is subtracted from all fur-
ther measured signals automatically. Thus it is made sure that only the net leak rate
from the part under test is measured.
When switched to standby / Vent again a new internal background is calculated
after 25 s. The updated value is underlined. This means that if you press START
when the value is underlined, the actual background signal will be subtracted. If
you press START when the value is not underlined, the old background signal from
the last standby will be subtracted.
3.6.8 Lower Display Limit
Main menu > View > Lower display limit
This mode limits the lower detection limit of the measured leak rate. This is valid for
vacuum mode only.
Softkey 3: Off
The background leak rate will not be shown.
Softkey 5: ?
Help text.
Softkey 7: ON
The background leak rate will be shown.
Softkey 3, 7:
Changing of the lower detection limit between 1 · 10
-9
and 1 · 10
-12
mbarl/s.
The lower limit for the PHOENIX L300i DRY ranges between 1 · 10
-9
and
1 · 10
-11
mbarl/s.
Softkey 5:
?
Help text
