Edwards ELD500 Series

D135-10-880C - Operation
Page 55
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
ELD500. This internal background will never disappear 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 further
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
seconds. The updated value is underlined. This means that if START is pressed when the value
is underlined, the actual background signal will be subtracted. If START is pressed when the
value is not underlined, the old background signal from the last standby will be subtracted.
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 x 10
-9
and 1 x 10
-12
mbar l/s.
The lower limit for the ELD500 DRY ranges between 1 x 10
-9
and 1 x 10
-11
mbar l/s.
Softkey 5: ?
Help text