62
Description of the Menu
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6.6.2.1
Background Suppression
•
>
>
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By this mode the internal helium background of the UL5000 will be subtracted at
every measurement after pressing START. This function helps to save clean up of
the UL5000 after a helium contamination.
6.6.2.2
Calculate Inlet Area Background
•
>
>
>
Calculate Inlet Area Background
This function calculates the value of the internal helium background that will be
subtracted from the measured signal when pressing START.
To start the calculation the UL5000 must be in the following state of condition:
•
)
•
Inlet port blanked off
•
UL5000 is in STAND-BY mode for at least 1 minute
•
UL5000 operates at least 20 minutes since powered on
The condition that is not yet fulfilled before doing the calculation will be back lighted
on the display. If all conditions are fulfilled “OK” shows up at the display and the
calculation can be started by pressing softkey no. 8. The procedure of the calculation
takes about 2 minutes, the status is displayed during the process. The helium back-
ground is indicated as the measured ion current in the mass spectrometer.
If the above perequisites are met, you can also calculate the inlet area background
by choosing the button CAL function.
Notice:
It is recommended to update the inlet area background calculation from
time to time because the UL5000 is pumping down an existing inlet area
background after a while.
Softkey 3:
Off
Background suppression is switched off
Softkey 6
Inlet area
In addition to the internal background subtraction the background from the
inlet port area will be subtracted at every measurement after pressing
START. When the function “Inlet Area” is selected, the value of the inlet port
area background can be determined before using the UL5000 for testing
(See Chapter
).
If the actual background is higher than 1×10
-8
mbar l/s the inlet area
suppression does not work. The high background must then be pumped
down.
Softkey 7
Internal only
The internal background (see Chapter
) will be calculated when swit-
ching to STAND-BY mode. This value will be subtracted when pressing
START.
