Model 979 Series Helium Mass Spectrometer Leak Detector
DRAFT 9/15/03
2-27
GROSS LEAK XFER
The GROSS LEAK XFER set point determines the test pressure cross
over point at which the 979 transfers into the GROSS LEAK TEST
mode from Roughing mode. In the GROSS LEAK TEST mode, the
majority of the sampled gas is pumped away through the dedicated
roughing pump while a small sample of gas is introduced into the
leak detector through a throttle valve. Gross leak testing is a stan-
dard feature available on dual mechanical pump configurations
only.
CONTRA-FLOW LEAK
XFER
The CONTRA-FLOW LEAK XFER set point determines the test
pressure cross over point at which the 979 transfers into the
CONTRA-FLOW LEAK test mode from Roughing mode or
Gross Leak Test mode. In the CONTRA-FLOW LEAK test mode, the
gas sample is pumped through the leak detector and swept across
the high vacuum pump foreline. The CONTRA-FLOW LEAK test
mode allows for relatively high sensitivity testing at exceptionally
high test pressures.
2.6.8 NEXT and BACK Boxes
Touch the NEXT box on the First Menu screen to display the Second Menu selection screen.
The operations of the Second Menu screen are discussed in Section 2.7 “Second Menu
Selection Screen”. Touch the BACK box to return to the Home screen.
Summary of Contents for 979 Series
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