Model 979 Series Helium Mass Spectrometer Leak Detector
2-22
DRAFT 9/15/03
2.6.5.2 Selecting Fine Test or Gross Test Only Mode
Touch the USE FINE TEST (GROSS TEST ONLY) box to toggle the leak detector between a
fine test (normal) operating mode and a gross leak test only mode.
FINE TEST MODE
When USE FINE TEST (normal operating mode) is displayed, the
leak detector automatically tests for gross leaks and then transfers
into fine test if no gross leaks are detected.
GROSS TEST ONLY
When GROSS TEST ONLY is displayed (this feature is only avail-
able on dual mechanical pump configurations), the leak detector
does not transfer into FINE TEST mode. This feature is useful for
qualifying parts that have an unusually high rate of gross leak fail-
ures prior to fine leak testing.
2.6.5.3 System Sensitivity
Table 2-5 and Table 2-6 show sensitivity matrixes for performing Fine and Gross tests using
standard and high sensitivity configurations.
High Sensitivity
System
The High Sensitivity 979 system can achieve 10
−
10
atm cc/sec
(5E-11 MDL) sensitivity. This sensitivity can be achieved at a
transfer pressure of 100 mTorr. High ambient helium background
conditions may prevent 10
−
10
atm cc/sec testing at relatively
high pressures. The maximum detectable leak capability in the
CONTRA-FLOW mode for single rough/forepump configurations
is 9.9 x 10
−
5
atmc/sec (full-scale reading on 10
−
5
range).
Standard Sensitivity
System
The Standard Sensitivity 979 System can achieve 10
−
9
atm cc/sec
(5E-10 MDL) sensitivity. This sensitivity can be achieved at a
transfer pressure of 100 mTorr. High ambient helium background
conditions may prevent 10
−
9
atm cc/sec testing at relatively
high pressures. The maximum detectable leak capability in the
CONTRA-FLOW mode for single rough/forepump configurations
is 9.9 x 10
−
4
atm cc/sec (full-scale reading on 10
−
4
range).
Summary of Contents for 979 Series
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