Models 947, 948 and 960 Leak Detectors Operations and Service Manual
3-7
TEST TIME
The TEST TIME variable determines the amount of time that the
leak detector remains in test before it compares the measured leak
rate with the selected reject set point. Sufficient time must be
allowed for the leak rate reading to stabilize before the system
makes a pass/fail decision. This is a function of the part configura-
tion and the leak rate specification. In AUTO SEQUENCER mode,
the 947/948/960 remains in test for the entire duration of the prese-
lected test time.
FINE TEST MODE
When FINE TEST (normal operating mode) is used, the leak detec-
tor automatically tests for gross leaks and then transfers into fine
test if no gross leaks are detected.
GROSS TEST ONLY
(HOLDING IN GROSS
FOR LARGE LEAKS)
The 947/948/960 Leak Detector uses the Contra-Flow system,
which has a gross leak manifold, allowing testing at higher inlet
pressure with reduced sensitivity.
When TRANSFER TO FINE TEST is set to NO, 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.
TRANSFER POINTS
Set the test transfer pressures for each testing mode.
The transfer pressure settings can be adjusted to lower values for
specific applications. The 947/948/960 has pre-programmed upper
transfer pressure limits that are slightly greater than the default set-
tings. These limits prevent the operator from inadvertently setting
the 947/948/960 to transfer into test at too high a pressure, resulting
in excessive spectrometer tube contamination or ion source fila-
ment failure.
GROSS LEAK XFER
The GROSS LEAK XFER set point determines the test pressure cross
over point at which the 947/948/960 transfers into the GROSS
LEAK TEST 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 detec-
tor through a throttle valve.
Summary of Contents for 948
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