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Auto zero:
Zeros sensor before testing to remove ambient pressure/ force changes
that may affect the test.
Fill/Evac 1:
Evacuates the chamber of air to a controlled pre-set limit; which
allows the positive pressure inside the pack to inflate the pack, creating the force
onto the load cell, and a pressure differential between the inside of the pack and
its outside. The lower the pre-set pressure, the greater pressure differential is
inside and outside the pack. Depending on the pack’s construction, a large
pressure difference can cause the pack to burst/split/open.
Fill/Evac 2:
A second Fill/Evac step. (Normally not used in this configuration.)
Isolate:
A half second step to allow time for valves to operate before proceeding.
Stabilize:
Allows the pack to stabilize. After the pack inflates, it takes a period of
time to settle into its inflated position; packs don’t inflate uniformly. While the
pack is stabilizing, the force on the load cell varies as it settles into its inflated
shape. If the stabilization step is too short, it could lead to false failures of good
packs.
Measure:
Measures the different in force between the start of the measure step
and the end of the measure step. If the force decay is larger than the limit, the
pack will be rejected. If the force decay is less than the limit, the pack will pass.
The limit should be the maximum limit the pack is allowed to decay over the test
time. This is normally worked out by testing packs with known leaks and setting
the limits around the results.
Exhaust:
Vents the chamber back to atmospheric pressure. Note the lid cannot be
opened until the exhaust step is completed.
