Inficon Pernicka 700H CHLD, Translation Of The Original Operating Instructions

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Accumulation
Accumulation is a phase during the measuring procedure. Tracer gas escaping from
the test object is accumulated in the closed measuring system. The change in the
tracer gas quantity over time serves to determine the leak rate.
Internal helium background
The measurement system of the leak detector also contains a residual amount of
helium. This generates an internal measurement signal component (background
signal), which superimposes on the leak display.
So that this background signal can be suppressed, an internal "background
suppression" can be activated with the factory settings.
Minimum detectable leak rate
The minimum detectable leak rate which can be detected by the leak detector under
ideal conditions (> 4 x 10
-14
mbar l/s).
Background signal
Helium or hydrogen (as part of water) are natural components of air.
Before any leak detection, an amount of the adjusted tracer gas is already in the
volume on the surfaces of the test chamber, supply lines, and even in the leak
detector itself. This certain amount of tracer gas generates a measurement signal
which is called the "Background signal". The ongoing evacuation of the test chamber
continuously reduces this background signal.
Foreline pressure
Pressure of the backing pressure between the turbo molecular pump and the backing
pump.