Inficon 540-200, Перевод оригинальной инструкции по эксплуатации

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6 | Operation INFICON
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Leak rate display of a
carrier gas
measurement
Fig. 21: Leak rate display of a carrier gas measurement with information on the helium
background of the sensor and the surroundings
The time required to achieve a constant signal in carrier gas mode (final value)
depends on the gas flow and the volume in the measurement chamber. The larger the
measurement chamber and the smaller the gas flow through it, the longer it takes for
the signal to reach its final value.
The time required to see 63 % of the signal is the volume of the measurement
chamber divided by the gas flow.
For example: For a volume of 2 liters and a gas flow of 20 l/s, 63 % of the signal can
be seen after 0.1 s. Three times this time reveals 95 % of the signal (0.3 s in this
example). Five times this time reveals 99 % of the signal (0.5 s in this example). With
a larger gas flow, the measurement is quicker but the sensitivity is lower. The smallest
representable leak rate increases with increases to the gas flow.
Dynamic measurement To save time, you can calibrate and measure with a shorter time than is necessary for
the leak rate final value. In this case, however, the temporal progression of every
measurement must be identical to the progression of the calibration. This method is
called dynamic measurement.
GROSS measurement
and FINE
measurement
The measurement cycle begins with a GROSS measurement. The FINE
measurement follows it automatically. For the GROSS measurement, the sensitivity is
limited to protect the sensor from helium contamination. The sensor measures with the
highest sensitivity for the FINE measurement.