Technology - ThermoFisher Scientific GLD PRO Manuel D'utilisation

10.0 Technology

The leak detector measurement is based on thermal conductivity comparisons between
the probe air and a reference air. The device employs a dual thermistor technology that
measures the ratio of [probe]:[reference] heat exchange values and displays the results on
an LED scale (Figure 4). Under ideal operating conditions, a ratio of 1:1 indicates identical
air samples for both [probe] and [reference], and therefore, no leak is present.
LEFT: Dual analysis is achieved with
heater elements positioned in separate
flow chambers.
Because of slight differences in air temperature and/or humidity between the reference
inlet (Figure 1) and the probe tip, a small response indicated by a single red or yellow LED
light is generally insufficient to positively identify a gas leak. Small to moderate leaks are
reliably indicated with 3 red or 2 yellow LED lights and an intermittent beep. Larger leaks
are indicated with all red or yellow LED lights lit and a continuous audible alarm.
RIGHT: Probe and reference air streams
are simultaneously monitored for thermal
conductivity. Differences in air composition
are indicated by differences in the heater
element currents.
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