TECHNICAL INFORMATION
14
87-900-120-01 (A)
Theory of operation
The system to be tested is filled with a mixture of
helium/air.
The probe is passed over areas considered to be
critical and, via a sampling pump, the mix of gases
around the areas examined is sampled and piped
towards the internal sensor.
The sensor consists of a pressure detector and of a
heated quartz capillary which is highly permeable to the
molecules of helium, while permeability for all other
atmospheric gases is negligible.
High Voltage Supply
Helium
Detector
Heater
Exhaust
gas
Sniffing
gas
Probe
Sampling Pump
Current Amplifier
Display
Keyboard
MICROPROCESSOR
Theory of operation
While the atmospheric gases are vented to the outside,
the molecules of helium reach the pressure detector.
The electric signal proportional to the partial pressure
of the helium taken from the detector, is processed by
the microprocessor of the central unit. This permits
direct readout of the concentration of helium on the
display (ref. figure below).
