Principle of the Wise Technology Sensor

Details to the basic principle of the Wise Technology sensor can be foimd in the 

In the classical mass-spectroscopic detection, the entirety of the gas molecules and atoms of to be analysed atmosphere is first ionised and accelerated. It is done under high vacuum conditions. The ions are separated according to their mass/charge ratio in the magnetic sector field and subsequently detected. 

The idea of the novel helium detection is a helium partial pressure sensor based on the known method of separating gases by a semipermeable membrane with gas-specific permeation. The component of the gas which is to be detected, in this case helium, is separated in the non-ionised state using the membrane. The amount of the separated helium is measured behind the membrane in a hermetically sealed volume, using a total pressure measurement in the evacuated volume. The change of total pressure in the enclosed volume corresponds to the helium partial pressure in front of the sensor membrane with a high selectivity for helium. 

Quartz is well permeable to helium. The selectivity of a pinhole-free, amorphous quartz membrane is very high for helium. Only hydrogen and neon show a significant permeation rate, but for this application this is negligible. In the enclosed volume behind the membrane the helium partial pressure rises to a pressure proportional to the partial pressure of the process side environment of the sensor. The total pressure of the external environment of the sensor system does not show any influence on the pressure inside the sensor volume. 

The permeability of quartz for helium, and therefore the sensitivity of the sensor depends on the temperature. For increasing the sensitivity and response time of the sensor, the quartz membrane is heated to about 350 C during operation of the sensor. 

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