Pirani gauges are well known sensing principle for pressure below atmospheric. Our thermal conductivity chip is in fact also a miniature micro machined Pirani gauge, detecting easily low pressure as well as our intrusion of gas in air.
Air Pressure / Leak Detection / Intrusion
The atoms and molecules that make up the various layers in the Earth's atmosphere are always moving in random directions. Despite their tiny size, when they strike a surface they exert pressure. Each molecule exerts only a tiny bit of pressure. However, when the sum of all the pressures from a large number of molecules that strike a surface each moment is added, the total pressure can considerable. This is air pressure. As the density of the air increases, then the number of strikes per unit of time and area also increases.
Pressure, as in lots of situations, is relative. Air pressure has a tendency to equalize, Whether it is in a high-pressure machinery application, such as hydraulics, where high structural integrity is required to contain the material, or in a low pressure sealed unit application, such as a tamper proof load cell sealed with helium, the challenge is relatively speaking the same. It is also partially responsible for the phrase "nature abhors a vacuum," meaning a vacuum is hard to sustain under the pressure of Earth's atmosphere.
Atmospheric pressure varies slightly over the Earth's surface, and variations in pressure are responsible for the weather that we are so familiar with, for example high pressure areas have a tendency to seek out low pressure areas, causing gusts of wind.
In harnessing this natural phenomenon, NEROXIS offers unique low power MEMs-based technology to control and measure leaks and alarms for hermetically encased containers and spaces typically sealed with an inert gas. Typically, the Neroxis world of air pressure is in the 10-4 to 1 bar range.
MEMs-based Pirani principle
Combining a long established technology principle and recent advances in MEMS technology, a range of standardized and application specific miniature Pirani sensors is emerging from Neroxis. This technology, packaged in conventional electronic packaging, offers significant advantages in terms of pressure range, miniaturization and sensor combination, robustness and simplicity to be incorporated into equipment/process control systems, such as conventional piezoelectric silicon sensors. Due to the precise response to low pressure in the 0.1 to 10 tor range, miniature Pirani sensors facilitate innovative solutions in process industry applications for lower cost electronic pressure control systems.
