Sensors enhance miniaturisation with vacuum measurement

30th July 2014
Staff Reporter

A line of MEMS Pirani Vacuum Sensors, targeted at HVAC and industrial applications, has been introduced by Posifa Microsystems. Designated the PVC 1000 family, the sensors enhance miniaturisation by employing a vacuum measurement solution which is based on the principle that the thermal conductivity of gases is proportional to pressure in the low vacuum range.

The sensors measure minute changes in resistance to a heated element, resulting from heat transfer to the surrounding gas. The heated element (measurement resistor) consists of a platinum thin-film resistor residing on a thermal insulating membrane. Ensuring precision measurement of heat transfer, the membrane is suspended over a micro-machined cavity that is 25μm in depth and has a bottom surface that is parallel to the membrane. Owing to the minute volume of the gas measured (the volume within the cavity), the sensors deliver ultra-low power consumption of < 5 mW and a fast response time  of < 5m Sec. With shock resistance to 1,000g, the PVC 1000 family is suitable for gas volume as low as 0.1 cm3.

The sensors have been designed for use in analytical instruments, leak detection in any closed system maintained under primary vacuum, vacuum packing machines, portable digital vacuum gauges, small mechanical systems (e.g. pumping) to achieve specified vacuum levels and low cost vacuum switches to verify vacuum from 10 millitorr to 30 torr.

Available in 4 lead TO-5 and 4 lead TO-46 metal can packages, the sensors often require unique packaging to accommodate the diverse applications into which they can be used. The company offers design services to customise the packaging, as the Pirani sensors often require unique packaging to accommodate the diverse applications into which they can be used. 




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