Discharge-based pressure sensors for high-temperature applications using three-dimensional and planar microstructures

Two versions of microdischarge-based pressure sensors, which operate by measuring the change, with pressure, in the spatial current distribution of pulsed dc microdischarges, are reported. The inherently high temperatures of the ions and electrons in the microdischarges make these devices amenable to high-temperature operation. The first sensor type uses 3-D arrays of horizontal bulk metal electrodes embedded in quartz substrates with electrode diameters of 1-2 mm and 50-100-[micro]m interelectrode spacing. These devices were operated in nitrogen over a range of 10-2000 torr, at temperatures as high as 1000[degrees]C. The maximum measured sensitivity was 5420 ppm/torr at the low end of the dynamic range and 500 ppm/torr at the high end, while the temperature coefficient of sensitivity ranged from -925 to -550 ppm/K. Sensors of the second type use planar electrodes and have active areas as small as 0.13 [mm.sup.2]. These devices, when tested in a chemical sensing system flowing helium as a carrier gas, had a maximum sensitivity of 9800 ppm/torr, a dynamic range of 25-200 torr, and a temperature coefficient of sensitivity of approximately -1412 ppm/K. [2008-0262] Index Terms--Plasma applications, plasma confinement, plasma measurements, plasma properties, pressure effects, sensitivity.