Discharge-Based Pressure Sensors for High-Temperature Applications Using Three-Dimensional and Planar Microstructures

Abstract

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-μm interelectrode spacing. These devices were operated in nitrogen over a range of 10-2000 torr, at temperatures as high as 1000 • 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 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.

Ultrawide‐Bandgap Semiconductors: Research Opportunities and Challenges

“…Complementing electric-current-based transduction, charged particles generated by field emission and field ionization on ultra-sharp semiconductor tips or filaments can be superior transducers for fast, efficient and reliable sensing of gas, pressure, shock and vibration in extreme conditions. [323] Beyond the integrated sensing/electronics system itself, power delivery to the system is also an important challenge. Present battery technology is limited to an operational temperature below 150 °C, and cabled-power wiring dramatically increases system weight and complexity making it impractical for many harsh environments.…”

“…By employing recent advances in low‐dimensional materials synthesis, multiple analytes and physical state variables can be detected in an orthogonal fashion. Complementing electric‐current‐based transduction, charged particles generated by field emission and field ionization on ultra‐sharp semiconductor tips or filaments can be superior transducers for fast, efficient and reliable sensing of gas, pressure, shock and vibration in extreme conditions …”

A Microdischarge-Based Monolithic Pressure Sensor

“…For the conditions encountered in these devices, ions have temperatures moderately above ambient with transport coefficients that are also not particularly sensitive to high operating temperatures. Microdischarge-based pressure sensors have been operated as high as 1000°C [3]. Other pressure sensors for high temperature utilize Fabry-Perot and other interferometers [1], and piezoresistors in high band gap materials such as SiC (up to 600°C) [31] and even Si (up to 600°C) [32].…”

“…Pressure and vacuum sensors based on this method of transduction utilize the change in plasma distribution within a cavity that may be caused either by a change in the plasma pressure [3] or by the deflection of a plasma electrode under external pressure [4]. Sensitivity levels in the range of 40,000-75,000 ppm/kPa have been reported [3], which are comparable to piezoresistive pressure sensors. However, as in capacitive pressure sensors, linearity is compromised.…”

A high voltage generator utilizing a single PZT element with series-connected electrodes

“…Miniaturized HV sources that scavenge ambient mechanical energy are of particular interest for microdischarge-based sensors in long term and self-powered integrated microsensing systems. A variety of sensors based on microdischarges, like radiation detector, pressure sensor in harsh environment, chemical sensor for gas chromatography etc., have been reported [5][6][7][8][9][10]. In those applications, the threshold voltages to initiate discharges are typically between 500 V to 1 kV.…”