Wireless micromachined ceramic pressure sensor for high-temperature applications

Abstract

In high-temperature applications, such as pressure sensing in turbine engines and compressors, high-temperature materials and data retrieval methods are required. The microelectronics packaging infrastructure provides high-temperature ceramic materials, fabrication tools, and well-developed processing techniques that have the potential for applicability in high-temperature sensing. Based on this infrastructure, a completely passive ceramic pressure sensor that uses a wireless telemetry scheme has been developed. The passive nature of the telemetry removes the need for electronics, power supplies, or contacts to withstand the high-temperature environment. The sensor contains a passive LC resonator comprised of a movable diaphragm capacitor and a fixed inductor, thereby causing the sensor resonant frequency to be pressure-dependent. Data is retrieved with an external loop antenna. The sensor has been fabricated and characterized and was compared with an electromechanical model. It was operated up to 400 C in a pressure range from 0 to 7 Bar. The average sensitivity and accuracy of three typical sensors are: 141 kHz Bar 1 and 24 mbar, respectively.

Continuous wireless pressure monitoring and mapping with ultra-small passive sensors for health monitoring and critical care

“…However, with all the sensors operating below a few hundred MHz, none has been able to miniaturize below a few mm 3 in volume [3][4][5][6][7][8][9][10][22][23][24][25][26] . Traditional passive strategies have been inherently limited by the self-resonant frequency of readout circuitry because interference effects make it difficult to detect sensors operating near and above this frequency [27][28][29] .…”

Inductive Telemetric Measurement Systems for Remote Sensing

“…The frequency at the phase minimum (f min ) is related by f 0 from the expression (14), which corresponds to the Taylor expansion of f min in k (coupling coefficient) and Q -1 (quality factor of the sensing circuit) (Fonseca et al, 2002).…”

“…In (Fonseca et al, 2002), the telemetric system is used to monitor the pressure inside high temperature environments. In (Hamici et al, 1996), an example in the field of biomedical applications for the monitoring of internal package humidity for either in vitro or in vivo testing is described.…”

A novel readout system for wireless passive pressure sensors

“…Inductor and cavity (LC) resonant sensors can represent valid solutions since they do not require a wiring liking and power supply. The sensors are composed of a capacitance cavity which is sensitive to the external pressure and a planar spiral inductor which is connected to the capacitance to form an LC resonant circuit, and they have been widely used in many applications [1][2][3][4].…”