Silicon micro-machined piezoresistive based pressure transducers are often used to make high frequency dynamic pressure measurements. The spectral or frequency response of these microelectromechanical systems (MEMS) is a function of the natural resonance of the sensor structure, sensor size, sensor packaging, signal conditioning and transducer mounting in the desired measurement location. The advancement of MEMS micro-fabrication, which has reduced sensor size dramatically, and the high elastic modulus of silicon have allowed the natural resonance of these devices to range from 100kHz to several MHz [1]. As a result, packaging and mounting at the point of measurement are the major factors that determine the flat (0dB) frequency response envelope of the transducer, which is typically quantified by a transfer function. The transfer function quantifies the difference both in magnitude and phase between an input signal and a measured signal in the frequency domain. The dynamic response of pressure transducers has historically been estimated via a unit step input in pressure created through a shock tube test that excites the high natural resonance of the chip. Unfortunately, these tests are less effective at accurately quantifying the frequency response of the transducer in the domain of greatest interest (DC-20kHz), specifically the bandwidth over which the response is flat (0dB). In this work, we present a test methodology using a speaker-driven dynamic pressure calibration setup for experimentally determining the transfer function of a pressure transducer from 1–50kHz. The test setup is validated using capacitive-based microphones with claimed flat spectral characteristics well beyond 50kHz. Using this test setup, we present experimental spectral response results for low-pressure miniature MEMS piezoresistive pressure transducers over the frequency range of 1–50kHz and qualitatively compare these results to traditional shock tube tests. The transducers characterized have been manufactured with several different standard sizes and front-end configurations.

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The push to advance the performance and longevity of gas turbine engines requires better characterization of flow instabilities within the compressor and most importantly the combustor. Detecting the earliest onset of these flow instabilities can help engineers either manipulate the flow to restabilize it or make informed design changes to the engine. The pressures within gas turbine engines are typically composed of an undesired, low-level oscillatory pressure of less than 1kPa to several kPa superimposed on top of a large, relatively constant pressure of several thousand kPa [1–7]. The high-pressure transducers used to measure the pressures within these environments are often unable to resolve these low-level oscillatory pressures that characterize the flow instabilities because the signal output for such pressures is often the same level as the noise within the sensor-data acquisition system. This paper presents an engine test ready, high temperature, combined static and dynamic pressure transducer that uses static pressure compensation in order to measure these low-level dynamic pressures with an excellent signal to noise ratio and, at the same time, captures the overall static pressure within a gas turbine [8–10]. Test bench experiments demonstrate the static-dynamic transducer’s unique ability to capture both large static or quasi-static pressures of 1,380kPa or greater and simultaneously measure the acoustic-level dynamic pressures superimposed on top of these pressures. The static-dynamic transducer achieves this advanced sensitivity through the use of a low-pass acoustic filter that passes the large static pressure to the reference port of a high sensitivity dynamic pressure sensor within the transducer such that the overall static pressures cancel out and the sensor measures all acoustic-level dynamic pressures. These bench tests additionally demonstrate the transducer’s ability to operate reliably when exposed to the harsh, high temperature environment (up to 500°C) within a gas turbine [8–10].