An Experimental Frequency Response Characterization of MEMS Piezoresistive Pressure Transducers

Abstract

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.

Separated shear layer effect on shock-wave/turbulent-boundary-layer interaction unsteadiness

“…Based on assessments on the more widely validated XCQ-062 type transducers (e.g. Hurst et al 2014), and noting the cavity volume is nearly halved in this latest design, the resonance frequency is safely estimated at the upper end of the range, with no evidence of a signature noted within 0-50 kHz in the results -e.g. as established from the practically flat spectral levels prior to shear layer inception -and with a steep roll-off thereafter (55-70 kHz).…”

Numerical and experimental evaluation of shock dividers

“…The signal is filtered with a 50-Hz-150-kHz band-pass filter to remove noise. The delay of nearly 9 µs between the shock arrival and the plateau pressure corresponds to the rise time of the sensor [32,50]. The measured plateau pressure after the passage of the first shock wave is 8% less than the CFD predicted pressure.…”

“…A Kulite KSC-2 signal conditioner is used to amplify the measured signal. The relatively high resonance frequency of the sensor allows for a nearly non-oscillating signal behind the shock wave [29,32]. The probe is mounted at x/D = 12.5 inside the divider.…”

Water-Cooled Fast-Response Wall-Static Pressure Probes for Harsh Combustor Environment Applications

“…Since the presence of soot particles in the combustion chamber cannot be avoided, a solution is to further protect the fragile sensing element in addition to the use of a protective screened-recessed sensor layout. As recommended by Kulite [11], a layer of RTV coating has been applied on the restored sensing element (Figure 11 -bottom), shielding the fragile sensing element from external contaminants such as e.g. soot particles or even condensation droplets.…”