A 14.39ppm/kPa Stress Sensor with Low Temperature-drift and High Linearity for turbulence Stress

In the analysis and calculation of turbulent flow, the stress generated by the fluid needs to be accurately measured by sensors. In this research, a mechanical stress sensor was developed based on standard 180nm CMOS technology for real-time measurement of stress. The main contributions of this study include the following: 1) The temperature-compensated RC oscillator circuit changes mechanical stress-induced chip deformation into a frequency output. When the temperature was changed from -40°C to 120°C, the oscillator frequency only changed to 0.303Hz/ °C. 2) No complicated calibration and complicated measurement equipment are required. The chip area does not exceed 0.569 mm². Moreover, the power consumption does not exceed 22.9 µW. 3) The average sensitivity measured by the chip is 14.39ppm/kPa, and the linear fitting curve's determination coefficient (R2) is 0.9983.

I. Introduction

Stress measurements in turbulent boundary layers are very important for fluid mechanics. Due to their large available bandwidth and small spatial size, MEMS sensors are often used for fundamental research on turbulence, flow control feedback, and aerodynamic drag measurements, as well as for validating computational turbulence models [1]. Currently, the commonly used floating element sensors have fluid damping and heat transfer problems to thermal sensors, making it difficult to accurately predict the frequency response function [2]. In order to improve the measurement accuracy, MEMs sensors with small size and high-temperature stability can be used. The integrated capacitive stress sensor manufactured using the standard CMOS and microelectromechanical system (MEMS) technology has been applied in pressure sensors in [3]. Piezoresistive stress sensors result in resistance changes due to the piezoresistive effect that can be measured [4]. This paper developed a mechanical stress sensor based on 180nm CMOS technology for real-time stress measuring. A sensor circuit with on-chip integration is used in order to reduce parasitic capacitance. This sensor has a good frequency and temperature stability, small area, low noise, and good linearity within the measurable pressure range. Fig. 1.

Schematic of plane-wave tube device used for stress measuring in air turbulence models.

Fig. 2.

Architecture of the stress sensor integrated with the rc oscillator converting the stress to a frequency.