Silicon Piezoresistive Pressure Sensor Research Articles

Temperature Compensation Method Based on Bilinear Interpolation for Downhole High-Temperature Pressure Sensors.

Due to their high accuracy, excellent stability, minor size, and low cost, silicon piezoresistive pressure sensors are used to monitor downhole pressure under high-temperature, high-pressure conditions. However, due to silicon's temperature sensitivity, high and very varied downhole temperatures cause a significant bias in pressure measurement by the pressure sensor. The temperature coefficients differ from manufacturer to manufacturer and even vary from batch to batch within the same manufacturer. To ensure high accuracy and long-term stability for downhole pressure monitoring at high temperatures, this study proposes a temperature compensation method based on bilinear interpolation for piezoresistive pressure sensors under downhole high-temperature and high-pressure environments. A number of calibrations were performed with high-temperature co-calibration equipment to obtain the individual temperature characteristics of each sensor. Through the calibration, it was found that the output of the tested pressure measurement system is positively linear with pressure at the same temperatures and nearly negatively linear with temperature at the same pressures, which serves as the bias correction for the subsequent bilinear interpolation temperature compensation method. Based on this result, after least squares fitting and interpolating, a bilinear interpolation approach was introduced to compensate for temperature-induced pressure bias, which is easier to implement in a microcontroller (MCU). The test results show that the proposed method significantly improves the overall measurement accuracy of the tested sensor from 21.2% F.S. to 0.1% F.S. In addition, it reduces the MCU computational complexity of the compensation model, meeting the high accuracy demand for downhole pressure monitoring at high temperatures and pressures.

Thermal Compensation System for Silicon Piezoresistive Pressure Sensors Based on Surface Fitting and Wild Horse Algorithm

Thermal Compensation System for Silicon Piezoresistive Pressure Sensors Based on Surface Fitting and Wild Horse Algorithm

Optimization of linearity of piezoresistive pressure sensor based on pade approximation

To optimize nonlinearity and temperature drift of silicon piezoresistive pressure sensor, novel calibration algorithm based on Pade approximation is adopted in the paper. The output data of the pressure sensor is processed by the novel algorithm to remove the influences of the cross-sensitivity and the unexpected jump points. High accuracy up to 0.01% FS can be achieved based on the algorithm. Compared with the other published algorithms, the proposed algorithm shows the merits of high accuracy, less memory consumption, and low cost. The algorithm can have potential application in the field of the intelligent sensor with the requirement of high output accuracy.

Research on temperature drift mechanism and compensation method of silicon piezoresistive pressure sensors

Silicon piezoresistive pressure sensors have played a key role in the detection field due to their small size, high sensitivity, and high integration. However, the factors such as its material particularity, the temperature dependence of the piezoresistive coefficient, the variation of carrier motion in the material caused by heat-induced stress, doping concentration, and resistance mismatch may cause the sensor to generate temperature drift. In this paper, the mechanism of temperature drift of silicon-based pressure sensor is analyzed initially, and then a comparison between BP neural network and wavelet neural network is done, which shows the root mean square error of the wavelet neural network is much smaller than that of the BP neural network and better linearity.

A High-Pressure Sensor With High Linearity With S-Shaped Piezoresistors

Silicon piezoresistive pressure sensors are widely used, and the pursuit of high linearity and high accuracy of sensors is always there. In this article, through simulations and calculations, including higher order piezoresistance effects, an S-shaped piezoresistor is proposed to optimize the linearity of pressure sensors; that is, the piezoresistive connecting arms are also lightly doped silicon. Two kinds of silicon piezoresistive absolute pressure sensors with a circular diaphragm in the range of 0–60 MPa were designed and fabricated, respectively, with tri-meander-shaped piezoresistors and S-shaped piezoresistors. After measurement, the linearity of the pressure sensor with S-shaped piezoresistors is about 30% better than that of the sensor with tri-meander-shaped piezoresistors, and the linearity and accuracy can reach 0.045% FS and 0.054% FS under the voltage source.

Low-Cost Sensor for Continuous Measurement of Brix in Liquids

This paper presents a Brix sensor based on the differential pressure measurement principle. Two piezoresistive silicon pressure sensors were applied to measure the specific gravity of the liquid, which was used to calculate the Brix level. The pressure sensors were mounted inside custom-built water-tight housings connected together by fixed length metallic tubes containing the power and signal cables. Two designs of the sensor were prepared; one for the basic laboratory testing and validation of the proposed system and the other for a fermentation experiment. For lab tests, a sugar solution with different Brix levels was used and readings from the proposed sensor were compared with a commercially available hydrometer called Tilt. During the fermentation experiments, fermentation was carried out in a 1000 L tank over 7 days and data was recorded and analysed. In the lab experiments, a good linear relationship between the sugar content and the corresponding Brix levels was observed. In the fermentation experiment, the sensor performed as expected but some problems such as residue build up were encountered. Overall, the proposed sensing solution carries a great potential for continuous monitoring of the Brix level in liquids. Due to the usage of low-cost pressure sensors and the interface electronics, the cost of the system is considered suitable for large scale deployment at wineries or juice processing industries.

A package for piezoresistive pressure sensors with embedded built-in self-test function based on bimetallic actuator

Piezoresistive pressure sensors have been widely used in the industry and many other fields. However, conventional pressure sensor inspection is performed with the device off, which causes several inconveniences. In this article, an electrothermal actuator is designed and fabricated on the basis of bimetallic alloy material to realise the self-test of the piezoresistive silicon pressure sensor, and a kind of pressure sensor package structure with self-test capability is developed using the electrothermal actuator. Experimental results show that the structure can realise the dual excitation of the pressure and temperature of the diffused silicon pressure sensor core and enable it to return to the normal working state in less than 3.3 s. The self-test module can be driven at a low voltage of 0.8 V at less than 618 mW and can reflect the performance of the pressure sensor quickly and accurately. The structure is suitable for most differential pressure, absolute pressure sensor chips.

730 Clinical utility of the portable pressure measuring device for garment therapy on burn scar

IntroductionThe experimenters developed a portable pressure measuring device using silicon piezoresistive pressure sensors. The purpose of this study was to determine the effectiveness of pressure garment therapy using proposed device with objective data obtained through a randomized controlled trial.MethodsPressure measurements were acquired through a readout circuit consisting of an analog-to-digital converter, a microprocessor, and a Bluetooth transmission module for wireless data transmission to an external device. This was a double-blinded, randomized, controlled trial in patients with hypertrophic scars. In the pressure monitoring group, garment pressures were monitored using the portable pressure measuring device, and the compression garment was adjusted so that the pressure was maintained at the therapeutic range of 15 – 25 mmHg. In the control group, non-surgical standard treatment of burn scars except for pressure monitoring was performed in the same manner.ResultsNo significant intergroup difference was noted at the initial evaluations (p >0.05) between two groups. The pre- to post-treatment change in the scar thickness (p=0.03) and erythema (p=0.03), more reductions were found in the pressure monitoring group than control group. There were no significant differences in the change measurements between the two groups for melanin levels (p=0.62) and transepidermal water loss (TEWL) (p=0.94). The changes (skin distensibility, biological skin elasticity, gross skin elasticity, and skin viscoelasticity) measured with the cutometer showed no significant differences between the two groups (p=0.87, p=0.32, p=0.37, and p=0.29, respectively).ConclusionsComplementary characteristics such as wireless transmission to an external device may allow burn patients to continuously wear the device for real-time measurements. A Portable pressure monitoring device is effective for significantly improving burn-associated scar characteristics.

Comparison between the portable pressure measuring device and PicoPress® for garment pressure measurement on hypertrophic burn scar during compression therapy

PurposeThe current standard treatment for hypertrophic scars following burn injury is pressure garment therapy. The experimenters developed the novel portable pressure measuring device using silicon piezoresistive sensors. As PicoPress® is the most accurate (i.e., lowest variation and error) manometric sensor for pressure measurement, we sought to compare and examine the accuracy of the novel device regarding in vitro pressure measurements at the hypertrophic scar–pressure garment interface. MethodsThe novel device was designed to operate in non-corrosive media, such as air. The device can use up to six pressure sensing points and was developed to adjust the number of pressure sensors according to the size of the scar. Pressure measurements were acquired through a readout circuit consisting of an analog-to-digital converter, a microprocessor, and a Bluetooth transmission module for wireless data transmission to an external device. All signals were converted into mean pressure expressed in millimeters of mercury (mmHg). The mean pressure values measured by the sensors were compared to those obtained from PicoPress®. 55 garment pressures recordings were obtained from the sensors over this study conducted in 2018–February 2020. We then analyzed the test–retest reliability using the intraclass correlation coefficients (ICC). PicoPress® was also employed in the same pressure garments for obtaining similar measurements. A two way random effects model ICC with 95% confidence intervals was used to compare the mean pressure values obtained from the silicon piezoresistive sensors to the PicoPress® measurements. ResultsThe test–retest reliability of the pressure sensors was close to the acceptable level for clinical use regarding stationary interface pressure measurement (ICC = 0.99, 95% CI 0.990−0.997). The mean pressure obtained from the silicon piezoresistive pressure sensors showed an accordance with the measurements from PicoPress® (ICC = 0.97, 95% CI 0.947−0.985). ConclusionThe novel device may present a viable alternative to PicoPress® for garment pressure measurements. In addition, the novel device improves adaptability to the hypertrophic scar shape and size. Complementary characteristics such as wireless transmission to an external device may allow burn patients to continuously wear the device for real-time measurements during pressure garment therapy, thus improving existing devices including PicoPress®.

A Novel Packaging Structure and Process for High Temperature Silicon Piezoresistive Pressure Sensor

A Novel Packaging Structure and Process for High Temperature Silicon Piezoresistive Pressure Sensor

A theoretical calculation for carrier concentration and resistance prediction

Due to lack of analytical solutions for equation of electrical neutrality under thermal equilibrium conditions, a novel and efficient numerical iteration technique was developed. The computational carrier concentration obtained by this new numerical method is in good correlation to commonly cited values and experimental data. Based on this new numerical method effects of some factors on the resistance of silicon piezoresistive pressure sensor were analyzed. Results show that no matter doping concentration is high or low the minority carrier exclusion effect disappears under considerably high current conditions, and increases in bias current induce greater maximum operating temperature; increases in doping concentration can increase the maximum operating temperature and decrease temperature coefficient of resistance.

Relative Contributions of Packaging Elements to the Thermal Hysteresis of a MEMS Pressure Sensor

Piezoresistive silicon pressure sensor samples were thermally cycled after being consecutively packaged to three different levels. These started with the absolute minimum to allow measurement of the output and with each subsequent level incorporating additional packaging elements within the build. Fitting the data to a mathematical function was necessary both to correct for any testing uncertainties within the pressure and temperature controllers, and to enable the identification and quantification of any hysteresis. Without being subjected to any previous thermal preconditioning, the sensors were characterized over three different temperature ranges and for multiple cycles, in order to determine the relative contributions of each packaging level toward thermal hysteresis. After reaching a stabilised hysteretic behaviour, 88.5% of the thermal hysteresis was determined to be related to the bond pads and wire bonds, which is likely to be due to the large thermal mismatch between the silicon and bond pad metallisation. The fluid-fill and isolation membrane contributed just 7.2% of the total hysteresis and the remaining 4.3% was related to the adhesive used for attachment of the sensing element to the housing. This novel sequential packaging evaluation methodology is independent of sensor design and is useful in identifying those packaging elements contributing the most to hysteresis.

Design of Treatment System for Poor Peripheral Circulation Using Air Wave Pressure Based on STM32 Microprocessor

This study designs an intermittent pneumatic pressurization device with STM32 series single chip as the core. The working state of the air pump and the plurality of air chambers is controlled by the IO port of the single chip microcomputer, and the circulating inflation of the plurality of air bags is realized. The pressure monitoring system consists of a silicon piezoresistive pressure sensor, a high-precision operational amplifier and a 12-bit AD converter which monitors the gas pressure of each gas path in real time to ensure the safety of the equipment. The system is easy to operate, simple in function, and has strong practicability.

Temperature Compensation of Piezo-Resistive Pressure Sensor Utilizing Ensemble AMPSO-SVR Based on Improved Adaboost.RT

As the silicon material is severely influenced by the ambient temperature, the silicon piezo-resistive pressure sensor remarkably suffers from a strong nonlinearity in the response characteristic as the ambient temperature varies. To address this crucial issue, an adaptive mutation particle swarm optimization optimized support vector regression (AMPSO-SVR) combined with improved AdaBoost.RT algorithm is presented. The opposition-based learning initialization and Levy mutation is applied in the adaptive mutation particle swarm optimization (AMPSO) to achieve the appropriate model selection task which directly determines the performance of SVR. The performance of original AdaBoost.RT is improved by a dynamical modification approach for threshold and quoted error criterion. In order to verify the effectiveness of the proposed temperature compensation approach, several additional optimization methods such as Cuckoo search (CS), dragonfly algorithm (DA), multi-verse optimizer (MVO), conventional particle swarm optimization (PSO), Levy flight improved particle swarm optimization (Levy-PSO) and the AMPSO combined with SVR are investigated. The minimum quoted error, maximum quoted error, the mean quoted error and the variance of the quoted error over testing data obtained by the proposed method are $6.8764\times 10^{-5}$ , $6.4463\times 10^{-4}$ , $3.2619\times 10^{-{4}}$ and $2.5714\times 10^{-8}$ respectively, which are superior to the corresponding indices obtained by other methods. The analysis of simulation results indicates the method proposed in this research is applicable, effective and efficient for industrial application.

A High Precision Software Compensation Algorithm for Silicon Piezoresistive Pressure Sensor

There are generally zero drift, sensitivity drift and nonlinear error in silicon piezoresistive pressure sensors due to the inherent characteristics of semiconductor materials. It is necessary to compensate and correct the errors produced so as to meet the requirements of measurement accuracy. In order to further improve the compensation precision, based on the research of various basic software compensation methods, a surface fitting compensation algorithm based on least square method is designed, and the software is implemented on the Visual Basic platform. The experimental results show that the zero drift, sensitivity drift and nonlinear error is effectively eliminated, and the output precision of the sensor is greatly improved.

A chip-level oven-controlled system used to improve accuracy of silicon piezoresistive pressure sensor

High precision is an important indicator for the silicon piezoresistive pressure sensor, which is deeply affected by the ambient temperature. This paper presented a chip-level oven-controlled system to operate the silicon piezoresistive pressure sensor at a constant temperature. However, the changes in ambient temperature still affect the temperature of the silicon piezoresistive pressure sensor due to the non-coplanar temperature control and the direct heat transfer between the piezoresistance on the surface of the pressure sensor and the environment. In order to decrease the effects and further improve the accuracy of the silicon piezoresistive sensor, a compensation function was introduced in the designed system. In addition, the oven-controlled structure fabricated by the MEMS process and the silicon piezoresistive pressure sensor were implemented at the chip level, which further reduced power consumption. The feasibility of the design was verified by the results of the thermodynamic model and COMSOL Multiphysics simulation analysis. Test results showed that when the pressure ranged from 100 hPa to 1100 hPa, the designed system performed a maximum measurement error no more than ±0.2 hPa from −45 °C to 45 °C. After compensation, the accuracy, sensitivity temperature coefficient, offset temperature coefficient of the silicon piezoresistive pressure sensor can reach 0.02% FS, 1.081 × 10−5/°C, 2.22 × 10−4% FS/°C respectively.

The analytical calibration model of temperature effects on a silicon piezoresistive pressure sensor

Presently, piezoresistive pressure sensors are highly demanded for using in various microelectronic devices. The electrical behavior of these pressure sensor is mainly dependent on the temperature gradient. In this paper, various factors,which includes effect of temperature, doping concentration on the pressure sensitive resistance, package stress, and temperature on the Young’s modulus etc., are responsible for the temperature drift of the pressure sensor are analyzed. Based on the above analysis, an analytical calibration model of the output voltage of the sensor is proposed and the experimental data is validated through a suitable model.

Temperature measurement performance of silicon piezoresistive MEMS pressure sensors for industrial applications

Temperature and pressure are the most common parameters to be measured and monitored not only in industrial processes but in many other fields from vehicles and healthcare to household appliances. Silicon microelectromechanical (MEMS) piezoresistive pressure sensors are the first and the most successful MEMS sensors, offering high sensitivity, solid-state reliability and small dimensions at a low cost achieved by mass production. The inherent temperature dependence of the output signal of such sensors adversely affects their pressure measurement performance, necessitating the use of correction methods in a majority of cases. However, the same effect can be utilized for temperature measurement, thus enabling new sensor applications. In this paper we perform characterization of MEMS piezoresistive pressure sensors for temperature measurement, propose a sensor correction method, and demonstrate that the measurement error as low as ? 0.3?C can be achieved.

A novel temperature compensated piezoresistive pressure sensor

The main drawback of current piezoresistive pressure sensors is the drop of output voltage with increase in the operating temperature which severely reduces the measurement accuracy. This paper presents a novel passive technique for temperature compensation of silicon piezoresistive pressure sensors. The built-in compensation technique eliminates the need for expensive and time consuming calibration process required for each sensor inside a fabricated batch. In this technique, extra polysilicon resistors with negative Temperature Coefficient of Resistivity (TCR) are employed for compensation purpose. Through applying this technique, Temperature Coefficient of Sensitivity (TCS) of the conventional non-compensated sensor was reduced to zero. Analytically derived equations and verified Finite Element Model considering mechanical, piezoresistive and electrical characteristics of the sensor are adapted to analyze the behavior of the sensor. The implementation of the introduced technique is compatible with conventional MEMS devices fabrication process. The compensated sensor is advantageous for pressure measurement in harsh environments with temperature variations.

Erratum to: Design principles and considerations for the ‘ideal’ silicon piezoresistive pressure sensor: a focused review

Erratum to: Design principles and considerations for the ‘ideal’ silicon piezoresistive pressure sensor: a focused review