Yoshitaka Matsuoka

A special silicon diaphragm pressure sensor with high output and high accuracy

Abstract A conventional silicon diaphragm sensor cannot be used in a low pressure range that requires high output and high accuracy. This disadvantage arises from a large pressure-induced deflection of the diaphragm, which is known as the balloon effect. In order to solve this problem, a silicon diaphragm with a center boss has been developed. In this sensor, an annular groove is formed in the back surface of the diaphragm and diffused piezoresistive gagues are formed radially adjacent to the outer and inner edges of the groove on the top surface. Experimental results are explained by a two-cantilever model. The accuracy of this sensor (0.17% of full scale) is ten times better than that of a conventional one in the low pressure range (5 to 100 kPa full scale) and is the same under front and back pressures. These characteristics are achieved in a wide temperature range, from −40 to 120 °C.

Design Considerations for Silicon Circular Diaphragm Pressure Sensors

The design of silicon circular-diaphragm pressure sensors was considered in order to develop highly-accurate pressure sensors. A relatively simple method of stress analysis was proposed. The anisotropy of the elastic properties of silicon, the large deflections of the plates, and elastic deformations of the support structures were taken into account in the stress analysis by the plate theory and the finite element method. Output voltages and their nonlinearities were calculated by applying stress analysis and piezoresistive sensor theories. The calculated results are in close agreement with the experimental results.

Differential Pressure/Pressure Transmitters Applied with Semiconductor Sensors

The optimum design for silicon diaphragm-type pressure sensors and that for a sensing body of the transmitters have been considered. Three types of sensors, which have different section shapes, have been developed for measuring wide-range pressure with high sensitivity and good linearity. The transmitters of the range from 0-100 Pa up to 0-50 MPa with an accuracy of 0.2 percent have been developed. For a differential pressure transmitter a three-metal diaphragm structure has been devised to protect the sensor from an overpressure. The characteristics of the transmitters are high accuracy, high reliability, and long-term stability.

Characteristic analysis of a pressure sensor using the silicon piezoresistance effect for high-pressure measurements

The characteristics of output voltages and non-linearities of a silicon circular diaphragm pressure sensor using the piezoresistance effect are analysed for high-pressure measurements. The pressure sensor is analysed, using triaxial stresses and their corresponding piezoresistance coefficients, by a finite-element method (FEM). Radial and tangential stresses on the circular diaphragm, calculated by the FEM at a pressure of 50 MPa, shift by about 125 MPa to the compressive side from those calculated by plate theory of a fixed periphery. Moreover, the perpendicular stress (z stress) component to the diaphragm surface is not negligible at high pressure in either calculation. The results calculated by the FEM agree well with the experimental results. A pressure sensor for high-pressure measurements from 0 to 50 MPa is then designed and fabricated. It has a non-linearity within +or-0.1%.

Low-pressure measurement limits for silicon piezoresistive circular diaphragm sensors

The lower limit to a practical measurable span is investigated for pressure sensors that have a silicon diaphragm with circular shape and employ piezoresistive gages. Output voltages and non-linearities of the sensors are analysed, taking into account the effects of the diaphragms large deflection and the piezoresistive effect non-linearities. Based on this analysis and industrial requirements (the minimum span output voltage must be larger than 4.3 mV V-1 and non-linearities must be within +or-0.2% at the same time), it is found that the minimum span is 15 kPa.

Field-induced strain of shape memory alloy Fe-31.2%pd using a capacitance method in a pulsed magnetic field

A system for the simultaneous measurement of magnetization and magnetic strain, which is designed to be used in a pulsed magnetic field, has been developed. In this system, a capacitor on a sample is used and its capacitance changes with the displacement of a sample due to the strain on the sample in a magnetic field. The most significant feature of this system is that magnetization and strain can be measured simultaneously. It is useful to compare the magnetization and magnetic strain (magnetostriction) with each other. Using this system, we have studied the precise magnetization and magnetic field-induced strain (MFIS) of the martensite metallic compound Fe–31.2%Pd (at.%) at temperatures down to 80 K in martensite phase, which is much lower than the martensitic transformation temperature TM=230 K. Large MFIS has been measured under a pulsed magnetic field with the time constant 6 ms, which corresponds to 80 Hz in frequency. It means that the MFIS occurs even in short-pulse magnetic fields.

Design method for sensing body of differential pressure transmitter using silicon diaphragm-type pressure sensor

This paper describes a design method for the three-diaphragm-type sensing body of a differential pressure transmitter. This sensing body protects the silicon diaphragm-type pressure sensor from over-pressure. The design method includes information on how to decide the stiffness of each metal diaphragm and the liquid quantity needed to fill the sensing body. The differential pressure transmitter, with significant stabilities, has zero-influence errors of static pressure and over-pressure of less than -0.2% and /spl plusmn/0.1%, respectively, and is obtained at a measuring span of 25 kPa and a line pressure of 15 MPa. >

Designing method for sensing body mechanism of differential pressure transmitter using silicon diaphragm type pressure sensor

This paper describes a designing method of the three-diaphragm type sensing body of differential pressure transmitter for protecting silicon diaphragm type pressure sensor from an over-pressure. This method includes how to decide each stiffness of three metal diaphragms and liquid quantity filled in the sensing body. This method is applied to differential pressure transmitters with measuring ranges from 0-0.6 kPa to 0-400 kPa. As a result, transmitters with significant stabilities are obtained: a zero and span influence of a static pressure and an over-pressure are less than 0.2% at a line pressure of 15 MPa.<<ETX>>

THICK FILM TEMPERATURE COMPENSATING CIRCUIT FOR SEMICONDUCTOR STRAIN GAUGES

Thick film circuits were developed for temperature compensating of semiconductor strain gauges and for connecting the gauges to amplifiers in electronic pressure and differential pressure transmitters. In each circuit, ten Au pads for Al wire bonding and thirteen Ag/Pd pads for soldering must be fabricated on a small substrate. The results of the research are shown below.

A Thick Film Hybrid IC Amplifier for Industrial Use

Electronic circuits for industrial uses must satisfy the following requirements: low sensitivity to changes in the surrounding temperature, high reliability, and small size. In the amplifier for a pressure transmitter described here, the temperature dependences of its properties, Zero point and Span, are intensively influenced by TCRs of the resistors used, and by a mismatching of the temperature dependences of the off-set voltages between the two operational amplifier IC chips. As forthe thick film resistors, it has been cleared that the DuPont 1700 series resistor pastes are the most suitable:TCRs of less than