Masanori Tanabe

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.

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.

Method of producing semiconductor displacement transducer

A strain gauge is formed on one main surface of a semiconductor single crystal substrate while an insulating oxide film is formed on the other main surface of the substrate. A metal junction layer including several layers inclusive of eutectic alloy layers is formed on the surface of the insulating oxide film and the thus prepared structure is mounted on a metal strain generator. By heating this assembly to temperatures approximating to the eutectic point of the eutectic alloy layer, the semiconductor substrate and the metal strain generator are joined together.

Overwrite performance for high‐coercivity particulate media

A model of overwrite based on anisotropy field distributions of particles has been proposed for γFe2O3 and Co‐γFe2O3 high‐coercivity particulate media. In this model, overwrite is determined by the ratio of the number of nonreversed particles to the total number of particles. The magnitude and angle distributions of the anisotropy field were obtained by torque magnetometer measurements. From these observed distributions, switching field distributions of the particles were derived using the curling model for an infinite cylinder. The write field of thin‐film heads was calculated using a finite element method. The nonreversal ratio in the medium was given by both the switching and the write fields. The calculated overwrite values were obtained from this ratio and were found to be in good agreement with the measured ones. This model was valid for the media which differed in the distributions of the anisotropy field. The overwrite performance can be improved by narrowing the anisotropy field distributions of ...

Effect of Side-Fringing Field on Read-Write Characteristics for Thin Film Magnetic Heads

The side-fringing fields of thin film heads were studied using three-dimensional simulations. Playback signals were calculated using the reciprocity principle. The output as a function of linear density was calculated by superpositioning of isolated pulses. The results of three-dimensional calculations of isolated pulses, off-tracking and output as a function of linear density, agreed with measurements. These calculations and measurements indicated that the effect of the side-fringing field appears in the isolated pulses from narrow-track heads. It was found that asymmetry in isolated pulses results from the effect of the side-fringing field. By narrowing the track width, the effect of the side-fringing field is increased. Playback pulses from the outside of the track are broader than those at the track center, and so the resolution of narrow-track heads decreases.