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An SOI type pressure sensor has been developed which can measure pressure at high temperature environments above 150°C. SOI stands for Silicon On Insulator. A single-crystalline silicon layer is located on an insulating layer formed on a silicon substrate. The piezoresistors of the SOI type pressure sensor are made from the single-crystalline silicon layer which is isolated from the silicon substrate by the insulating layer. There is no leakage current from the piezoresistors. The SOI structure is made by the laser-recrystallization-method. The properties of the SOI type pressure senor are as good as conventional semiconductor pressure sensors.

A small. low-cost piezoresistive acceleration sensor suitable for automotive applications such as advanced breaking control and suspension control systems has been developed. A piezoresistive semiconductor sensor has such advantages as high output linearity, long-term output repeatability and DC response a piezoelectric sensor doesn't feature. One drawback. however, is that piezoresistive characteristics are quite temperature sensitive: Such that temperature dependence of DC offset and span have to be compensated with a certain electrical circuit. With 1 mV/Vs/G, the low sensitivity of the acceleration sensor [Vs:bridge voltage. G:gravitational acceleration], the temperature shift of DC offset represented in terms of the sensitivity, becomes relatively high.

A switching controlled thermal mass air flow sensor with low electric power dissipation has been developed. This thermal mass air flow sensor is operated by the well-known constant temperature method. In addition to the conventional bridge circuit, the new thermal mass air flow sensor provides a filter and a pulse width-modulation inverter (PWM), which turns the power transistor on and off. Therefore, electric power loss is reduced, so that it is possible to greatly reduce the heat sink of the power transistor. In this paper, we discuss the improved design and performance characteristics of the switching control circuit in comparison with a conventional circuit, as shown in Figure 1. We use a platinum wire of 70 μm diameter for the heating element.

A NEW TYPE FUEL FLOW SENSOR which is based upon heat transfer principle has been developed for automotive applications. The fuel flow sensor presented in this paper utilizes temperature sensitive resistors made of extremely thin platinum films, and is located in the main passage of a conduit opposite to a nozzle. An extraordinarily wide dynamic range and a quick response have been obtained in comparison with conventional methods. The hot film type fuel flow sensor could allow a new microprocessor to control the engine functions, as well as a fuel consumption or a fuel rate meter.