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Recently there is demand for rotation sensors capable of high-accuracy detection and very low-speed detection of rotation at high temperature for automobile use. To meet this requirement, a rotation sensor using an InSb thin-film magneto-resistors with good thermal stability has been developed. This sensor transduces magnetic flux change due to gear rotation to resistance change. It is composed of InSb thin-film magneto-resistors fabricated by a newly developed process and signal shaping circuits where resistor signals are converted to digital signals using no amplifier. Accordingly, the signals are independent of the measured frequencies, making possible very low speed (0 to 20 Hz) detection. The sensor stably operates in the temperature range from -40 to 150 degree C for thousands hours. There is no need for a shielded harness due to the digital output signal.

The purpose of this paper is to outline some of the approaches to provide an exhaust gas high temperature sensor with wide temperature detection range and fast responsiveness. Conventional exhaust gas temperature sensors were designed only to detect an overheating catalyst, so they were unable of detecting temperatures below 600°C. Their slow responsiveness prevented them from detecting rapid catalyst temperature changes. The development of a new thermistor material enabled the sensor to measure a wide temperature range of 300°C to 1000°C. This new sensor provides fast response time (x = 8.7seconds.) as well as durability capability to 1000°C Applications for this sensor include in catalyst preheating and OBD-II systems.

High temperature exhaust gas sensors have been used since 1975 to monitor catalyst overtemperature in the Japan auto market. Heated catalyst systems introduced to meet LEV and ULEV will make use of high temperature sensors for control and diagnosis. This paper describes the history and the evolution of these sensors. The three leading sensor technologies consisting of thermistors, thermocouples, and resistive temperature detectors (RTD) are described. Interface and system requirements for each of the sensor technologies are summarized. Sensor response time characteristics interaction with system design are covered.