Nagano Keiki Co., Ltd.

Kazuya Yamagishi

Munenori Tsuchiya

Shigemitsu Ogawa

A processor of a signal processing circuit for calibrating an electro-capacitance pressure sensor includes a coefficient arithmetic section for calculating calibration value and a calibration arithmetic section. The calibration arithmetic section calculates an electro-capacitance ratio between electro-capacitance C and C detected by an electro-capacitance pressure sensor and conducts a calibration calculation from the electro-capacitance ratio to output a converted pressure value. The processor includes a fundamental arithmetic section for conducting a calculation given by f&equals;(Z&minus;W)/(X&minus;Y) for predetermined arguments X, Y, Z and W input by the coefficient arithmetic section or the calibration arithmetic section and for outputting the calculation result f to the one of the coefficient arithmetic section and the calibration arithmetic section providing the input. The fundamental arithmetic section provides shared calculating for the coefficient calculation and calibration calculation.

Signal processing circuit of sensor

A self-calibrating sensor includes a sensor element for electrically detecting change in physical amount of a workpiece. A signal output device detects changes of the sensor element to output an electric signal. A processor conducts calibration calculation for the electric signal to adjust to the physical amount of the workpiece. A memory stores calculation results of the processor. The processor includes a calibration value calculating circuit for calculating a calibration value by conducting the calibration calculation based on a predetermined transforming formula and a calibration completion determining circuit for determining whether calculation of the calibration value by the calibration value calculating circuit is completed or not. The presence of the calibration value calculating circuit and the calibration completion determining circuit eliminates the need for connecting to an outside computer through an exclusive line for calculating the calibration value. Accordingly, an exclusive I/O line for calibration work is omitted as compared to conventional self-calibrating sensors.

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Tokyo, Japan

Kazuya Yamagishi