Disclosed is a signal processing apparatus comprising a sensor whose impedance varies according to changes in quantity sensed thereby, a power source applying a voltage to the sensor, a current/voltage conversion circuit for converting an output of current flowing through the sensor to a voltage signal,...http://www.google.com.tw/patents/US4870262?utm_source=gb-gplus-share專利 US4870262 - Signal processing apparatus and binary encoder circuit for the same
