Patent ID: 8257565
Filing Date: 2012-09-04
Classification: G01N

Abstract:
1. A sensor control apparatus for use with a sensor element as a controlled object having a solid electrolytic layer and capable of producing an element current responsive to a concentration of a particular component of a measured gas when a voltage is applied to the sensor element, the sensor element having resistance and capacitance included therein, the sensor control apparatus comprising: an applied voltage control circuit for variably controlling the voltage applied to the sensor element; and a current measurement resistance having one terminal connected to the sensor element and having another terminal connected to a reference voltage in a current path over which the element current flows when the voltage is applied to the sensor element under the control of the applied voltage control circuit, wherein an intermediate voltage representing an amount of the element current is measured at an intermediate point where the voltage applied to the sensor element is divided by the resistance of the sensor element and the current measurement resistance, wherein the applied voltage control circuit includes an inverting or a noninverting amplifier circuit to which the intermediate voltage appearing at the intermediate point between the sensor element and the current measurement resistance is inputted, and a capacitor connected in parallel to a feedback resistance of an operational amplifier of the amplifier circuit, and the applied voltage control circuit being feed-back controlled based on the intermediate voltage in a feed-back loop where the sensor element, the current measurement resistance, a filter circuit and the amplifier circuit are connected with each other, and wherein the applied voltage control circuit determines the applied voltage to the sensor element based on the intermediate voltage.