Ngk Insulators, Inc.

Yuichi Sasaki

Jun Usami

Osamu Nakasone

Hiroshi Kurachi

Takeya Miyashita

Akinobu Hattori

A method of correcting an output of a NOx sensor including: a first step of obtaining a sensor-variation relational expression based on a relationship between an Ip/Ipvalue and an output change percentage for a calibration sensor; a second step of obtaining, from the relational expression, an output change percentage &#x3b2; that corresponds to an Ip/Ipvalue of a subject NOx sensor; a third step of calculating a pressure correction coefficient &#x3b1; based on the obtained &#x3b2;; and a fourth step of performing output correction on the subject NOx sensor by calculating the pumping current Ip(p) under a reference pressure based on the pumping current Ip(p) and a pressure p of the measurement gas which are detected upon measurement of the NOx concentration in the measurement gas.

Method of correcting output of NOx sensor

A gas sensor includes a first space for a measurement gas from a gas-introducing hole via a first diffusion rate-determining section, a main pumping means for controlling a partial pressure of oxygen in the measurement gas introduced into the first space to have a predetermined value, a second space for the measurement gas from the first space via a second diffusion rate-determining section, and a measuring pumping means for reducing or decomposing a NOx component in the measurement gas introduced from the second space via a third diffusion rate-determining section so that oxygen produced thereby is pumped out to detect a current generated by pumping out the oxygen. A ratio (Wc/We) between a width (We) of an end of a sensor element and a width (Wc) of the gas-introducing hole is not less than 0.3 and less than 0.7.

Gas sensor

A circuit is utilized for measuring a diffusion-limited current which flows through a diffusion-limited current element in proportion to an oxygen concentration which includes an output resistor connected in series with the element, a differential amplifier having a first input connected to a reference voltage supply source, a second input connected to ground, an output connected to the output resistor, and a feedback resistor connected between the first input of the differential amplifier and a point between the element and the output resistor, so that a bias voltage applied across the element is kept constant.

Circuit for measuring diffusion-limited current

An oxygen analyzing method for determining a positive or negative oxygen concentration of a measurement gas which changes between oxidizing and reducing atmospheres. The method uses a sensing element having an oxygen sensing cell wherein an electromotive force is induced between its measuring and reference electrodes according to the principle of an oxygen concentration cell. The atmosphere adjacent to the measuring electrode is controlled by controlling a pumping current to be applied to an oxygen pumping cell such that the electromotive force induced in the sensing cell is maintained at a predetermined level. A heater is provided to heat the sensing and pumping cells, to maintain their operating temperature within a range of 700.degree.-960.degree. C. The pumping current, or a signal to control the pumping current, is converted into an oxygen concentration signal whose level is held within one of a positive range and a negative range. The concentration signal represents the positive oxygen concentration of the oxidizing atmosphere, or the negative oxygen concentration of the reducing atmosphere.

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Nagoya, Japan

Yuichi Sasaki