Measuring and testing – Gas analysis – Gas of combustion
Patent
1998-06-12
2000-07-04
Williams, Hezron
Measuring and testing
Gas analysis
Gas of combustion
422 94, 204424, 73 3105, G01N 700, G01N 2726, G01N 3112
Patent
active
060821760
ABSTRACT:
An NOx-concentration detecting apparatus is disclosed which enables a user to readily know a record of operating conditions of an NOx sensor. The apparatus includes an NOx sensor, pumping-current control means, constant-voltage application means, NOx-concentration detecting means, a heater and writing means for writing to a recorder variation of at least one parameter selected from a first pumping current value, a second pumping current value, the concentration of oxygen contained in the measurement gas and the concentration of NOx in the measurement gas. Also disclosed is an NOx-concentration detecting apparatus capable of determining the concentration of NOx at a high resolution even when different NOx sensors are used. The NOx-concentration detecting apparatus detects the first pumping current I.sub.P1, and the second pumping current I.sub.p2, corrects the detected values based on correction data stored on a floppy disk, and determines the concentration of NOx in the measurement gas using standard characteristics stored in ROM of the ECU, namely, characteristics representing correlations among the first pumping current I.sub.P1, the second pumping current I.sub.p2 and the concentration of NOx in the measurement gas. The correction data are used for making previously measured characteristics of the NOx sensor equal to the standard characteristics, which characteristics represent correlations among the first pumping current I.sub.P1, the second pumping current I.sub.p2 and the concentration of NOx in the measurement gas. Accordingly, when the concentration of NOx in the same measurement gas is measured using different NOx sensors, any of the NOx sensors can provide an accurate measurement.
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Inagaki Hiroshi
Kondo Noriaki
NGK Spark Plug Co. Ltd.
Williams Hezron
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