Measuring and testing – Gas analysis – Gas chromatography
Patent
1978-09-05
1979-12-18
Kreitman, Stephen A.
Measuring and testing
Gas analysis
Gas chromatography
123 32EE, 123119EC, G01N 2746
Patent
active
041787935
ABSTRACT:
A vehicle engine exhaust mounted oxygen sensor of the type producing an internally generated signal voltage and having a variable internal impedance is connected in series with a reference impedance and a semiconductor switch, the semiconductor switch having an impedance which may become large when current therethrough is very low. A constant current source is connected to supply current to the junction of the sensor and reference impedance at one sensor terminal and thus guarantee a minimum current and small switch impedance when the sensor impedance is large. Further apparatus samples the magnitudes of the voltage at the one sensor terminal with the semiconductor switch in its conducting and non-conducting states, the ratio of said magnitudes varying with sensor impedance. The ratio can be compared with one or more references to provide a warm sensor signal or control the operation of a sensor heater.
REFERENCES:
patent: 3616274 (1971-10-01), Eddy
patent: 3938479 (1976-02-01), Oberstadt
patent: 4094186 (1978-06-01), Wessel
patent: 4106450 (1978-08-01), Norimatsu et al.
patent: 4120269 (1978-10-01), Fujishiro
patent: 4135381 (1979-01-01), Sherwin
"Lambda-Sensor with Y.sub.2 O.sub.3 Stabilized ZrO.sub.2 Ceramic for Application in Automotive Emission Control Systems", SAE Paper 770401, pp. 53-58.
Bremer Richard J.
Richardson Daniel J.
General Motors Corporation
Kreitman Stephen A.
Sigler Robert M.
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