The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 16, 2002
Filed:
Jan. 11, 2000
Yoshikuni Sato, Aichi, JP;
Noboru Ishida, Gifu, JP;
Hideki Ishikawa, Aichi, JP;
Takafumi Oshima, Aichi, JP;
Yasushi Sato, Aichi, JP;
NGK Spark Plug Co., Ltd, Aichi, JP;
Abstract
When a sensor has deteriorated, the propagation time T ′ of a first reflection wave becomes greater than the propagation time T of a first reflection wave as measured in a new sensor. If measurement of the concentration of a specific gas is based on the propagation time T of the first reflection wave as measured in the new sensor, gas concentration cannot be determined accurately. By contrast, a reflection wave other than the first reflection wave (for example, a second reflection wave) is merely reflected off the surface of the ultrasonic element and is not affected by the internal structure of the ultrasonic element. Therefore, even when the sensor is deteriorated, the propagation time T T ′ of the second reflection wave exhibits less variation and is less susceptible to deterioration of the sensor. Therefore, the concentration of a specific gas is determined on the basis of the propagation time of the second reflection wave, which is less susceptible to deterioration of the sensor, instead of the propagation time of the first reflection wave, which is more susceptible to deterioration of the sensor. Thus, gas concentration can be measured accurately.