US 6,308,572 B1 · Gas concentration sensor

Abstract

A gas concentration sensor comprises an ultrasonic element 33 opposite a reflection surface 34. A depression 34a is formed on an edge portion of a reflection surface 34 which is in contact with a side wall of a measurement chamber 32 such that a bottom surface of the depression 34a is substantially in parallel with the reflection surface 34. The distance between the ultrasonic element 33 and the edge portion of the reflection surface 34 becomes greater than the distance between the ultrasonic element 33 and a central portion of the reflection surface 34. As a result, an indirect wave, which impinges obliquely on the side wall of the measurement chamber 32 and propagates along the side wall, is reflected from the bottom surface of the depression 34a and propagates. Thus, the propagation distance of this indirect wave becomes greater as compared to the case where the reflection surface 34 is flat, so that the indirect wave is not combined with a direct wave in the vicinity of a modulation point of the direct wave. That is, since the modulation point of the direct wave can be detected accurately, a time interval between a modulation point of a transmitted wave and that of a received wave can be measured as the propagation time of an ultrasonic wave, thereby enabling accurate determination of gas concentration.

Claims45

Dependent claims

A gas concentration sensor comprising:

a measurement chamber having an inflow path for allowing inflow of gas under measurement thereinto and an outflow path for allowing outflow of the gas therefrom;
an ultrasonic element disposed on one of two wall surfaces located in opposition to each other within said measurement chamber, and capable of transmitting an ultrasonic wave toward the other of the two wall surfaces and receiving an ultrasonic wave reflected from the wall surface serving as a reflection surface;
and
gas concentration detection means for causing said ultrasonic element to transmit an ultrasonic wave and to receive the reflected wave, for measuring a propagation time between transmission of the ultrasonic wave and reception of the reflected wave, and for determining a concentration of a specific gas contained in the gas under measurement on the basis of the propagation time,
said sensor being characterized in that said measurement chamber is formed such that a distance between an edge portion of the reflection surface and said ultrasonic element is greater than a distance between a central portion of the reflection surface and said ultrasonic element.

2 more elements

A gas concentration sensor comprising:

a measurement chamber having an inflow path for allowing inflow of gas under measurement thereinto and an outflow path for allowing outflow of the gas therefrom;
an ultrasonic element disposed on one of two wall surfaces located in opposition to each other within said measurement chamber, and capable of transmitting an ultrasonic wave toward the other of the two wall surfaces and receiving an ultrasonic wave reflected from the wall surface serving as a reflection surface;
and
gas concentration detection means for causing said ultrasonic element to transmit an ultrasonic wave and to receive the reflected wave, for measuring a propagation time between transmission of the ultrasonic wave and reception of the reflected wave, and for determining a concentration of a specific gas contained in the gas under measurement on the basis of the propagation time,
said sensor being characterized in that an area of the reflection surface of said measurement chamber is not less than an area of an opening surface of said ultrasonic element.

2 more elements

A gas concentration sensor comprising:

a measurement chamber having an inflow path for allowing inflow of gas under measurement thereinto and an outflow path for allowing outflow of the gas therefrom;
an ultrasonic element disposed on one of two wall surfaces located in opposition to each other within said measurement chamber, and capable of transmitting an ultrasonic wave toward the other of the two wall surfaces and receiving an ultrasonic wave reflected from the wall surface serving as a reflection surface;
and
gas concentration detection means for causing said ultrasonic element to transmit an ultrasonic wave and to receive the reflected wave, for measuring a propagation time between transmission of the ultrasonic wave and reception of the reflected wave through detection of a specific position in a waveform of the ultrasonic wave, and for determining a concentration of a specific gas contained in the gas under measurement on the basis of the propagation time,
said sensor being characterized in that said measurement chamber is formed such that a distance between a central portion of the reflection surface and said ultrasonic element is at least 60 mm.

2 more elements

A gas concentration sensor comprising:

a measurement chamber having an inflow path for allowing inflow of gas under measurement thereinto and an outflow path for allowing outflow of the gas therefrom;
an ultrasonic element disposed on one of two wall surfaces located in opposition to each other within said measurement chamber, and capable of transmitting an ultrasonic wave toward the other of the two wall surfaces and receiving an ultrasonic wave reflected from the wall surface serving as a reflection surface;
and
gas concentration detection means for causing said ultrasonic element to transmit an ultrasonic wave and to receive the reflected wave, for measuring a propagation time between transmission of the ultrasonic wave and reception of the reflected wave, and for determining a concentration of a specific gas contained in the gas under measurement on the basis of the propagation time,
said sensor being characterized in that a cross-sectional area of the outflow path is smaller than a cross-sectional area of the inflow path.

2 more elements

Dependencies are inferred from the claim text.

Gas concentration sensor

Life of this patent

Gas concentration sensor

Life of this patent

Abstract

Claims45