Ultrasonic apparatus and method for measuring the concentration and flow rate of gas

• US 20030136193A1
• Filed: 09/20/2002
• Published: 07/24/2003
• Est. Priority Date: 01/22/2001
• Status: Active Grant

• Current Assignee: Teijin Limited
• Original Assignee: Teijin Limited
• Inventors: Fujimoto, Naotoshi
• Granted Patent: US 6,912,907 B2
• Time in Patent Office: Days
• US Class Current: 73/597
• CPC Class Codes: G01F 1/667 Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
• CPC Class Codes: G01F 1/668 Compensating or correcting for variations in velocity of sound
• CPC Class Codes: G01N 2291/0212 Binary gases
• CPC Class Codes: G01N 2291/0215 Mixtures of three or more gases, e.g. air
• CPC Class Codes: G01N 2291/02809 Concentration of a compound, e.g. measured by a surface mass change
• CPC Class Codes: G01N 2291/02836 Flow rate, liquid level
• CPC Class Codes: G01N 2291/044 Internal reflections (echoes), e.g. on walls or defects
• CPC Class Codes: G01N 2291/048 Transmission, i.e. analysed material between transmitter and receiver
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/024 by measuring propagation velocity or propagation time of acoustic waves
• CPC Class Codes: G01N 29/222 Constructional or flow details for analysing fluids optoacoustic fluid cells G01N29/2425
• CPC Class Codes: G01N 29/30 Arrangements for calibrating or comparing, e.g. with standard objects
• CPC Class Codes: G01N 29/326 compensating for temperature variations

Abstract

An apparatus 100 for measuring a gas concentration comprises a conduit 102 through which an objective gas to be measured flows, a ultrasonic transmitting and receiving element 118 fixed in a straight portion 108 of the conduit, a reflecting plate 122 fixed in the straight portion to face to the ultrasonic transmitting and receiving element, a transmit-receive switching element 124 for switching the operational mode of the ultrasonic transmitting and receiving element between a transmitting mode and receiving mode. The apparatus further comprises a calibration gas source 114 for supplying a calibration gas of which components and component ratio are preliminarily known, temperature sensors 116, 120 for measuring the temperature of the calibration gas flowing through the conduit, a propagation time calculating means 126 for calculating the time period for propagation of the ultrasonic through the calibration gas in the conduit, a calibration means for calibrating the reference distance between the ultrasonic transmitting and receiving element and the reflecting plate based on the calculation results of the propagation time calculating means.

Claims

1. A ultrasonic apparatus for measuring a gas concentration, comprising:

a conduit for flowing an objective gas, the concentration of which is to be measured;

a ultrasonic transmission-reception device mounted to the inside of the conduit;

a reflector mounted to the inside of the conduit to face the ultrasonic transmission-reception device;

a transmission-reception switch for switching the operation mode of the ultrasonic transmission-reception device between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

a calibration gas source for supplying a calibration gas, the component and the component ratio of which are known, to the conduit;

a temperature sensor, disposed in the conduit, for measuring the temperature of the calibration gas flowing through the conduit;

propagation time calculation means for calculating the time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the ultrasonic transmission-reception device receives the ultrasonic waves reflected by the reflector; and

calibration means for calibrating a reference length between the ultrasonic transmission-reception device and the reflector on the basis of the calculation results by the propagation time calculation means.

2. A ultrasonic apparatus for measuring a gas concentration according to claim 1 further comprising linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit;

and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

3. A ultrasonic apparatus for measuring a gas concentration according to claim 1, further comprising temperature regulating means for regulating the temperature of the conduit;

linear expansion coefficient calculating means for calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed; and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

4. (Amended) A method of measuring the concentration of an objective gas by a ultrasonic gas concentration measuring apparatus which comprises, a conduit for flowing an objective gas, the concentration of which is to be measured, a ultrasonic transmission-reception device mounted to the inside of the conduit, a reflector mounted to the inside of the conduit to face the ultrasonic transmission-reception device, and a transmission-reception switch for switching the operation mode of the ultrasonic transmission-reception device between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

the method comprising, prior to the start of the process for measuring the concentration of the gas to be measured, the steps of;

supplying a calibration gas, the component and the component ratio of which are known, to the conduit;

measuring the temperature of the calibration gas flowing through the conduit by a temperature sensor disposed in the conduit;

generating ultrasonic waves by the ultrasonic transmission-reception device;

switching the operation mode of the transmission-reception device from the transmission mode for transmitting the ultrasonic waves to the reception mode for receiving the ultrasonic waves;

calculating propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the ultrasonic transmission-reception device receives the ultrasonic waves reflected by the reflector; and

calibrating a reference length between the ultrasonic transmission-reception device and the reflector on the basis of the calculation results.

5. A method according to claim 4 wherein the ultrasonic gas concentration measuring apparatus further comprising:

linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit; and

the method further comprising the steps of;

measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

6. (Amended) A method according to claim 4, further comprising the steps of calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed;

measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the measured temperature.

7. A ultrasonic apparatus for measuring a gas concentration, comprising:

a conduit for flowing an objective gas, the concentration of which is to be measured;

a first ultrasonic transmission-reception device mounted to the inside of the conduit;

a second ultrasonic transmission-reception device mounted to the inside of the conduit to face the first ultrasonic transmission-reception device;

a transmission-reception switch for switching the operation mode of the first and second ultrasonic transmission-reception devices between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

a calibration gas source for supplying a calibration gas, the component and the component ratio of which are known, to the conduit;

a temperature sensor, disposed in the conduit, for measuring the temperature of the calibration gas flowing through the conduit;

propagation time calculation means for calculating a first propagation time period where the ultrasonic waves propagates through the calibration gas in thee conduit on the basis of the time when the first ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the second ultrasonic transmission-reception device receives the ultrasonic waves, and a second propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the second ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the first ultrasonic transmission-reception device receives the ultrasonic waves; and

calibration means for calibrating a reference length between the first and second ultrasonic transmission-reception devices on the basis of the calculation results by the propagation time calculation means.

8. A ultrasonic apparatus for measuring a gas concentration according to claim 7 further comprising linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit;

and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

9. A ultrasonic apparatus for measuring a gas concentration according to claim 7, further comprising temperature regulating means for regulating the temperature of the conduit;

linear expansion coefficient calculating means for calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed; and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

10. A method of measuring the concentration of an objective gas by a ultrasonic gas concentration measuring apparatus which comprises, a conduit for flowing an objective gas, the concentration of which is to be measured, a first ultrasonic transmission-reception device mounted to the inside of the conduit, a second ultrasonic transmission-reception device mounted to the inside of the conduit to face the first ultrasonic transmission-reception device, and a transmission-reception switch for switching the operation mode of the first and second ultrasonic transmission-reception devices between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

the method comprising, prior to the start of the process for measuring the concentration of the gas to be measured, the steps of;

supplying a calibration gas, the component and the component ratio of which are known, to the conduit;

measuring the temperature of the calibration gas flowing through the conduit by a temperature sensor disposed in the conduit;

generating ultrasonic waves by the first ultrasonic transmission-reception device and receiving the ultrasonic waves by the second ultrasonic transmission-reception device;

switching the operation mode of the first transmission-reception device from the transmission mode to the reception mode and the operation mode of the second transmission-reception device from the reception mode to the transmission mode;

calculating a first propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the first ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the second ultrasonic transmission-reception device receives the ultrasonic waves, and a second propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the second ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the first ultrasonic transmission-reception device receives the ultrasonic waves; and

calibrating a reference length between the first and second ultrasonic transmission-reception devices on the basis of the calculation results.

11. A method according to claim 10 wherein the ultrasonic gas concentration measuring apparatus further comprising:

linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit; and

the method further comprising a steps of measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

12. (Amended) A method according to claim 10, further comprising the steps of calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed;

measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the measured temperature.

13. (Amended) A ultrasonic apparatus for measuring a gas flow rate, comprising:

a conduit for flowing an objective gas, the flow rate of which is to be measured;

a first ultrasonic transmission-reception device mounted to the inside of the conduit;

a second ultrasonic transmission-reception device mounted to the inside of the conduit to face the first ultrasonic transmission-reception device;

a transmission-reception switch for switching the operation mode of the first and second ultrasonic transmission-reception devices between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

a calibration gas source for supplying a calibration gas, the component, the component ratio and the flow rate of which are known, to the conduit;

a temperature sensor, disposed in the conduit, for measuring the temperature of the calibration gas flowing through the conduit;

propagation time calculation means for calculating a first propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the first ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the second ultrasonic transmission-reception device receives the ultrasonic waves, and a second propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the second ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the first ultrasonic transmission-reception device receives the ultrasonic waves; and

calibration means for calibrating a reference length between the first and second ultrasonic transmission-reception devices and the inner diameter of the conduit, on the basis of the calculation results by the propagation time calculation means.

14. (Amended) A ultrasonic apparatus for measuring a gas flow rate according to claim 13 further comprising linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit;

and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

15. (Amended) A ultrasonic apparatus for measuring a gas flow rate according to claim 14, further comprising temperature regulating means for regulating the temperature of the conduit;

linear expansion coefficient calculating means for calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed; and

correction means for correcting and calculating the calibrated reference length on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

16. (Amended) A method of measuring the flow rate of an objective gas by a ultrasonic gas flow rate measuring apparatus which comprises, a conduit for flowing an objective gas, the flow rate of which is to be measured, a first ultrasonic transmission-reception device mounted to the inside of the conduit, a second ultrasonic transmission-reception device mounted to the inside of the conduit to face the first ultrasonic transmission-reception device, and a transmission-reception switch for switching the operation mode of the first and second ultrasonic transmission-reception devices between a transmission mode for transmitting ultrasonic waves and a reception mode for receiving ultrasonic waves;

the method comprising, prior to the start of the process for measuring the concentration of the gas to be measured, the steps of;

supplying a calibration gas, the component and the component ratio of which are known, to the conduit;

measuring the temperature of the calibration gas flowing through the conduit by a temperature sensor disposed in the conduit;

generating ultrasonic waves by the first ultrasonic transmission-reception device and receiving the ultrasonic waves by the second ultrasonic transmission-reception device;

switching the operation mode of the first transmission-reception device from the transmission mode to the reception mode and the operation mode of the second transmission-reception device from the reception mode to the transmission mode;

calculating a first propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the first ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the second ultrasonic transmission-reception device receives the ultrasonic waves, and a second propagation time period where the ultrasonic waves propagates through the calibration gas in the conduit on the basis of the time when the second ultrasonic transmission-reception device transmits the ultrasonic waves and the time when the first ultrasonic transmission-reception device receives the ultrasonic waves; and

calibrating a reference length between the first and second ultrasonic transmission-reception devices and the inner diameter of the conduit, on the basis of the calculation results.

17. (Amended) A method according to claim 16 wherein the ultrasonic gas flow rate measuring apparatus further comprising:

linear expansion coefficient storing means for storing the linear expansion coefficient of the material forming the conduit; and

the method further comprising a steps of measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correcting and calculating the calibrated reference length and the inner diameter of the conduit, on the basis of the linear expansion coefficient and the temperature, measured by the temperature sensor, of the sample gas flowing through the conduit for the concentration measurement.

18. (Amended) A method according to claim 16, further comprising the steps of calculating the linear expansion coefficient of the material forming the conduit on the basis of the changes in the reference length when the temperature of the conduit is changed;

measuring the temperature of the sample gas flowed through the conduit for the concentration measurement; and

correcting and calculating the calibrated reference length and the inner diameter of the conduit on the basis of the linear expansion coefficient and the measured temperature.