Ultrasonic flowmeter and ultrasonic flow rate measuring method

• US 20050072248A1
• Filed: 10/29/2003
• Published: 04/07/2005
• Est. Priority Date: 11/26/2002
• Status: Active Grant

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Suginouchi, Takehiko, Hashimoto, Masahiko
• Granted Patent: US 7,073,395 B2
• Time in Patent Office: Days
• US Class Current: 73/861.270
• CPC Class Codes: G01F 1/66 by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
• 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

Abstract

An ultrasonic flowmeter of the present invention includes: first and second ultrasonic transducers that send and receive an ultrasonic wave and are arranged so as to form a propagation path for the ultrasonic wave in a flow path of fluid; a transmission unit and a reception unit that drive the first ultrasonic transducer and the second ultrasonic transducer such that the ultrasonic wave is sent and received in two ways between the first ultrasonic transducer and the second ultrasonic transducer, and receive the ultrasonic wave; a zero-cross detection unit that measures a propagation time of the ultrasonic wave by subjecting a received signal generated by the ultrasonic wave received in the reception unit to zero-cross detection; and a correction unit that reduces an error in the zero-cross detection caused by noise superimposed on the received signal, in which the ultrasonic flowmeter calculates a flow volume of the fluid on the basis of the propagation time.

Claims

1. An ultrasonic flowmeter comprising:

first and second ultrasonic transducers that send and receive an ultrasonic wave and are arranged so as to form a propagation path for the ultrasonic wave in a flow path of fluid;

a transmission unit and a reception unit that drive the first ultrasonic transducer and the second ultrasonic transducer such that the ultrasonic wave is sent and received in two ways between the first ultrasonic transducer and the second ultrasonic transducer, and receive the ultrasonic wave;

a zero-cross detection unit that measures a propagation time of the ultrasonic wave by subjecting a received signal generated by the ultrasonic wave received in the reception unit to zero-cross detection; and

a correction unit that reduces an error in the zero-cross detection caused by noise superimposed on the received signal,

wherein the ultrasonic flowmeter calculates a flow volume of the fluid on the basis of the propagation time.

2. The ultrasonic flowmeter according to claim 1,

wherein the correction unit corrects the flow volume of the fluid on the basis of a magnitude of amplitude of the received signal.

3. The ultrasonic flowmeter according to claim 2,

wherein the correction unit includes:

a level detection unit that measures amplitude of a predetermined wave of the received signal; and

a correction data storage unit that stores data indicating a relation between the amplitude of the predetermined wave and the propagation time of the received signal, and

the correction unit corrects the propagation time according to a magnitude of the amplitude of the predetermined wave on the basis of the data.

4. The ultrasonic flowmeter according to claim 2,

wherein the ultrasonic flowmeter receives an ultrasonic wave plural times in one of the first ultrasonic transducer and the second ultrasonic transducer with a sing around method,

the correction unit includes:

a level detection unit that measures amplitudes of predetermined waves of plural received signals generated by receiving the ultrasonic wave plural times, respectively;

a level average unit that calculates an average of magnitudes of the amplitudes of the plural received signals; and

a correction data storage unit that stores data indicating a relation between the amplitudes of the predetermined waves and the propagation time of the received signals, and the correction unit corrects the propagation time according to the average of the magnitudes of the amplitudes on the basis of the data.

5. The ultrasonic flowmeter according to claim 1,

wherein the zero-cross detection unit has a comparator for finding a zero-cross point, and

the correction unit corrects the flow volume of the fluid on the basis of the number of times of chattering of the comparator that is caused when the received signal is subjected to the zero-cross detection.

6. The ultrasonic flowmeter according to claim 5,

wherein the correction unit includes:

a counter that measures the number of times of chattering; and

a correction data storage unit that stores data indicating a relation between the number of times of chattering and a propagation time, and

the correction unit corrects the propagation time according to the number of times of chattering on the basis of the data.

7. The ultrasonic flowmeter according to claim 1,

wherein, depending upon whether the zero-cross detection for the received signal is performed at a falling edge of a signal or a rising edge of a signal, the correction unit uses a voltage set to a negative or positive value as a reference voltage for the zero-cross detection.

8. The ultrasonic flowmeter according to claim 1,

wherein the ultrasonic flowmeter receives an ultrasonic wave plural times in one of the first ultrasonic transducer and the second ultrasonic transducer with the sing around method, and

the correction unit offsets a reference voltage for performing the zero-cross detection for the next received signal on the basis of a magnitude of amplitude of an immediately preceding received signal among plural received signals generated by receiving the ultrasonic wave plural times.

9. The ultrasonic flowmeter according to claim 8,

wherein the correction unit includes:

a level detection unit that measures amplitude of a predetermined wave of the immediately preceding received signal; and

a correction data storage unit that stores data indicating a relation between amplitude of a wave of the received signal and a reference voltage for performing the zero-cross detection, and the correction unit calculates a value of the reference voltage according to a magnitude of the amplitude on the basis of the data.

10. The ultrasonic flowmeter according to claim 8,

wherein the correction unit includes:

an integration unit that calculates a value obtained by integrating a rising edge part of the immediately preceding received signal for a predetermined time; and

a correction data storage unit that store data indicating a relation between the integrated value and a reference voltage for performing the zero-cross detection, and the correction unit calculates a value of the reference voltage according to a magnitude of the integrated value on the basis of the data.

11. The ultrasonic flowmeter according to claim 3,

wherein the predetermined wave of the received signal is a wave subjected to the zero-cross detection.

12. A gas meter comprising the ultrasonic flowmeter defined in claim 1.

13. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave from a first ultrasonic transducer to fluid and receiving the ultrasonic wave in a second ultrasonic transducer;

measuring a propagation time of the ultrasonic wave by subjecting a received signal generated by the received ultrasonic wave to zero-cross detection;

measuring amplitude of the received signal; and

correcting the propagation time on the basis of the amplitude of the received signal.

15. The flow volume measurement method by an ultrasonic wave according to claim 13,

wherein the step of measuring amplitude measures amplitude of a wave of a received signal subjected to the zero-cross detection.

20. A computer readable recording medium having recorded therein a program for causing a computer to execute the respective steps defined in the flow volume measurement method by an ultrasonic wave according to claim 13.

14. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave plural times from a first ultrasonic transducer to fluid and receiving the ultrasonic wave plural times in a second ultrasonic transducer with a sing around method;

measuring a propagation time of the ultrasonic wave, which is received plural times, by subjecting plural received signals due to the ultrasonic wave received plural times to zero-cross detection;

measuring amplitudes of the plural received signals; and

calculating an average value of the amplitudes of the plural received signals and correcting the propagation time on the basis of the average value.

16. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave from a first ultrasonic transducer to fluid and receiving the ultrasonic wave in a second ultrasonic transducer;

measuring a propagation time of the ultrasonic wave by subjecting a received signal generated by the received ultrasonic wave to zero-cross detection;

measuring the number of times of chattering of a comparator that occurs at the time of the zero-cross detection; and

correcting the propagation time on the basis of the number of times of chattering.

17. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave from a first ultrasonic transducer to fluid and receiving the ultrasonic wave in a second ultrasonic transducer;

measuring a propagation time of the ultrasonic wave by subjecting a received signal generated by the received ultrasonic wave to zero-cross detection; and

calculating a flow volume of the fluid on the basis of the propagation time,

wherein the flow volume measurement method sets a reference potential for the zero-cross detection set to a negative voltage or a positive voltage depending upon whether the zero-cross detection is performed at a rising edge of a signal or a falling edge of a signal.

18. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave from a first ultrasonic transducer to fluid and receiving the ultrasonic wave in a second ultrasonic transducer;

measuring amplitude of a received signal generated by the received ultrasonic wave; and

measuring a propagation time of the ultrasonic wave by subjecting the received signal to zero-cross detection,

wherein the flow volume measurement method repeats the reception step, the amplitude measurement step, and the propagation time measurement step with a sing around method and offsets a reference voltage for performing the zero-cross detection for the next received signal on the basis of a magnitude of the amplitude of the received signal measured in the amplitude measurement step.

19. A flow volume measurement method by an ultrasonic wave that measures a flow volume of fluid on the basis of a propagation time difference of an ultrasonic wave, comprising the steps of:

sending an ultrasonic wave from a first ultrasonic transducer to fluid and receiving the ultrasonic wave in a second ultrasonic transducer;

calculating a value obtained by integrating a rising edge part of a received signal generated by the received ultrasonic wave for a predetermined time; and

measuring a propagation time of the ultrasonic wave by subjecting the received signal to zero-cross detection,

wherein the flow volume measurement method repeats the reception step, the step of calculating an integrated value, and the propagation time measurement step with a sing around method and offsets a reference voltage for performing the zero-cross detection for the next received signal on the basis of the integrated value of the received signal calculated in the step of calculating an integrated value.