JP2004028994A5

JP2004028994A5 -

Info

Publication number: JP2004028994A5
Application number: JP2003070497A
Authority: JP
Filing date: 2003-03-14
Publication date: 2005-03-17

Claims

First and second ultrasonic transducers that transmit and receive ultrasonic waves and are arranged to form a propagation path of the ultrasonic waves in a fluid flow path;
A transmitter for driving one of the first and second ultrasonic transducers;
A first matching unit connected to the transmission unit and adjusting an output impedance of the transmission unit;
A receiver that has an input impedance smaller than the adjusted output impedance and receives an ultrasonic wave that has reached the other of the first and second ultrasonic transducers; An ultrasonic flowmeter that measures the flow rate of fluid by detecting the two-way propagation time difference of sound waves.

2. The ultrasonic flow rate according to claim 1, wherein the adjusted output impedance is larger than ½ of an impedance value that one of the first and second ultrasonic transducers has at a resonance frequency. Total.

The ultrasonic flowmeter according to claim 2, wherein the adjusted output impedance is substantially equal to an impedance value of one of the first and second ultrasonic transducers.

The ultrasonic flowmeter according to claim 1, wherein the input impedance is 40Ω or less.

The ultrasonic flowmeter according to claim 1, wherein the input impedance is 20Ω or less.

The ultrasonic flowmeter according to claim 1, further comprising a reflected wave detection unit for detecting a reflected wave generated due to impedance mismatch between the first or second ultrasonic transducer and the transmission unit.

The ultrasonic flowmeter according to claim 6, further comprising a directional coupler for selectively guiding a reflected wave to the reflected wave detection unit.

The ultrasonic flowmeter according to claim 6, further comprising a control unit that controls the first matching unit based on a reflected wave detected by the reflected wave detection unit.

Any of the first switching unit, the receiving unit, and the first and second ultrasonic transducers that selectively connect the first matching unit and any of the first and second ultrasonic transducers. The ultrasonic flowmeter according to claim 1, further comprising a second switching unit that selectively connects the heels.

The ultrasonic flowmeter according to claim 9, wherein the first matching unit is adjusted so that the output impedance substantially matches an impedance at a resonance frequency of the ultrasonic transducer selected by the switching unit.

A second matching unit that adjusts an output impedance of the transmission unit; a first switching unit that selectively connects the transmission unit to one of the first matching unit and the second matching unit; and the reception And a second switching unit that selectively connects the first and second ultrasonic transducers to each other, and the first and second matching units are respectively the first and second matching units. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is connected to an ultrasonic transducer.

The ultrasonic flowmeter according to claim 11, wherein the first and second matching sections are adjusted so that the output impedance substantially matches the impedance at the resonance frequency of the first and second ultrasonic transducers. .

The ultrasonic flowmeter according to claim 1, wherein the first and second ultrasonic vibrators vibrate in a thickness vibration mode.

The ultrasonic flow rate according to any one of claims 1 to 13, further comprising a detection unit for detecting a reception signal amplified by the reception unit, wherein the arrival time of the reception signal is determined by a zero cross point in the detection unit. Total.

And a detection unit configured to detect the reception signal amplified by the reception unit, wherein the detection unit sets a plurality of zero cross points in the reception signal, and corrects the flow rate using the plurality of zero cross points. Item 15. The ultrasonic flowmeter according to Item 14.

The ultrasonic flowmeter according to any one of claims 1 to 15, which is provided in a flow path through which gas flows;
A shut-off valve for shutting off a gas flowing through the flow path;
A control device for controlling the ultrasonic flowmeter and the shutoff valve;
Gas meter equipped with.

A transmission unit for forming the ultrasound propagation path flow path of the fluid, to drive one of the pair of ultrasonic transducers using a pair of ultrasonic transducers as transmitters and receivers, said transmission A receiving unit that has an input impedance smaller than the output impedance of the unit and receives the ultrasonic wave that has reached the other of the pair of ultrasonic transducers, and propagates the ultrasonic wave bidirectionally along the propagation path. A method of measuring the flow rate of a fluid by detecting the two-way propagation time difference.

The output impedance of the transmitter is adjusted so as to be at least a half or more of the impedance at the resonance frequency of the ultrasonic transducer used as a transmitter, and the input impedance of the receiver for receiving the ultrasonic The method for measuring the flow rate of the fluid according to claim 17, wherein the flow rate is set to be equal to or less than a value of an output impedance of the transmission unit.

19. The method for measuring a fluid flow rate according to claim 18, wherein the output impedance of the transmitter is adjusted to be substantially equal to an impedance value at a resonance frequency of the ultrasonic transducer used as a transmitter.

The method for measuring a fluid flow rate according to claim 18, wherein an input impedance of the receiving unit is set to 40Ω or less.

The method for measuring a fluid flow rate according to claim 18, wherein an input impedance of the receiving unit is set to 20Ω or less.

19. The fluid flow rate according to claim 18, wherein a reflected wave generated by impedance mismatch between the pair of ultrasonic transducers and the transmitting unit is detected, and an output impedance of the transmitting unit is adjusted so that the reflected wave becomes small. How to measure.

First and second ultrasonic transducers that transmit and receive ultrasonic waves and are arranged to form a propagation path of the ultrasonic waves in a fluid flow path;
  A transmitter for driving one of the first and second ultrasonic transducers;
  A first matching unit connected to the transmission unit and adjusting an output impedance of the transmission unit to be substantially equal to one impedance value of the first and second ultrasonic transducers;
  A receiving unit that receives an ultrasonic wave having an input impedance that is substantially equal to or smaller than the adjusted output impedance and that has reached the other of the first and second ultrasonic transducers An ultrasonic flowmeter that measures the flow rate of fluid by detecting a two-way propagation time difference of ultrasonic waves propagating between the propagation paths.

A transmitter for forming an ultrasonic wave propagation path in a fluid flow path using a pair of ultrasonic transducers as a transmitter and a receiver, and driving one of the pair of ultrasonic transducers, and the transmission A matching unit that adjusts the output impedance of the transmitter to be substantially equal to the impedance value of the ultrasonic transducer used as a transmitter, and the output impedance of the transmitter is approximately equal to the output impedance of the transmitter Bidirectional propagation by propagating ultrasonic waves bidirectionally along the propagation path using a receiving unit having a smaller input impedance and receiving ultrasonic waves that have reached the other of the pair of ultrasonic transducers A method of measuring the flow rate of fluid by detecting the time difference.