JP3453576B2 - Ultrasonic flow meter - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to ultrasonic flowmeters.

[0002]

2. Description of the Related Art As an example of a conventional ultrasonic flowmeter, a vortex generator that generates a Karman vortex is arranged in a pipe in which a fluid flows, and an ultrasonic wave is sent to a downstream portion of the vortex generator in the pipe.・
There is an ultrasonic flowmeter in which receivers are arranged opposite to each other and a drive circuit for driving the ultrasonic transmitter is connected to the ultrasonic transmitter. This ultrasonic flowmeter utilizes the fact that the ultrasonic waves from the ultrasonic transmitter are modulated by the Karman vortex according to the flow velocity and the modulated ultrasonic waves are received by the ultrasonic receiver. Is calculated to obtain the flow velocity of the fluid and thus the flow rate.

[0003]

By the way, in the above-described ultrasonic flowmeter, the characteristics of the ultrasonic transmitter / receiver may change due to the influence of temperature, pressure, etc., which allows stable measurement. It could happen that you can't do it. The ultrasonic transmitter / receiver is sensitive to temperature, for example -20 ° C.
In the following low temperature environment, the efficiency is lowered, and there is a possibility that ultrasonic wave transmission / reception cannot be performed properly. That is, as the temperature decreases, the mechanical loss of the ultrasonic transmitter that emits ultrasonic waves increases, and the electromechanical conversion efficiency and the transmission efficiency from the ultrasonic transmitter to the fluid decrease, which results in the ultrasonic transmitter. When the ultrasonic transmitter is driven with a constant voltage, the energy input to the ultrasonic transmitter becomes small and the radiation efficiency decreases. In this case, if the fluid is a gas, the above-mentioned problem becomes remarkable because the transmission efficiency from the ultrasonic transmitter to the gas is low.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an ultrasonic flowmeter capable of stably measuring the flow rate of gas even when the temperature is lowered.

[0005]

According to a first aspect of the present invention, there is provided an ultrasonic wave transmitter / receiver provided in a pipe through which a gas flows, and a driving voltage is applied to the ultrasonic wave transmitter to realize the ultrasonic wave transmitter. In an ultrasonic flowmeter having driving means for driving, a current detection circuit is interposed between the ultrasonic transmitter and the driving means, and the amplitude of the drive voltage is adjusted based on a detection signal of the current detection circuit. A drive voltage regulator is installed to drive the drive voltage from the drive means.
And the ultrasonic transmitter's error based on the detection signal of the current detection circuit.
Impedance, and adjust the drive voltage according to the detection result.
A regulator control means for controlling the regulator is provided .

According to the second aspect of the present invention, there is provided an ultrasonic wave transmitter / receiver provided in a gas passage, and drive means for applying a drive voltage to the ultrasonic wave transmitter to drive the ultrasonic wave transmitter. In the provided ultrasonic flowmeter, a current detection circuit is interposed between the ultrasonic transmitter and the driving means, and an impedance matching circuit for adjusting and setting the output impedance of the driver is provided between the driver and the ultrasonic transmitter. A matching circuit control means is provided which detects the impedance of the ultrasonic transmitter based on the drive voltage from the drive means and the detection signal of the current detection circuit and controls the impedance matching circuit according to the detection result. Characterize.

[0007]

According to the structure of claim 1, the driving voltage regulator can be set to control the driver so as to increase the amplitude of the driving voltage when the current input to the ultrasonic transmitter becomes small. By setting in this way, when the temperature is lowered and the impedance of the ultrasonic transmitter is large, and when the current input to the ultrasonic transmitter is small, the amplitude of the drive voltage becomes large. Therefore, the energy input to the ultrasonic transmitter is increased, and the radiation efficiency of the ultrasonic transmitter and the transmission efficiency from the ultrasonic transmitter to the gas are improved. It
In addition, when the impedance of the ultrasonic transmitter exceeds a predetermined value, the drive voltage amplitude can be increased, and when the impedance is below the predetermined value, the drive voltage amplitude can be decreased. By controlling in this way, the amplitude of the drive voltage increases due to the impedance of the ultrasonic transmitter increasing when the temperature decreases.
Therefore, the energy input to the ultrasonic transmitter is increased, and the radiation efficiency of the ultrasonic transmitter and the transmission efficiency from the ultrasonic transmitter to the gas are improved. Further, when the temperature rises and the electrical impedance becomes less than a predetermined value due to this,
Reduce the amplitude of drive voltage.

According to the structure of claim 2 , the output impedance of the driving means can be adjusted so as to be equal to the input impedance of the ultrasonic transmitter, and by setting in this way, the output of the driver of the driving means. The characteristic that the energy input to the ultrasonic transmitter from the driver is maximized is ensured when the impedance and the input impedance of the ultrasonic transmitter are equal, and if the impedance of the ultrasonic transmitter decreases by temperature. As a result, a large amount of energy is input to the ultrasonic transmitter. Therefore, the radiation efficiency of the ultrasonic transmitter and the transmission efficiency from the ultrasonic transmitter to the gas are improved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An ultrasonic flowmeter according to a first embodiment of the present invention will be described below with reference to FIG. 2 and with reference to FIG. Figure 1
Ultrasonic flow including items common to the ultrasonic flowmeter of the first embodiment
It is a flowmeter, and for convenience, first, the ultrasonic flowmeter (reference
Example) will be described. In FIG. 1 , a vortex generator 2 that generates a Karman vortex having a frequency corresponding to the flow velocity and thus the flow rate is arranged in a pipe 1 through which gas flows. An ultrasonic transmitter 3 and an ultrasonic receiver 4 are arranged in the tube 1 so as to face each other so as to face the Karman vortex generation region. Driving means 5 is connected to the ultrasonic transmitter 3.

The driving means 5 comprises an oscillation circuit 6 and a driver 7. The oscillator circuit 6 outputs an oscillation signal of a predetermined frequency to the driver 7. The driver 7 applies the drive voltage D having the same phase as that of the oscillation signal to the ultrasonic transmitter 3 to drive the ultrasonic transmitter 3. In this case, the driver 7 can change the amplitude of the drive voltage D. The ultrasonic transmitter 3 receives the driving voltage D and emits ultrasonic waves into the gas.

A vortex signal detector 8 is provided so as to be connected to the ultrasonic receiver 4 and the oscillating circuit 6, and the amount of modulation of the ultrasonic waves emitted by the ultrasonic transmitter 3 due to the Karman vortex is obtained,
Vortex signal K corresponding to the flow velocity of the gas in the pipe 1, and thus the flow rate
Is output to a terminal 9 connected to a display, a printer or the like (not shown).

Between the ultrasonic transmitter 3 and the driver 7,
The current detector 10 is interposed, detects the current flowing through the ultrasonic transmitter 3, and outputs the detection signal. A drive voltage adjuster 11 is connected to the current detector 10, and controls the driver 7 according to the detection signal to adjust the amplitude of the drive voltage D. In this case, the driver 7 is controlled so that the amplitude is increased when the value of the detection signal is small.

The ultrasonic flowmeter of FIG. 1 configured as described above
Then, when the temperature of the gas or the surroundings decreases, the mechanical loss of the ultrasonic transmitter 3 increases, the electromechanical conversion efficiency and the transmission efficiency from the ultrasonic transmitter 3 to the gas decrease, and the ultrasonic transmitter 3 The electrical impedance of is increased. Then, the current value input to the ultrasonic transmitter 3 becomes small.
In response to the decrease in the current value, the drive voltage adjuster 11 controls the driver 7 to increase the amplitude of the drive voltage D. As the amplitude of the drive voltage D increases, the energy input to the ultrasonic transmitter 3 increases,
The radiation efficiency of the ultrasonic transmitter 3 and the transmission efficiency from the ultrasonic transmitter 3 to the gas are improved. Therefore, the proper flow rate measurement can be performed even when the temperature drops.

In contrast to the ultrasonic flowmeter of FIG. 1 described above, the ultrasonic flowmeter of the first embodiment of the present invention is as shown in FIG.
In addition, the driver 7, the current detector 10 and the drive voltage regulator 1
A regulator control means 12 is provided in connection with 1. The regulator control means 12 obtains the electrical impedance of the ultrasonic transmitter 3 by dividing the amplitude of the drive voltage D from the driver 7 by the current detected by the current detector 10, and this impedance becomes equal to or higher than a predetermined value. When it becomes less, the drive voltage adjuster 11 is controlled to increase the amplitude of the drive voltage D output from the driver 7, and when it becomes less than a predetermined value, the drive voltage adjuster 11 is controlled. The amplitude of the drive voltage D is reduced.

In this ultrasonic flowmeter, when the temperature of gas or the like is lowered and the electrical impedance of the ultrasonic transmitter 3 becomes equal to or higher than a predetermined value, the amplitude of the drive voltage D is increased. Then, the energy input to the ultrasonic transmitter 3 is increased, the radiation efficiency and the transmission efficiency from the ultrasonic transmitter 3 to the gas in the pipe 1 (see FIG. 1) are improved, and even when the temperature drops, the energy is appropriate. The flow rate can be measured. Further, when the temperature of gas or the like rises and the electrical impedance becomes less than a predetermined value accordingly, the amplitude of the drive voltage D is maintained with the amount of ultrasonic waves emitted from the ultrasonic transmitter 3 maintained at a desired amount. To reduce. Therefore, at room temperature to high temperature, the current flowing through the ultrasonic transmitter 3, that is, the consumed current is reduced, and the energy saving effect of the entire device can be improved.

In the above embodiment, the driving means 5 is composed of the oscillation circuit 6 and the driver 7, but the present invention is not limited to this, and the driving voltage D having a predetermined frequency is used. May be output and the amplitude of the drive voltage D can be adjusted to configure the drive means.

Next, an ultrasonic flowmeter according to a second embodiment of the present invention will be described based on FIG. 3 and with reference to FIG. The driver 7 of the third embodiment outputs a driving voltage D having a predetermined frequency, but unlike the drivers 7 of the first and second embodiments,
The amplitude of the drive voltage D is not adjusted. Figure 3
In FIG. 3, an impedance matching circuit 13 that adjusts and sets the output impedance of the driver 7 is interposed between the driver 7 and the current detector 10. Matching circuit control means 14 is provided in connection with the impedance matching circuit 13, the driver 7 and the current detector 10. The matching circuit control means 14 obtains the input impedance of the ultrasonic transmitter 3 by dividing the amplitude of the drive voltage D from the driver 7 by the current detected by the current detector 10, and the output impedance of the driver 7 is the input impedance. Set a constant to be equivalent to. Here, due to the circuit configuration, generally, the energy input from the driver 7 to the ultrasonic transmitter 3 becomes the maximum value when the output impedance of the driver 7 and the input impedance of the ultrasonic transmitter 3 are equal. It has been known.

In this ultrasonic flowmeter, the constant is set so that the output impedance of the driver 7 becomes equal to the input impedance of the ultrasonic transmitter 3 as described above.
Even if the impedance of the ultrasonic transmitter 3 increases as the temperature decreases, a large amount of energy is input to the ultrasonic transmitter 3. For this reason, the radiation efficiency of the ultrasonic transmitter 3 and the transmission efficiency from the ultrasonic transmitter 3 to the gas in the pipe 1 (see FIG. 1) are improved, and proper flow rate measurement can be performed even when the temperature drops. . Although the driving means 5 is composed of the oscillation circuit 6 and the driver 7 as an example, the driving means may be configured to output the driving voltage D having a predetermined frequency.

[0019]

According to the invention of claim 1, the driving voltage regulator is set to control the driver so as to increase the amplitude of the driving voltage when the current inputted to the ultrasonic transmitter becomes small. As a result, when the temperature drops and the impedance of the ultrasonic transmitter becomes large, and when the current input to the ultrasonic transmitter becomes small, the amplitude of the drive voltage increases and the energy input to the ultrasonic transmitter increases. ,
Since the radiation efficiency of the ultrasonic transmitter and the transmission efficiency from the ultrasonic transmitter to the gas are improved, proper flow rate measurement can be performed even when the temperature drops. Further, when the impedance of the ultrasonic transmitter exceeds a predetermined value, the drive voltage amplitude is increased, while when it is less than the predetermined value, the drive voltage amplitude is controlled to be reduced. As a result, when the temperature drops, the impedance of the ultrasonic transmitter increases, so that the amplitude of the drive voltage increases, the energy input to the ultrasonic transmitter increases, and the radiation of the ultrasonic transmitter increases. Since the efficiency and the efficiency of the transmission from the ultrasonic transmitter to the gas are improved, the proper flow rate measurement can be performed even when the temperature drops. Further, when the temperature rises and the electrical impedance becomes less than a predetermined value accordingly, the amplitude of the driving voltage is reduced, so that the current flowing through the ultrasonic transmitter at room temperature or high temperature, that is, the consumed current is small. Therefore, the energy saving effect of the entire device can be improved.

According to the second aspect of the present invention, the output impedance of the driving means is set to be equal to the input impedance of the ultrasonic transmitter, so that the impedance of the ultrasonic transmitter temporarily changes with a decrease in temperature. Even if it becomes large, a large amount of energy is input to the ultrasonic transmitter, and the radiation efficiency of the ultrasonic transmitter and the transmission efficiency from the ultrasonic transmitter to the gas are improved, so that proper flow rate measurement can be performed even when the temperature drops. You can do it.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the first and second embodiments of the present invention .
It is a figure which shows the ultrasonic flowmeter as an example typically.

FIG. 2 is a diagram schematically showing the ultrasonic flowmeter according to the first embodiment of the present invention.

FIG. 3 is a diagram schematically showing an ultrasonic flowmeter according to a second embodiment of the present invention.

[Explanation of symbols]

1 tube 3 Ultrasonic transmitter 4 Ultrasonic receiver 5 Drive means 7 driver 10 Current detector 11 Drive voltage regulator 12 Regulator control means 13 Impedance matching circuit 14 Matching circuit control means

Front page continuation (72) Inventor Atsuro Sensen 4-1-2, Hirano-cho, Chuo-ku, Osaka City Osaka Osaka Gas Co., Ltd. (72) Inventor Yutaka Inada 1-3-6 Fujimi, Kawasaki-ku, Kanagawa Prefecture Tokiko Incorporated (72) Inventor Hiroshi Yoshikura 1-3-6 Fujimi, Kawasaki-ku, Kawasaki, Kanagawa Tokiko Ltd. (56) Reference JP-A-51-214953 (JP, A) JP-A-5-38343 ( (58) Fields investigated (Int.Cl. ⁷ , DB name) G01F 1/00-9/02

Claims (2)

(57) [Claims] 1. An ultrasonic flow rate, comprising: an ultrasonic transmitter / receiver provided in a pipe through which gas flows; and a drive means for applying a drive voltage to the ultrasonic transmitter to drive the ultrasonic transmitter. In the meter, a current detection circuit is provided between the ultrasonic transmitter and the drive means, and a drive voltage adjuster for adjusting the amplitude of the drive voltage based on the detection signal of the current detection circuit is provided .
Based on the drive voltage from the stage and the detection signal of the current detection circuit
The impedance of the ultrasonic transmitter is detected by
Adjuster control means to control the drive voltage adjuster according to
An ultrasonic flow meter characterized by being struck . 2. An ultrasonic flow rate, comprising: an ultrasonic transmitter / receiver provided in a gas flow path; and drive means for applying a drive voltage to the ultrasonic transmitter to drive the ultrasonic transmitter. In the meter, a current detection circuit is provided between the ultrasonic transmitter and the driving means, and an impedance matching circuit that adjusts and sets the output impedance of the driver is provided between the driver and the ultrasonic transmitter to drive the An ultrasonic wave characterized in that a matching circuit control means is provided for detecting the impedance of the ultrasonic transmitter based on the drive voltage and the detection signal of the current detection circuit from the means and controlling the impedance matching circuit according to the detection result. Flowmeter.