JP2855553B2 - Transducer for ultrasonic current meter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transducer for an ultrasonic velocimeter, and more particularly to the elimination of measurement errors based on multiple reflections.

[0002]

2. Description of the Related Art As an ultrasonic current meter, a pair of transducers (1) and (2) are provided as shown in FIG. 1, and these are alternately switched by a controller (5) to excite the transducer. From the difference between the time required for the ultrasonic wave from (1) to propagate to the transducer (2) and the time required for the ultrasonic wave from the transducer (2) to propagate to the transducer (1) , Transducer (1)
(2) An ultrasonic current meter based on a so-called sing-around time difference method for measuring the flow velocity of a fluid passing through the gap is well known.

[0003] A conventional transducer (3) used in such an ultrasonic current meter is configured as shown in a sectional view of FIG. That is, a conical vibrator receiver (9) supporting the vibrator (8) is inserted into the trumpet-shaped cavity (7) at the tip of the vibrator case (6), and the vibrator (8)
The lead wire (10) is drawn out to the outside through the voids (11) and (12) of the vibrator receiver (9) and the vibrator case (6). Then, after injecting the mold resin (13) into the cavities (12) and (11), a case (1) having water-proof elasticity is provided at the vibrator-exposing opening end of the vibrator case (6).
4) For example, a synthetic rubber case is fitted by utilizing its elasticity.

[0004]

However, the above-described measurement using a current meter has a drawback that errors due to multiple reflection cannot be prevented. For example, as shown in (1) of FIG. 3 (a), the transmitted sound wave (a) from the transmitter / receiver (3a) enters the transmitter / receiver (3b). 14) Transmitter / receiver (3
a). Further, the sound wave (a ') is reflected again on the surface of the water-proof case (14) of the transducer (3a), and propagates as a sound wave (a ") to the transducer (3b). Strong reflection is caused by the opposing transducers (3a) (3
The multiple reflections are repeated between the flood protection cases (14) of (b). The transmitted sound wave (b) from the transmitter / receiver (3b)
For as shown in FIG. 3 (a) (2) is similarly so that multiple reflection occurs and transmitting sound waves of the above-mentioned transducer (3a) (a).

[0005] In the ultrasonic current meter using the sing-around time difference method, the following problems occur because the facing distance between the transducers is short. That is, (1) of FIG.
As shown in the figure, the transmitter / receiver (3b)
Immediately before the transmission of the transmitted sound wave (a), a multiple reflected sound wave (a ″) of the previous transmitted sound wave (a) is incident, or the transmitted sound wave (b) is reflected by the transmitter / receiver (3b). A sound wave (b ′) may be incident.
In (a) also, as shown in (2) of FIG. 3 (b), the sound waves (b ″) and (a ′) that are multiply reflected immediately before the transmission sound waves (b) of the transmitter / receiver (3b) are incident. May be incident.
Therefore, multiple reflected waves (a ′) (a ″) (b ′)
Depending on the level value of (b ″), there is a possibility that the multi-reflected wave is erroneously detected as the original received wave to operate, and the ultrasonic flowmeter may output an incorrect flow velocity value.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a structure of a transmitter / receiver capable of weakly degrading the level of a multiple reflection wave to a negligible level on a circuit, and to improve the measurement accuracy.

[0007]

According to the present invention, there is provided a transducer for an ultrasonic velocimeter in which a water-proof case is covered over an opening surface of an end of a vibrator case in which a vibrator is installed. The surface of the vibrator at a position facing the vibrating surface is formed as a convex curved surface, so that multiple reflected waves are scattered.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventor has clarified that the occurrence of multiple reflection in the conventional transducer as described above is due to the shape of the vibrating surface of the transducer. That is, in the conventional transducer, as shown in FIG.
Surface (141) of flood prevention case (14) directly facing 1)
Is based on the fact that it is a flat surface parallel to the vibrating surface (81) of the vibrator (8). It was made clear that measurement accuracy could be improved.

The transducer (4) according to the present invention has a cross-sectional view shown in FIG. 4 (the same reference numerals as in FIG. 2 indicate the same parts).
Vibration surface (81) of vibrator (8) of flood prevention case (15)
Is formed in a convex curved surface having a so-called R on the surface (151) at a position directly opposite to. With this configuration, by appropriately selecting the curved surface R, other incident sound waves, that is, most of the multiple reflected waves, except for the reflected sound waves necessary for measurement near the center of the vibrating surface of the vibrator (8), As shown by the dotted line in FIG. 5, the water-proof case (15) can be reflected on the convex surface (151) of the water-proof case and scattered out of the vibration plane of the other transducer.
Therefore, the level of the multiple reflected waves incident on the transducers (3a) and (3b) can be weakly degraded to a value that can be ignored in the operation of the circuit.
Measurement errors due to multiple reflections can be significantly reduced. According to an experiment, when a curved surface of the surface (151) of the water-proof case (15) is given a radius of 50 mm in a transducer with an outer diameter of 30 mm, the measurement error is reduced to about 1/10 of that of the conventional structure.
I was able to.

[0010]

As described above, according to the present invention, the propagation level of the multiple reflection wave which causes a measurement error can be reduced by changing the shape of the watertight case covering the vibrating surface portion of the ultrasonic flowmeter transmitter / receiver. It is clear that it can be weakly degraded and significantly contributes to the improvement of the measurement accuracy of the ultrasonic anemometer.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the measurement principle of an ultrasonic current meter.

FIG. 2 is a structural diagram of a conventional transducer.

FIG. 3 is an explanatory diagram of generation of multiple reflected waves.

FIG. 4 is a structural diagram of the transducer of the present invention.

FIG. 5 is a diagram illustrating a reflection state of a sound wave in the transducer of the present invention.

[Explanation of symbols]

1, 2, 3, 4 Transmitter / receiver for ultrasonic current meter 5 Controller 6 Transducer case 7 Trump-shaped cavity 8 Transducer 9 Conical transducer receiver 10 Lead wire 11, 12 Void 13 Mold resin 14, 15 Waterproof case 81 Vibration surface of vibrator 141, 151 Surface at position facing vibration surface of vibrator of watertight case

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01P 5/00 G01F 1/66

Claims (1)

(57) [Claims] 1. A transducer for use in an ultrasonic current meter of a sing-around time-difference type in which an elastic water-proof case is covered on an opening surface of a vibrator case on which a vibrator is installed and closed. That the surface at the position facing the vibrating surface of the vibrator of the use case is formed as a convex curved surface having a central portion having a maximum thickness so as to suppress the influence of multiple reflection. > Featured transducer for ultrasonic current meter.