JP2000346686A - Ultrasonic flowmeter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic flowmeter in which the bypass means of an ultrasonic signal is installed and in which a circuit-delay-time measuring means and a flow-velocity correction and computing means are provided. SOLUTION: This flowmeter is provided with an ultrasonic sensor 1A and an ultrasonic sensor 1B which are tilted with reference to the flow direction of a fluid and which are arranged in such a way that their transmission side faces their reception side. The flowmeter is provided with a transmission means 2 which excites the ultrasonic sensor 1A (1B) on one side and which transmits an ultrasonic signal 1a from the upstream side or the downstraem side. The flowmeter is provided with a time measuring means 3 in which the ultrasonic signal 1a propagated in the fluid is detected by the ultrasonic sensor 1B (1A) on the other side and by which the propagation time of the ultrasonic signal 1a to the downstream direction and the upstream direction is measured. The flowmeter is provided with a flow-rate computing means 4 by which the flow velocity F or the flow rate of the fluid is computed on the basis of the propatation time. Then, a bypass means 5 which bypasses a part between the transmission-side ultrasonic sensor 1A (1B) and the reception-side ultrasonic sensor 1B (1A) and which transfers an electric signal to the time measuring means 3 from the transmission means 2 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic flowmeter for measuring a flow rate of a fluid by an ultrasonic method, and more particularly to an ultrasonic flowmeter for correcting a delay time between circuits from transmission of an ultrasonic signal to detection of a propagation time. It relates to a flow meter.

[0002]

2. Description of the Related Art FIG. 4 is a layout diagram of a general ultrasonic sensor relating to an ultrasonic flowmeter of the prior art and the present invention. still,
For simplicity of description, the ultrasonic signal 1a will be mainly described below in the direction from the upstream side to the downstream side, and the reverse direction will be indicated by parenthesized signs as necessary. Ultrasonic flow meter is an ultrasonic transducer
The ultrasonic sensors 1A and 1B consisting of
The angle between the flow direction of the fluid 14 and the flow direction of the fluid 14 in the measuring pipe 13 shown in FIG. It is configured to be deployed facing.

In FIG. 5, one ultrasonic sensor, for example, an ultrasonic sensor 1A (1B) is excited, and an ultrasonic signal 1a is transmitted from the upstream side (downstream side) to the flow of the fluid 14. In the illustrated example, the transmitting unit 2 represented by the transmitting unit 21 and the ultrasonic signal propagating in the fluid 14 by the other ultrasonic sensor 1B (1A)
1a, and the propagation time T3 of the ultrasonic signal 1a is detected.
Propagation time T3d of the ultrasonic signal 1a in the downstream direction (upstream direction),
In the illustrated example for measuring (T3u) (hereinafter, when the division is performed including the propagation direction, the division is made by the subscripts of d and u), the time measuring means 3 including the receiving unit 31/32 and the time measuring unit 33, Flow rate calculation means 4 comprising a calculation device 41 such as a microcomputer for calculating the flow velocity F or flow rate of the fluid 14 from the propagation times T3d, T3u of the
And is provided.

With this configuration, the flow velocity F of the fluid 14 can be detected and calculated as described below. FIG.
, The transmission means 2 emits a timing signal 2a at a predetermined constant interval, generates an excitation pulse 2b for the ultrasonic sensor 1 in the transmission unit 21, and generates a switch SW1 (not shown).
Excites the upstream sensor 1A selected in step (1). The upstream sensor 1A excited by the excitation pulse 2b generates an ultrasonic signal 1a having a natural frequency determined by the electro-mechanical system of the ultrasonic sensor 1, and this ultrasonic signal 1a Propagating through 14 and received by the downstream sensor 1B and converted into an electric signal 3a. The received electric signal 3a is amplified by the receiving unit 31 via a switch SW2 (not shown), passes through the band-pass filter 32, passes the main frequency component of the natural frequency generated by the ultrasonic sensor 1, and receives the signal. The electrical and acoustic noise components included in the signal 3a are removed. The output 3b of the band-pass filter 32 from which the noise component has been removed is compared with a predetermined reference value by the time measurement unit 33, and the reception signal 3c is output as the time t3 when the ultrasonic signal 1a was received.

The time measuring section 33 compares the time t1 (timing signal 2a) at which the transmitting means 2 excites the ultrasonic sensor 1A with the reference value, and compares the time t1 with the reference value to generate an ultrasonic signal.
Propagation time T3 (T3 (T3) of the ultrasonic signal 1a from the upstream side to the downstream
d) can be calculated.

Next, in measuring the propagation time T3 of the ultrasonic signal 1a, the switches SW1 and SW2 are switched by the next timing signal 2a to propagate the ultrasonic signal 1a from the downstream sensor 1B to the upstream sensor 1A. Then, the propagation time T3 (T3u) of the ultrasonic signal 1a from the downstream side to the upstream side (upstream direction) is calculated. By alternately switching these switches SW1 and SW2, the propagation time T3d of the ultrasonic signal 1a in the downstream direction and the propagation time T3u of the ultrasonic signal 1a in the upstream direction can be measured. T3d and T3u are subjected to arithmetic processing by an arithmetic unit 41 composed of a microcomputer or the like, and the flow rate F of the fluid 14 is calculated.
Alternatively, the flow rate can be determined.

In FIG. 4, the speed of sound in the fluid 14 is V,
Assuming that the flow velocity of F is F, the propagation times T1 of the ultrasonic signal 1a in the measurement tube 13 in the downstream and upstream directions are respectively (T1d, T1
1u), the flow velocity F can be expressed by equation (3) from the relation of equations (1) and (2).

[0008]

## EQU1 ## (V + F cos θ) T1d = L (1)

[0009]

(2) (VF cos θ) T1u = L (2)

[0010]

(Equation 3) In the prior art, as shown in FIG. 5, the flow velocity F expressed by the equation (3) is the propagation time T1 of the ultrasonic signal 1a propagating in the measuring tube 13, but is measured and measured. The propagation time T3 is used for the calculation. The propagation time T3 includes the circuit delay time (τ1 + τ2) of the transmission / reception circuit unit and the ultrasonic sensors 1A and 1A.
There is a delay time (Ts + Tr) due to the delay time in the acoustic matching layer of B and the thickness of the measuring tube 13, and therefore, the flow velocity (flow rate)
An error occurs in the measurement calculation of.

For this reason, in the prior art, for example, (1) flow velocity compensation data is stored in advance by an actual flow calibration test at the time of shipment, and flow velocity compensation calculation processing is performed using this data.

(2) The circuit delay time (τ1 + τ2) or the like is measured in advance by some means such as a manufacturer's in-house test, and this data is stored and corrected to correct the propagation time T3 of the ultrasonic signal 1a. A flow velocity calculation process is performed.

[0013]

As described above, in the flow velocity calculation processing method of the ultrasonic flow meter according to the prior art, (1) the method using the actual flow calibration test at the time of shipment requires the actual flow calibration test, Depending on the flow rate to be measured, a large-scale test facility is required, and a real-time calibration test is required for a shipping test for each individual device. In addition, (2) the method of measuring the circuit delay time in advance in an in-house test, etc., and correcting it with this data to calculate the flow velocity responds to changes in circuit delay time due to changes in circuit characteristics over time and the influence of ambient temperature, etc. Can not do.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to solve the above-mentioned problems and to provide at least ultrasonic signal bypass means,
By providing circuit delay time measurement means, correcting with this data and performing flow velocity calculation processing, it is released from the actual flow calibration test for each individual device, and it can respond to changes over time of circuit characteristics and changes due to the influence of ambient temperature etc. An object of the present invention is to provide an ultrasonic flowmeter.

[0015]

According to the present invention, there is provided an ultrasonic flowmeter which comprises a transmitter and a receiver which are arranged along or inclining with respect to a flow direction of a fluid. An ultrasonic sensor consisting of an ultrasonic transducer and an acoustic matching layer arranged facing each other and one of the ultrasonic sensors are excited, and an ultrasonic signal is switched from the upstream side or the downstream side to the fluid flow and transmitted. The transmitting means and the other ultrasonic sensor detect the ultrasonic signal propagating in the fluid, the receiving section performs reception processing, detects the propagation time of the ultrasonic signal propagating in the fluid, and the downstream or upstream direction A time measuring means for measuring the propagation time of the ultrasonic signal to the, and a flow rate calculating means for calculating the flow velocity or the flow rate of the fluid from these propagation times, in the ultrasonic flowmeter comprising, the transmitting ultrasonic sensor, With the receiving side ultrasonic sensor It is assumed that a bypass unit is provided for transmitting and receiving an electric signal from the transmitting unit to the receiving unit of the time measuring unit, bypassing the interval.

The bypass means includes an attenuator and a switch for dividing the pulse signal for exciting the transmitting ultrasonic sensor by the transmission means, and measures the pulse signal attenuated by the attenuator via the bypass switch. It can be connected to the receiving part of the means.

With this configuration, the bypass unit is switched to the bypass state, the bypass between the transmission-side ultrasonic sensor and the reception-side ultrasonic sensor is bypassed, the excitation pulse signal from the transmission unit is divided, and the reception unit of the time measuring unit is divided. By connecting to, the time from the timing signal emitted at a fixed interval of the transmission means to the detection of the pulse from this timing signal at the reception unit of the time measurement means is measured, and the circuit delay time of the transmission / reception circuit unit is measured. can do.

Further, the bypass means may connect a sine wave signal having the same frequency as the main frequency of the ultrasonic sensor as a test signal to the receiving section of the time measuring means instead of the pulse signal for exciting the transmitting ultrasonic sensor. Can be. With such a configuration, by changing the frequency of the test signal, the delay characteristics of the transmission / reception circuit unit can be considered including the frequency characteristics.

Also, the bypass means connects an electric equivalent circuit equivalent to a vibration circuit by a mechanical-electrical system included in the transmission-side ultrasonic sensor, an electric equivalent circuit of the reception-side ultrasonic sensor, and a circuit between the two equivalent circuits. And a switch for opening and closing.

With this configuration, measurement can be equivalently performed including the delay time characteristics of the transmitting and receiving ultrasonic transducers. As a result, the delay time in the acoustic matching layer of the ultrasonic sensor and the delay time due to the thickness of the measurement tube are obtained in advance, so that the accurate flow velocity correction calculation processing can be performed.

Also, the ultrasonic flowmeter switches the ultrasonic flowmeter from the flow measurement state to the bypass state by the bypass means at the time of periodic inspection or other necessity, and the delay time in the downstream direction and the upstream direction in the bypass state. It is assumed that the delay time is measured, the data is stored and held, and the correction operation is performed based on the data in the flow rate measurement state. By such a calibration, it is possible to switch to the bypass state at any time, measure the delay time, and perform the flow rate correction calculation processing.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of the configuration of an ultrasonic flowmeter according to one embodiment of the present invention and the propagation time delay, and FIG. 2 is the configuration of an ultrasonic flowmeter according to another embodiment and the description of the propagation time delay. FIG. 3 is an equivalent circuit diagram of the ultrasonic transducer, and FIG. 4 is a layout diagram of a general ultrasonic sensor. The same members corresponding to FIG. 5 are denoted by the same reference numerals.

The ultrasonic flowmeter according to the present invention is configured to control the ultrasonic sensors 1A and 1B comprising an ultrasonic transducer 11 and an acoustic matching layer 12 along the flow direction of the fluid 14 or the measurement shown in FIG. The transmitting side and the receiving side are arranged so as to be inclined at an angle θ with respect to the flow direction of the fluid 14 in the tube 13 and separated from the inside of the measuring tube 13 by a distance L to face each other.

In FIG. 1, one ultrasonic sensor, for example, an ultrasonic sensor 1A (1B) is excited, and an ultrasonic signal 1a is transmitted from the upstream side (downstream side) to the flow of the fluid 14. In the illustrated example, the transmitting unit 2 represented by the transmitting unit 21 and the ultrasonic signal propagating in the fluid 14 by the other ultrasonic sensor 1B (1A)
In the example shown in FIG. 1, the receiving unit 31a detects the transmission time T3 (T3d, (T3u)) of the ultrasonic signal 1a in the downstream direction (upstream direction).
/ 32 and a time measuring unit 33, and a flow rate calculating means 4 including a calculating device 41 such as a microcomputer for calculating the flow rate F or the flow rate of the fluid 14 from the propagation times T3 (T3d, T3u). A bypass for transmitting and receiving an electric signal from the transmitting means 2 to the receiving section 31 of the time measuring means 3 by bypassing between the transmitting ultrasonic sensor 1A (1B) and the receiving ultrasonic sensor 1B (1A). In the example shown in the figure, the bypass means 5 includes an attenuator 53 for dividing the pulse signal 2b by which the transmitting means 2 excites the transmitting ultrasonic sensor 1A (1B), and a switch 51.
And the pulse signal attenuated by the attenuator 53 can be connected to the receiving section of the time measuring means via the switch 51.

With this configuration, the bypass unit 5 is switched to the bypass state, and signals are transmitted and received by bypassing the transmission-side ultrasonic sensor 1A (1B) and the reception-side ultrasonic sensor 1B (1A). By dividing the excitation pulse signal 2b from the transmitting means 2 and connecting the signal to the receiving section 31 of the time measuring means 3, the timing signal 2a emitted from the transmitting means 2 at a constant interval can be used by the time measuring means 3. By measuring the time until the detection of the pulse from the timing signal 2a, the circuit delay time of a part of the transmission / reception circuit units 21, 31, 32, and 33 can be measured.

[0026]

(Embodiment 1) In the configuration described in the first embodiment, first, a case will be described in which the switch 51 of the bypass means 5 is opened and the flow velocity F (flow rate) is measured by the ultrasonic signal 1a. . In FIG. 1, a transmitting means 2 transmits a pulse signal at a time t1 at a predetermined constant interval.
2a, and the transmitting unit 21 generates an excitation pulse 2b to the ultrasonic sensor 1.
Is generated, and the upstream sensor 1A selected by a switch SW1 not shown is excited here. The upstream sensor 1A excited by the excitation pulse 2b is an ultrasonic signal having a natural frequency determined by the electro-mechanical system of the ultrasonic sensor 1 and having several cycles to several tens of cycles as illustrated in the lower part of FIG. 1a occurs at time t2.

This ultrasonic signal 1a is transmitted to the fluid 14 in the measuring tube 13
, Is received by the downstream sensor 1B, and is converted into an electric signal 3a. The received electric signal 3a is amplified by the amplifier of the receiving unit 31 via a switch SW2 (not shown), and passes through the band-pass filter 32 through the main frequency component of the natural frequency generated by the ultrasonic sensor 1. And removes electrical and acoustic noise components included in the received signal 3a. The output 3b of the band-pass filter 32 from which the noise component has been removed is detected by the time measurement unit 33, and the time T3 from time t1 to time t3 is measured by, for example, a counter, and the reception signal 3c is output.

There are mainly two methods for detecting the propagation time of the ultrasonic signal 1a from the output 3b of the band-pass filter 32 in the time measuring section 33 as follows. (1) The predetermined reference value h is compared with the output 3b of the band-pass filter 32 using the level comparison method illustrated in the lower part of FIG. 1, and the first signal waveform 3b exceeding the reference value h Time from time t1 to time t3 as time t3
T3 is measured by a counter, for example, and an output 3c of the propagation time T3 is output.

(2) Although not shown in the figure, for example, a zero-crossing method is used in which the influence of noise is relatively small, and the output 3b of the band-pass filter 32 is compared with a comparator to detect a zero-crossing point. On the other hand, the ultrasonic receiving signal amplified by the amplifier of the receiving unit 31 is set to a predetermined reference value.
a predetermined waveform position of the vibration waveform that oscillates at the natural frequency of the ultrasonic signal 1a by comparing the level with (h) (an order)
At the time t3
For example, a time T3 from time t1 to time t3 is measured by a counter, for example, and an output 3c of the propagation time T3 is output. This (2)
In the method of (1), when the received signal 3a of the ultrasonic signal 1a has a pulsation of the amplitude, and the level comparison is difficult in the above (1), or the level comparison can be performed, but even if the propagation time is the same, the signal waveform There is an advantage that the fluctuation of the time t3 due to the compared level of 3b can be eliminated.

In any case, the transmission time T3 detected by the time measuring unit 33 is determined by the transmission
The time t1 (timing signal 2a) at which 1A is excited and the time t3 detected by the time measuring unit 33 by the method (1) or (2)
And the propagation time T3 (T3d) of the ultrasonic signal 1a in the downstream direction from
Can be calculated.

Next, to measure the propagation time T3 of the ultrasonic signal 1a, the switches SW1 and SW2 are switched by the next timing signal 2a to propagate the ultrasonic signal 1a from the downstream sensor 1B to the upstream sensor 1A. Then, a propagation time T3 (T3u) when the ultrasonic signal 1a is propagated in the upstream direction is calculated. By alternately switching these switches SW1 and SW2, the propagation time T3d of the ultrasonic signal 1a in the downstream direction and the propagation time T3u of the ultrasonic signal 1a in the upstream direction can be measured. T3 (T3d, T3u) is subjected to arithmetic processing by an arithmetic unit 41 composed of a microcomputer or the like, and the flow rate F of the fluid 14 is calculated.
Alternatively, the flow rate can be determined.

The propagation time T3 detected by the time measuring unit 33
From time t1 (timing signal 2a) at which the transmitting means 2 excites the ultrasonic sensor 1A to time t3 detected by the time measuring unit 33
This is not the propagation time T1 for propagating in the measurement tube 13 by any of the methods (1) and (2). Therefore, the accurate flow velocity F or flow rate is determined by the circuit delay time (τ1 + τ2) of the transmission / reception circuit section, the delay time in the acoustic matching layer of the ultrasonic sensors 1A and 1B, and the delay time due to the thickness of the measuring tube 13.
(Ts + Tr) can be obtained by Equation (4).

[0033]

(Equation 4) However, τd, τu = τ1 + Ts + Tr + τ2 Next, a case where the bypass unit 5 shown in FIG. 1 is switched to the bypass state will be described. Transmitting ultrasonic sensor 1A (1
When the path between B) and the receiving-side ultrasonic sensor 1B (1A) is in the bypass state, the excitation pulse signal 2b from the transmitting unit 2 is divided and connected to the receiving unit 31 of the time measuring unit 3 to transmit. The time (T3-T2 = τ1 + τ2-τ3) from the time t1 of the timing signal 2a emitted at regular intervals of the means 2 to the time t3 at which the ultrasonic signal 1a is detected by the time measuring means 3 The circuit delay time (τ1 + τ2-
τ3) can be measured.

Here, the time τ3 will be described. Time t2
The transmission-side ultrasonic sensor 1A (1B) oscillates, the ultrasonic signal 1a propagates through the fluid 14, is received by the transmission-side ultrasonic sensor 1B (1A), and the time measurement unit 33 receives the ultrasonic signal 1a. The time t3 at which this is detected is shifted by a time τ3 as compared with the time when the transmission-side ultrasonic sensor 1A (1B) starts oscillating. On the other hand, in the measurement of the circuit delay time τ of the transmission / reception circuit unit according to the method of the first embodiment, the time interval illustrated in T2
Therefore, the measured circuit delay time τ = T3−T2, but the time measurement unit 33 is bypassed and input in the pulse bypass method of the first embodiment. Since the pulse has exceeded the level h, it is detected immediately without being shifted by the time .tau.3.

Therefore, in the correction calculation according to the method of the first embodiment, the delay time (τd1, τd1) measured when the ultrasonic signal is transmitted in the upstream or downstream direction is calculated by the calculation expression (4).
τu1) is a value (Ts + Tr + τ3) obtained by correcting the delay time in the acoustic matching layers of the ultrasonic sensors 1A and 1B, the delay time (Ts + Tr) due to the thickness of the measuring tube 13, and the detection deviation τ3 of the time measuring unit 33. ) Must be corrected. That is, τd and τu in equation (4) are (5),
(6) It is necessary to replace the expression with the calculation.

[0036]

Τd = τd1 + (Ts + Tr + τ3) (5)

[0037]

Τu = τu1 + (Ts + Tr + τ3) (6) Here, the delay time of the acoustic matching layer and the delay time (Ts + Tr) due to the thickness of the measuring tube 13 and the time measuring unit 33 detection shift time τ3
Can be corrected using design values or manufacturer test data values. (Embodiment 2) In addition to the pulse signal 2b that excites the transmission-side ultrasonic sensor 1A (1B) from the transmission unit 21 of the transmission unit 2 to the bypass unit 5, the main unit of the ultrasonic sensor 1A (1B) is used. A sine wave signal having the same frequency as the frequency (usually operating at about 100 kHz to 200 kHz) can be tested as a test signal.
By changing the frequency of the test signal in this way, the phase characteristics of the transmission / reception circuit can be checked. (Embodiment 3) Also, in FIG.
The electrical equivalent circuit 52 of the LCR shown in FIG. 3 which is equivalent to the vibration circuit by the mechanical-electrical system of the transmitting ultrasonic sensor 1A (1B), and the electric equivalent circuit of the receiving ultrasonic sensor 1B (1A)
52, and a switch that opens and closes between the two equivalent circuits 52.

With this configuration, measurement can be equivalently performed including the delay time characteristics of the transmitting and receiving ultrasonic transducers 11. As a result, by determining in advance the delay time in the acoustic matching layer 12 of the ultrasonic sensor 1A (1B) and the delay time due to the thickness of the measurement tube using design data or the like, accurate flow velocity correction calculation processing can be performed. . In particular, in the method of the third embodiment, the time measuring unit 33 uses the level comparison method of (1) or
In any of the zero-cross methods of (2), the delay time (τ) measured when transmitting in the downstream or upstream direction
d2, τu2) is the detection deviation τ of the time measurement unit 33 in FIG.
3 can be measured as the delay time of the ultrasonic signal 1a. Therefore, in the correction calculation by the method of the third embodiment, the delay time (τd2, τd2,
τu2) may be corrected by a value obtained by correcting the delay time in the acoustic matching layer of the ultrasonic sensors 1A and 1B and the delay time (Ts '+ Tr') due to the thickness of the measuring tube 13. That is, τd and τu in equation (4) are
The operation may be performed by replacing the expressions (7) and (8).

[0039]

Τd = τd2 + (Ts '+ Tr') (7)

[0040]

Τu = τu2 + (Ts ′ + Tr ′) (8) where the delay time of the acoustic matching layer and the delay time (Ts ′ + Tr ′) due to the thickness of the measuring tube 13 are Each of them can be corrected using the design value or the manufacturer test data value. (Embodiment 4) Also, at the time of periodic inspection or other necessity, the ultrasonic flowmeter is switched from the flow measurement state to the bypass state by the bypass means 5, and the downstream delay time (τd, τd1, τd2) in the bypass state is obtained. ) And the delay time in the upstream direction (τu, τu1, τu2) are measured, the data is stored and held, and the correction operation can be performed based on the data in the flow rate measurement state.

By such calibration, the state is switched to the bypass state at any time, and the delay time (τd, τd1, τd2), (τu, τu1, τ
By measuring u2), the flow rate F or the flow rate correction calculation processing can be performed more accurately.

[0042]

As described above, by using the ultrasonic flowmeter according to the present invention, by providing the ultrasonic signal bypass means, at least the circuit delay time measuring means is provided, and the circuit delay time measuring means is provided. By storing and holding the measurement data by the above, the calculation process of the flow velocity or the flow rate is corrected and executed by this measurement data,
It is possible to provide an ultrasonic flowmeter that can release a real-flow calibration test for each individual device and can cope with a change over time in circuit characteristics or a change due to the influence of an ambient temperature or the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration of an ultrasonic flowmeter according to an embodiment of the present invention and a propagation time delay.

FIG. 2 is an explanatory diagram of a configuration of an ultrasonic flowmeter according to another embodiment and a propagation time delay.

FIG. 3 is an equivalent circuit diagram of an ultrasonic transducer.

FIG. 4 is a layout diagram of a general ultrasonic sensor.

FIG. 5 is an explanatory diagram of a configuration of a conventional ultrasonic flowmeter and a propagation time delay.

[Explanation of symbols]

 11 Ultrasonic transducer 12 Acoustic matching layer 13 Measurement tube 14 Fluid 1A, 1B Ultrasonic sensor 1a Ultrasonic signal 2 Transmitting means 21 Transmitting unit 2a Timing signal 2b Excitation pulse 3 Time measuring means 31 Receiving unit 32 Bandpass filter 33 Time measuring Part 3a Electric signal 3b, 3c, 4a Output 4 Flow rate calculating means 41 Computing device 5 Bypass means 51 Switch L Distance F Flow rate h Level T1, T2, T3 Propagation time Ts, Tr Delay time t1, t2, t3 Time τ1, τ2, τ3 delay time τ1d, τ2d, τ3d Downstream delay time τ1u, τ2u, τ3u Upstream delay time

Claims (5)

[Claims] 1. An ultrasonic sensor comprising an ultrasonic vibrator and an acoustic matching layer which are provided along a flow direction of a fluid or inclined with respect to the flow direction and have a transmitting side and a receiving side opposed to each other. And a transmitting means for exciting one ultrasonic sensor and switching and transmitting an ultrasonic signal from the upstream side or the downstream side with respect to the flow of the fluid, and transmitting the ultrasonic signal propagating in the fluid with the other ultrasonic sensor. A time measuring means for detecting the propagation time of the ultrasonic signal propagating in the fluid, detecting the propagation time of the ultrasonic signal propagating in the fluid, and measuring the propagation time of the ultrasonic signal in the downstream or upstream direction; and A flow rate calculating means for calculating a flow rate or a flow rate of a fluid from time, wherein a time measuring means is transmitted from the transmitting means by bypassing between the transmitting ultrasonic sensor and the receiving ultrasonic sensor. The receiving part of electricity Ultrasonic flowmeter comprising bypass means, characterized by exchanging items. 2. The ultrasonic flowmeter according to claim 1, wherein the bypass means includes an attenuator for dividing the pulse signal for exciting the transmitting ultrasonic sensor by the transmitting means, and a switch. An ultrasonic flowmeter, wherein the pulse signal attenuated by the above is connected to a receiving section of a time measuring means via a bypass switch. 3. The ultrasonic flowmeter according to claim 1, wherein the bypass unit tests a sine wave signal having the same frequency as the main frequency of the ultrasonic sensor instead of the pulse signal for exciting the transmitting ultrasonic sensor. An ultrasonic flowmeter, which is connected as a signal to a receiving section of a time measuring means. 4. An ultrasonic flowmeter according to claim 1, wherein said bypass means comprises: an electrical equivalent circuit equivalent to a vibration circuit based on a mechanical-electrical system of said transmitting ultrasonic sensor; An ultrasonic flowmeter comprising: the electrical equivalent circuit; and a switch that opens and closes between the two equivalent circuits. 5. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is changed from a flow measurement state to a bypass state by a bypass means at a time of periodic inspection or other necessary time. Switching, measuring the delay time in the downstream direction and the delay time in the upstream direction in the bypass state, storing and holding this data, and performing the correction arithmetic processing based on the data in the flow rate measurement state. Ultrasonic flow meter.