JP2006017568A - Ultrasonic flowmeter and receiving circuit - Google Patents

Ultrasonic flowmeter and receiving circuit Download PDF

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JP2006017568A
JP2006017568A JP2004195177A JP2004195177A JP2006017568A JP 2006017568 A JP2006017568 A JP 2006017568A JP 2004195177 A JP2004195177 A JP 2004195177A JP 2004195177 A JP2004195177 A JP 2004195177A JP 2006017568 A JP2006017568 A JP 2006017568A
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ultrasonic
reception
pseudo
transmission
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Shinji Hirano
真司 平野
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Ricoh Elemex Corp
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/66—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by measuring frequency, phase shift or propagation time of electromagnetic or other waves, e.g. using ultrasonic flowmeters
    • G01F1/667—Arrangements of transducers for ultrasonic flowmeters; Circuits for operating ultrasonic flowmeters
    • G01F1/668—Compensating or correcting for variations in velocity of sound
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/022—Compensating or correcting for variations in pressure, density or temperature using electrical means
    • G01F15/024—Compensating or correcting for variations in pressure, density or temperature using electrical means involving digital counting

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Measuring Volume Flow (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To cancel an electric noise or an impulsive noise generated by transmitting an ultrasonic wave, when detecting the ultrasonic wave transmitted into a passage. <P>SOLUTION: A pseudo ultrasonic element 7 not receiving directly the ultrasonic wave is provided, and a differential output between an ultrasonic conversion signal VIN acquired by receiving the ultrasonic wave transmitted into the passage 3 by an ultrasonic transmitting/receiving element 2a or 2b installed on the upstream side or the downstream side in the flow direction and a pseudo ultrasonic conversion signal VP from the pseudo ultrasonic element 7 is used as an ultrasonic reception signal VOUT. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、超音波流量計および受信回路に関し、詳しくは超音波を利用して流体の流速や流量を計測する超音波流量計およびその受信回路に関する。具体的には、ガスメータ，水道メータ，ガス流量計等の分野で、流体の流量の管理および制御に使用される超音波流量計およびその受信回路に関する。 The present invention relates to an ultrasonic flowmeter and a receiving circuit, and more particularly to an ultrasonic flowmeter that measures the flow velocity and flow rate of a fluid using ultrasonic waves and a receiving circuit thereof. Specifically, the present invention relates to an ultrasonic flow meter used for management and control of a fluid flow rate in a field such as a gas meter, a water meter, and a gas flow meter, and a receiving circuit thereof.

従来、都市ガス，ＬＰＧ，水などの流体の流量を計測する流量計として、超音波を利用して流速および流量を計測する超音波流量計が知られている。その際の計測原理として、一般には「伝搬時間差法」が用いられる。これは、流路の流体流れ方向上手側および下手側に一対の超音波送受信素子を設け、超音波の送受信を交互に切り替えて、流れ方向上手側の超音波送受信素子（送信側振動子）から流れ方向下手側の超音波送受信素子（受信側振動子）に到達するまでの時間（順方向伝搬時間）と、流れ方向下手側の超音波送受信素子（送信側振動子）から流れ方向上手側の超音波送受信素子（受信側振動子）に到達するまでの時間（逆方向伝搬時間）とを計測して、両伝搬時間の差から流路を流れる流体の平均流速および平均流速に流路断面積を乗算することで流量を求める方法である。 2. Description of the Related Art Conventionally, as a flow meter that measures the flow rate of a fluid such as city gas, LPG, or water, an ultrasonic flow meter that measures flow velocity and flow rate using ultrasonic waves is known. As a measurement principle at that time, the “propagation time difference method” is generally used. This is because a pair of ultrasonic transmission / reception elements are provided on the upper and lower sides of the fluid flow direction of the flow path, and the ultrasonic transmission / reception elements (transmission-side transducers) on the upper side in the flow direction are switched alternately. The time required to reach the ultrasonic transmission / reception element (reception-side transducer) on the lower side in the flow direction (forward propagation time) and the ultrasonic transmission / reception element (transmission-side transducer) on the lower side in the flow direction. Measure the time (reverse propagation time) to reach the ultrasonic transmitter / receiver element (reception-side transducer) and calculate the average flow velocity and average flow velocity of the fluid flowing through the flow path from the difference between the two propagation times. The flow rate is obtained by multiplying

図８は、従来の超音波流量計で用いられている受信回路の一例を示す回路図である。この受信回路は、オペアンプＵ１を主体とする第１の反転増幅器と、オペアンプＵ２を主体とする第２の反転増幅器とが直列に接続されて構成されている。オペアンプＵ１の反転入力端子は、抵抗Ｒ１およびコンデンサＣ１を通じて一端が接地された超音波送受信素子ＵＳＭ１の他端に接続されているとともに、抵抗Ｒ２を通じてオペアンプＵ１の出力端子ＯＵＴに接続されている。超音波送受信素子ＵＳＭ１には、抵抗Ｒ３が並列に接続されている。また、オペアンプＵ１の非反転入力端子は、抵抗Ｒ４を通じて接地されている。オペアンプＵ１の出力端子ＯＵＴは、抵抗Ｒ５を通じてオペアンプＵ２の反転入力端子に接続されており、オペアンプＵ２の反転入力端子は抵抗Ｒ６を通じてオペアンプＵ２の出力端子ＯＵＴに接続されている。オペアンプＵ２の非反転入力端子は、抵抗Ｒ７を通じて接地されている。オペアンプＵ２の出力端子ＯＵＴからは、超音波受信信号ＶＯＵＴが出力される。なお、図８中、符号ＶＤＤは電源電圧、ＶＳＳはマイナス電源電圧を示す。 FIG. 8 is a circuit diagram showing an example of a receiving circuit used in a conventional ultrasonic flowmeter. This receiving circuit is configured by connecting a first inverting amplifier mainly composed of an operational amplifier U1 and a second inverting amplifier mainly composed of an operational amplifier U2. The inverting input terminal of the operational amplifier U1 is connected to the other end of the ultrasonic transmitting / receiving element USM1 whose one end is grounded through the resistor R1 and the capacitor C1, and is connected to the output terminal OUT of the operational amplifier U1 through the resistor R2. A resistor R3 is connected in parallel to the ultrasonic transmitting / receiving element USM1. The non-inverting input terminal of the operational amplifier U1 is grounded through the resistor R4. The output terminal OUT of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U2 through the resistor R5, and the inverting input terminal of the operational amplifier U2 is connected to the output terminal OUT of the operational amplifier U2 through the resistor R6. The non-inverting input terminal of the operational amplifier U2 is grounded through the resistor R7. The ultrasonic reception signal VOUT is output from the output terminal OUT of the operational amplifier U2. In FIG. 8, reference sign VDD indicates a power supply voltage, and VSS indicates a negative power supply voltage.

このような従来の受信回路では、超音波送受信素子ＵＳＭ１で超音波が受信されると、超音波は機械−電気変換されて超音波変換信号ＶＩＮとしてコンデンサＣ１および抵抗Ｒ１を通じてオペアンプＵ１の非反転入力端子に印加される。オペアンプＵ１は、抵抗Ｒ１，Ｒ２で決まる増幅率で超音波変換信号ＶＩＮを増幅し、増幅信号をさらにオペアンプＵ２が抵抗Ｒ５，Ｒ６で決まる増幅率で増幅して、超音波受信信号ＶＯＵＴとして出力する。 In such a conventional receiving circuit, when the ultrasonic wave is received by the ultrasonic wave transmitting / receiving element USM1, the ultrasonic wave is mechanical-electrically converted to an ultrasonic conversion signal VIN as a non-inverting input of the operational amplifier U1 through the capacitor C1 and the resistor R1. Applied to the terminal. The operational amplifier U1 amplifies the ultrasonic conversion signal VIN at an amplification factor determined by the resistors R1 and R2, and further amplifies the amplified signal at an amplification factor determined by the resistors R5 and R6 and outputs the amplified signal as an ultrasonic reception signal VOUT. .

ところで、従来の超音波流量計では、電池駆動の超音波流量計を可能にするために、消費電流の大きい増幅・比較回路からなる受信回路の電源を、超音波受信信号を検出する直前にオンし、超音波受信信号を検出したならばオフするようにしていた（例えば、特許文献１参照）。 By the way, in the conventional ultrasonic flowmeter, in order to enable a battery-driven ultrasonic flowmeter, the power supply of the receiving circuit consisting of an amplification / comparison circuit with large current consumption is turned on immediately before detecting the ultrasonic reception signal. If an ultrasonic reception signal is detected, the signal is turned off (see, for example, Patent Document 1).

また、従来の他の超音波流量計では、電池消費を抑止するために、超音波送受信素子を駆動後、受信回路の電源をオンし、超音波受信信号が検出できても、できなくても、一定時間後にオフするようにしていた（例えば、特許文献２参照）。
特許第０２８２８６１５号公報 特開２００２−１４８０８５６号公報 Also, in other conventional ultrasonic flowmeters, in order to suppress battery consumption, after the ultrasonic transmission / reception element is driven, the power of the receiving circuit is turned on so that the ultrasonic reception signal can be detected or not. The power is turned off after a certain time (see, for example, Patent Document 2).
Japanese Patent No. 0288615 JP 2002-1480856 A

ところで、従来の超音波流量計では、図８に示すような受信回路を使用した場合、図９に示すように、超音波受信信号ＶＯＵＴとして、受信側の超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮの他に、送信側の超音波送受信素子（図示せず）の駆動直後に発生する電気的なノイズおよびインパルス的なノイズ（以下、駆動直後ノイズと総称する）が検出されるという問題点があった。 By the way, in the conventional ultrasonic flowmeter, when a receiving circuit as shown in FIG. 8 is used, as shown in FIG. 9, ultrasonic conversion from the ultrasonic transmitting / receiving element USM1 on the receiving side is performed as an ultrasonic receiving signal VOUT. In addition to the signal VIN, electrical noise and impulse noise (hereinafter collectively referred to as noise immediately after driving) generated immediately after driving a transmitting-side ultrasonic transmitting / receiving element (not shown) are detected. was there.

受信側の超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮに重畳される駆動直後ノイズのノイズ源は、送信回路を通して送信側の超音波送受信素子に流れ込む電流であり、このような負荷がかかることにより送信回路の電源電圧が変動し、その影響が受信回路の電源にも回り込んでいた。超音波流量計では、伝搬する超音波が距離や流体により減衰するので、受信回路の増幅率は６０ｄＢ以上確保する必要があり、受信回路の増幅率が大きいために、その電源電圧の変動が超音波受信信号ＶＯＵＴにダイレクトに表れていた。 The noise source of the noise immediately after driving that is superimposed on the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element USM1 on the reception side is a current flowing into the ultrasonic transmission / reception element on the transmission side through the transmission circuit, and this load is applied. As a result, the power supply voltage of the transmission circuit fluctuated, and the influence of the fluctuation also spread to the power supply of the reception circuit. In the ultrasonic flowmeter, since the propagating ultrasonic wave is attenuated by the distance and the fluid, it is necessary to secure an amplification factor of the receiving circuit of 60 dB or more. Since the amplification factor of the receiving circuit is large, the fluctuation of the power supply voltage is excessive. It appeared directly in the sound wave reception signal VOUT.

ここで、送信側の超音波送受信素子を駆動して、流路内に超音波が送信されてから、流路内に送信された超音波を受信側の超音波送受信素子ＵＳＭ１で受信するまでの状況をさらに詳しく説明する。 Here, after the ultrasonic transmission / reception element on the transmission side is driven and the ultrasonic wave is transmitted in the flow path, the ultrasonic wave transmitted in the flow path is received by the ultrasonic transmission / reception element USM1 on the reception side. Explain the situation in more detail.

送信側の超音波送受信素子に駆動パルスが印加されると、それに応じて送信側の超音波送受信素子は振動を開始し、流路内に超音波が送信される。この時、超音波の送信により、送信側の超音波送受信素子に電流が流れるが、この電流値は、非動作時より大きな電流値となる。この超音波放射時の消費電流により、一時的に、回路全体の電源電圧が降下すると、送信回路ばかりでなく受信回路の電源電圧も降下する。受信回路の電圧降下の影響により、受信回路は超音波を受信していないにも拘わらず、あたかも超音波を受信したかような駆動直後ノイズを出力する。 When a drive pulse is applied to the transmission-side ultrasonic transmission / reception element, the transmission-side ultrasonic transmission / reception element starts to vibrate accordingly, and ultrasonic waves are transmitted into the flow path. At this time, due to the transmission of ultrasonic waves, a current flows through the ultrasonic transmission / reception element on the transmission side, but this current value is larger than that during non-operation. When the power supply voltage of the entire circuit temporarily drops due to the current consumption during the ultrasonic radiation, not only the transmission circuit but also the power supply voltage of the reception circuit drops. Due to the voltage drop of the receiving circuit, the receiving circuit outputs noise immediately after driving as if the ultrasonic wave was received, even though the ultrasonic wave was not received.

流路内に送信された超音波が受信側の超音波送受信素子ＵＳＭ１で受信されて変換された超音波変換信号ＶＩＮと、送信側の超音波送受信素子を駆動して超音波を送信したことによって発生した駆動直後ノイズとを比較して、駆動直後ノイズが十分に小さくなって、十二分に減衰すれば、流量計測時に特に問題はない。しかし、例えば、超音波流量計において、流量１Ｌ／ｈを計測するような高精度な計測が要求される場合、超音波変換信号ＶＩＮと駆動直後ノイズとのＳ／Ｎ比を十分に確保して、駆動直後ノイズに対して影響を受けない受信回路にすることが望ましい。 The ultrasonic wave transmitted into the flow path is received and converted by the ultrasonic transmitting / receiving element USM1 on the receiving side, and the ultrasonic wave is transmitted by driving the ultrasonic transmitting / receiving element on the transmitting side. If the noise immediately after driving is sufficiently reduced and sufficiently attenuated by comparing with the generated noise immediately after driving, there is no particular problem when measuring the flow rate. However, for example, in an ultrasonic flowmeter, when high-precision measurement is required to measure a flow rate of 1 L / h, a sufficient S / N ratio between the ultrasonic conversion signal VIN and noise immediately after driving is ensured. It is desirable to use a receiving circuit that is not affected by noise immediately after driving.

このような駆動直後ノイズの対策として、従来は、電源に大きな容量のコンデンサを追加して電源電圧の変動を抑制する方法があった。しかし、この方法は、電源電圧の変動を抑制することは可能であるが、そのレベルは、数ｍＶの安定性を確保するものではなく、わずかながら電源電圧が変動するので、受信回路はやはり影響を受けるという問題点があった。 As a countermeasure against such noise immediately after driving, there has conventionally been a method of suppressing fluctuations in power supply voltage by adding a capacitor having a large capacity to the power supply. However, this method can suppress fluctuations in the power supply voltage, but the level does not ensure stability of several mV, and the power supply voltage fluctuates slightly, so that the receiving circuit is still affected. There was a problem of receiving.

また、駆動直後ノイズを受信しないために、超音波が受信されない区間は受信回路の電源をオフにしておくようにマスク時間を設ける方法があった。しかし、この方法は、単に受信時において駆動直後ノイズを誤検出しないようにしているだけであって、駆動直後ノイズをキャンセルしているわけではないという問題点があった。また、この時、発生した駆動直後ノイズは、しばらくの間、あたかも受信側の超音波送受信素子が振動して、その後の残響成分で振動しているかのような出力を示すという問題点があった。 In addition, in order not to receive noise immediately after driving, there is a method of providing a mask time so that the power of the receiving circuit is turned off in a section where no ultrasonic wave is received. However, this method has a problem that noise immediately after driving is not erroneously detected at the time of reception, and noise is not canceled immediately after driving. In addition, at this time, the generated noise immediately after driving has a problem that the ultrasonic transmission / reception element on the receiving side vibrates for a while and the output appears as if it vibrates with the reverberation component thereafter. .

なお、先に挙げた特許文献１および特許文献２に記載された従来の技術においても、超音波が受信されない区間は受信回路の電源をオフにしておくようにしていたが、その目的は、省電力動作のために受信回路の電源をオフしておくようにしているだけであって、本発明の目的である駆動直後ノイズなどをキャンセルする、あるいは低減するという目的とは異なるものである。 In the conventional techniques described in Patent Document 1 and Patent Document 2 described above, the power of the receiving circuit is kept off in the section where the ultrasonic waves are not received. The power supply of the receiving circuit is merely turned off for power operation, which is different from the purpose of canceling or reducing noise immediately after driving, which is the object of the present invention.

本発明の課題は、流路内に送信された超音波を検出する時、超音波を送信することによって発生した駆動直後ノイズ（電気的なノイズやインパルス的なノイズ）をキャンセルできるようにした超音波流量計を提供することにある。 An object of the present invention is to detect noise immediately after driving (electrical noise or impulse noise) generated by transmitting ultrasonic waves when detecting ultrasonic waves transmitted into a flow path. To provide a sonic flow meter.

また、本発明の他の課題は、超音波を送信することによって発生した駆動直後ノイズ（電気的なノイズやインパルス的なノイズ）をキャンセルできるようにした受信回路を提供することにある。 Another object of the present invention is to provide a receiving circuit capable of canceling noise immediately after driving (electrical noise or impulse noise) generated by transmitting ultrasonic waves.

課題を解決するための手段および発明の効果Means for Solving the Problems and Effects of the Invention

請求項１記載の超音波流量計は、流体を通過させる流路内の流体の流れ方向上手側および下手側に取り付けられた一対の超音波送受信素子と、前記一対の超音波送受信素子の一方を駆動して超音波を送信させる送信回路と、超音波を直接受信しない擬似超音波素子と、前記一対の超音波送受信素子の他方で受信した超音波の超音波変換信号と、前記擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力する受信回路とを有する構成である。請求項１記載の超音波流量計によれば、受信側の超音波送受信素子からの超音波変換信号と、擬似的に設けられた擬似超音波素子からの擬似超音波変換信号との差動出力を超音波受信信号とするため、超音波流量計の回路系上に重畳される駆動直後ノイズをキャンセルすることが可能となり、耐ノイズ性が向上し、低ノイズで高精度な流量計測が実現できる。 The ultrasonic flowmeter according to claim 1 includes a pair of ultrasonic transmission / reception elements attached to the upper and lower sides of the flow direction of the fluid in the flow path through which the fluid passes, and one of the pair of ultrasonic transmission / reception elements. A transmission circuit that drives and transmits ultrasonic waves, a pseudo ultrasonic element that does not directly receive ultrasonic waves, an ultrasonic conversion signal of ultrasonic waves received by the other of the pair of ultrasonic transmission / reception elements, and the pseudo ultrasonic element And a reception circuit that outputs a differential output from the pseudo ultrasonic wave conversion signal generated in step 1 as an ultrasonic reception signal. According to the ultrasonic flowmeter of claim 1, the differential output between the ultrasonic conversion signal from the ultrasonic transmission / reception element on the receiving side and the pseudo ultrasonic conversion signal from the pseudo ultrasonic element provided in a pseudo manner. Because it is an ultrasonic reception signal, it is possible to cancel noise immediately after driving superimposed on the circuit system of the ultrasonic flowmeter, improve noise resistance, and realize high-precision flow measurement with low noise. .

請求項２記載の超音波流量計は、流体を通過させる流路内の流体の流れ方向上手側および下手側に取り付けられた一対の超音波送受信素子と、前記一対の超音波送受信素子の一方を送信側、他方を受信側として切り替える順／逆切替手段と、前記送信側の超音波送受信素子を駆動して超音波を送信させる送信回路と、超音波を直接受信しない擬似超音波素子と、前記受信側の超音波送受信素子で受信した超音波の超音波変換信号と、前記擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力する受信回路とを有することを特徴とする。請求項２記載の超音波流量計によれば、順／逆切替手段を設けたことにより、流れ方向上手側および下手側に取り付けられた一対の超音波送受信素子に対して、１つの擬似超音波素子を備えるだけですむようになるので、超音波流量計の構成部品がシンプルになって安価に製造でき、かつ、高精度な流量計測を行なうことができる。 The ultrasonic flowmeter according to claim 2 includes a pair of ultrasonic transmission / reception elements attached to the upper and lower sides of the flow direction of the fluid in the flow path through which the fluid passes, and one of the pair of ultrasonic transmission / reception elements. Forward / reverse switching means for switching the transmitting side as the receiving side, a transmitting circuit for driving the transmitting side ultrasonic transmitting / receiving element to transmit ultrasonic waves, a pseudo ultrasonic element not directly receiving ultrasonic waves, A receiving circuit that outputs a differential output between the ultrasonic conversion signal of the ultrasonic wave received by the ultrasonic transmitting / receiving element on the receiving side and the pseudo ultrasonic wave conversion signal generated by the pseudo ultrasonic element as an ultrasonic wave reception signal; It is characterized by that. According to the ultrasonic flowmeter of claim 2, by providing the forward / reverse switching means, one pseudo ultrasonic wave is applied to a pair of ultrasonic transmission / reception elements attached on the upper and lower sides in the flow direction. Since only an element is required, the components of the ultrasonic flowmeter can be simplified and manufactured at low cost, and highly accurate flow measurement can be performed.

請求項３記載の超音波流量計は、請求項１または請求項２に記載の超音波流量計において、前記擬似超音波素子が、超音波の送信および受信が可能な超音波送受信素子でなることを特徴とする。請求項３記載の超音波流量計によれば、擬似超音波素子が、流路内の超音波を送信および受信可能な超音波送受信素子と同じ特性となるため、超音波送受信素子が持つ電気的特性と一致させる必要がなくなり、送信側の超音波送受信素子が持つ固有の特性によって生じる駆動直後ノイズを簡単にキャンセルすることができる。 The ultrasonic flowmeter according to claim 3 is the ultrasonic flowmeter according to claim 1 or 2, wherein the pseudo ultrasonic element is an ultrasonic transmission / reception element capable of transmitting and receiving ultrasonic waves. It is characterized by. According to the ultrasonic flowmeter of the third aspect, since the pseudo ultrasonic element has the same characteristics as the ultrasonic transmission / reception element capable of transmitting and receiving the ultrasonic wave in the flow path, the electrical characteristics of the ultrasonic transmission / reception element are included. It is not necessary to match the characteristics, and noise immediately after driving caused by unique characteristics of the transmitting-side ultrasonic transmitting / receiving element can be easily canceled.

請求項４記載の超音波流量計は、請求項１または請求項２記載の超音波流量計において、前記擬似超音波素子が、超音波送受信素子などの圧電体以外の受動素子で構成され、かつ前記一対の超音波送受信素子と電気的特性を同一にしたことを特徴とする。請求項４記載の超音波流量計によれば、擬似超音波素子を、一対の超音波送受信素子に対して電気的特性を同一にし、超音波送受信素子などの圧電素子以外の受動素子のみで構成するようにしたので、超音波流量計を安価に製造できるという利点がある。 The ultrasonic flowmeter according to claim 4 is the ultrasonic flowmeter according to claim 1 or 2, wherein the pseudo ultrasonic element is composed of a passive element other than a piezoelectric body such as an ultrasonic transmission / reception element, and The electrical characteristics of the pair of ultrasonic transmitting / receiving elements are the same. According to the ultrasonic flowmeter of claim 4, the pseudo ultrasonic element has the same electrical characteristics as the pair of ultrasonic transmission / reception elements, and includes only passive elements other than piezoelectric elements such as the ultrasonic transmission / reception elements. Thus, there is an advantage that the ultrasonic flowmeter can be manufactured at low cost.

請求項５記載の超音波流量計は、請求項１ないし請求項４のいずれかに記載の超音波流量計において、前記擬似超音波素子が、前記一対の超音波送受信素子と温度特性が同一であることを特徴とする。請求項５記載の超音波流量計によれば、擬似超音波素子の温度特性を一対の超音波送受信素子の温度特性と同一にすることにより、環境温度変化に対する影響もなくなり、高精度な流量計測が可能となる。 The ultrasonic flowmeter according to claim 5 is the ultrasonic flowmeter according to any one of claims 1 to 4, wherein the pseudo ultrasonic element has the same temperature characteristics as the pair of ultrasonic transmission / reception elements. It is characterized by being. According to the ultrasonic flowmeter of claim 5, by making the temperature characteristic of the pseudo ultrasonic element the same as the temperature characteristic of the pair of ultrasonic transmission / reception elements, there is no influence on the environmental temperature change, and highly accurate flow measurement. Is possible.

請求項６記載の超音波流量計は、請求項１ないし請求項５のいずれかに記載の超音波流量計において、前記受信回路が、前記一対の超音波送受信素子の一方からの超音波変換信号を任意の増幅率で増幅する超音波変換信号増幅回路と、前記擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅する擬似超音波変換信号増幅回路とを備え、前記超音波変換信号増幅回路の増幅信号および前記擬似超音波変換信号増幅回路の増幅信号の差動出力を超音波受信信号として出力することを特徴とする。請求項６記載の超音波流量計によれば、超音波変換信号増幅回路が受信側の超音波送受信素子からの超音波変換信号を任意の増幅率で増幅し、擬似超音波変換信号増幅回路が擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅して、超音波変換信号の増幅信号と擬似超音波変換信号の増幅信号との差動出力を超音波受信信号とするので、超音波変換信号増幅回路および擬似超音波変換信号増幅回路がバッファの役割をするために超音波変換信号および擬似超音波変換信号が安定したものとなり、超音波受信信号が駆動直後ノイズに対して影響を受けにくくなるために高精度の流量計測が可能となる。 The ultrasonic flowmeter according to claim 6 is the ultrasonic flowmeter according to any one of claims 1 to 5, wherein the reception circuit receives an ultrasonic conversion signal from one of the pair of ultrasonic transmission / reception elements. An ultrasonic conversion signal amplifying circuit for amplifying the pseudo ultrasonic conversion signal from the pseudo ultrasonic element with an arbitrary amplification factor, and the ultrasonic wave The differential output of the amplified signal of the conversion signal amplification circuit and the amplification signal of the pseudo ultrasonic conversion signal amplification circuit is output as an ultrasonic reception signal. According to the ultrasonic flowmeter of the sixth aspect, the ultrasonic conversion signal amplification circuit amplifies the ultrasonic conversion signal from the ultrasonic transmission / reception element on the receiving side at an arbitrary amplification factor, and the pseudo ultrasonic conversion signal amplification circuit Since the pseudo ultrasonic conversion signal from the pseudo ultrasonic element is amplified at an arbitrary amplification factor, the differential output between the amplified signal of the ultrasonic conversion signal and the amplified signal of the pseudo ultrasonic conversion signal is used as the ultrasonic reception signal. Since the ultrasonic conversion signal amplification circuit and the pseudo ultrasonic conversion signal amplification circuit act as a buffer, the ultrasonic conversion signal and the pseudo ultrasonic conversion signal become stable, and the ultrasonic reception signal is Highly accurate flow rate measurement is possible because it is less affected.

請求項７記載の超音波流量計は、請求項１ないし請求項６のいずれかに記載の超音波流量計において、前記送信回路の電源と前記受信回路の電源とを別々にしたことを特徴とする。請求項７記載の超音波流量計によれば、送信回路の電源と受信回路の電源とを別々にすることにより、受信回路の電源が、超音波送受信素子を駆動することによって送信回路の電源に発生する電源電圧降下などの影響を受けにくくなるため、より高精度な流量計測が可能となる。 The ultrasonic flowmeter according to claim 7 is the ultrasonic flowmeter according to any one of claims 1 to 6, wherein a power source of the transmitting circuit and a power source of the receiving circuit are separately provided. To do. According to the ultrasonic flowmeter of the seventh aspect, by separating the power supply of the transmission circuit and the power supply of the reception circuit, the power supply of the reception circuit becomes the power supply of the transmission circuit by driving the ultrasonic transmission / reception element. Since it is less susceptible to the power supply voltage drop that occurs, more accurate flow rate measurement is possible.

請求項８記載の受信回路は、超音波送受信素子で受信した超音波の超音波変換信号と、超音波を直接受信しない擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力することを特徴とする。請求項８記載の受信回路によれば、超音波送受信素子からの超音波変換信号と擬似超音波素子からの擬似超音波変換信号との差動出力を超音波受信信号とすることにより、超音波変換信号に含まれる駆動直後ノイズと、擬似超音波変換信号に含まれる駆動直後ノイズとがキャンセルされて、超音波受信信号に駆動直後ノイズが出力されなくなる。 The reception circuit according to claim 8 is configured to receive a differential output between an ultrasonic conversion signal of an ultrasonic wave received by an ultrasonic transmission / reception element and a pseudo ultrasonic conversion signal generated by a pseudo ultrasonic element that does not directly receive the ultrasonic wave. It is output as a sound wave reception signal. According to the receiving circuit of the eighth aspect, the differential output between the ultrasonic conversion signal from the ultrasonic transmission / reception element and the pseudo ultrasonic conversion signal from the pseudo ultrasonic element is used as the ultrasonic reception signal. The noise immediately after driving included in the conversion signal and the noise immediately after driving included in the pseudo ultrasonic wave conversion signal are canceled, and the noise immediately after driving is not output to the ultrasonic wave reception signal.

請求項９記載の受信回路は、請求項８に記載の受信回路において、前記超音波送受信素子からの超音波変換信号を任意の増幅率で増幅する超音波変換信号増幅回路と、前記擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅する擬似超音波変換信号増幅回路とを備え、前記超音波変換信号増幅回路の増幅信号および前記擬似超音波変換信号増幅回路の増幅信号の差動出力を超音波受信信号として出力することを特徴とする。請求項９記載の受信回路によれば、超音波変換信号増幅回路が受信側の超音波送受信素子からの超音波変換信号を任意の増幅率で増幅し、擬似超音波変換信号増幅回路が擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅して、超音波変換信号の増幅信号と擬似超音波変換信号の増幅信号との差動出力を超音波受信信号とするので、超音波変換信号増幅回路および擬似超音波変換信号増幅回路がバッファの役割をするために超音波変換信号および擬似超音波変換信号が安定したものとなり、超音波受信信号が駆動直後ノイズに対して影響を受けにくくなるために高精度の流量計測が可能となる。 A receiving circuit according to claim 9 is the receiving circuit according to claim 8, wherein an ultrasonic conversion signal amplification circuit that amplifies an ultrasonic conversion signal from the ultrasonic transmitting / receiving element at an arbitrary amplification factor, and the pseudo ultrasonic wave A pseudo ultrasonic conversion signal amplifying circuit for amplifying the pseudo ultrasonic conversion signal from the element at an arbitrary amplification factor, the amplified signal of the ultrasonic conversion signal amplifying circuit and the amplified signal of the pseudo ultrasonic conversion signal amplifying circuit The differential output is output as an ultrasonic reception signal. According to the receiving circuit of the ninth aspect, the ultrasonic conversion signal amplification circuit amplifies the ultrasonic conversion signal from the ultrasonic transmission / reception element on the receiving side with an arbitrary amplification factor, and the pseudo ultrasonic conversion signal amplification circuit Since the pseudo ultrasonic conversion signal from the ultrasonic element is amplified at an arbitrary amplification factor, the differential output between the amplification signal of the ultrasonic conversion signal and the amplification signal of the pseudo ultrasonic conversion signal is used as the ultrasonic reception signal. Since the ultrasonic wave conversion signal amplification circuit and the pseudo ultrasonic wave conversion signal amplification circuit act as a buffer, the ultrasonic wave conversion signal and the pseudo ultrasonic wave conversion signal become stable, and the ultrasonic wave reception signal affects the noise immediately after driving. Since it becomes difficult to receive, highly accurate flow rate measurement becomes possible.

超音波を直接受信しない擬似超音波素子を擬似的に設け、流路内に送信された超音波を流れ方向上手側または下手側に取り付けられた超音波送受信素子で変換された超音波変換信号と、擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号とすることにより、流路内に送信された超音波を検出する時、超音波を送信することにより発生した駆動直後ノイズ（電気的なノイズやインパルス的なノイズ）をキャンセルした。 A pseudo ultrasonic element that does not directly receive ultrasonic waves is provided in a pseudo manner, and an ultrasonic wave conversion signal converted by an ultrasonic wave transmitting / receiving element attached to the upper side or lower side of the flow direction of the ultrasonic wave transmitted in the flow path and Generated by transmitting the ultrasonic wave when detecting the ultrasonic wave transmitted in the flow path by making the differential output with the pseudo ultrasonic wave conversion signal generated by the pseudo ultrasonic element as an ultrasonic reception signal Canceled noise immediately after driving (electrical noise or impulse noise).

以下、本発明の実施例について図面を参照しながら詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

図１は、本発明の実施例１に係る受信回路を示す回路図である。本実施例１に係る受信回路は、オペアンプＵ１を主体とする差動増幅器１１と、オペアンプＵ２を主体とする反転増幅器１２とが直列に接続されて構成されている。オペアンプＵ１の反転入力端子は、抵抗Ｒ１およびコンデンサＣ１を通じて一端が接地された超音波送受信素子ＵＳＭ１の他端に接続されているとともに、抵抗Ｒ２を通じてオペアンプＵ１の出力端子ＯＵＴに接続されている。超音波送受信素子ＵＳＭ１には、抵抗Ｒ５が並列に接続されている。また、オペアンプＵ１の非反転入力端子は、抵抗Ｒ３およびコンデンサＣ２を通じて一端が接地された擬似超音波素子ＵＳＭＸの他端に接続されているとともに、抵抗Ｒ４を通じて接地されている。擬似超音波素子ＵＳＭＸには、抵抗Ｒ６が並列に接続されている。オペアンプＵ１の出力端子ＯＵＴは、抵抗Ｒ７を通じてオペアンプＵ２の反転入力端子に接続されており、オペアンプＵ２の反転入力端子は抵抗Ｒ８を通じてオペアンプＵ２の出力端子ＯＵＴに接続されている。オペアンプＵ２の非反転入力端子は、抵抗Ｒ９を通じて接地されている。オペアンプＵ２の出力端子ＯＵＴからは、超音波受信信号ＶＯＵＴが出力される。なお、図１中、符号ＶＤＤは電源電圧、ＶＳＳはマイナス電源電圧を示す。 FIG. 1 is a circuit diagram illustrating a receiving circuit according to Embodiment 1 of the present invention. The receiving circuit according to the first embodiment is configured by connecting a differential amplifier 11 mainly composed of an operational amplifier U1 and an inverting amplifier 12 mainly composed of an operational amplifier U2. The inverting input terminal of the operational amplifier U1 is connected to the other end of the ultrasonic transmitting / receiving element USM1 whose one end is grounded through the resistor R1 and the capacitor C1, and is connected to the output terminal OUT of the operational amplifier U1 through the resistor R2. A resistor R5 is connected in parallel to the ultrasonic transmitting / receiving element USM1. The non-inverting input terminal of the operational amplifier U1 is connected to the other end of the pseudo ultrasonic element USMX whose one end is grounded through the resistor R3 and the capacitor C2, and is grounded through the resistor R4. A resistor R6 is connected in parallel to the pseudo ultrasonic element USMX. The output terminal OUT of the operational amplifier U1 is connected to the inverting input terminal of the operational amplifier U2 through the resistor R7, and the inverting input terminal of the operational amplifier U2 is connected to the output terminal OUT of the operational amplifier U2 through the resistor R8. The non-inverting input terminal of the operational amplifier U2 is grounded through the resistor R9. The ultrasonic reception signal VOUT is output from the output terminal OUT of the operational amplifier U2. In FIG. 1, reference sign VDD indicates a power supply voltage, and VSS indicates a negative power supply voltage.

擬似超音波素子ＵＳＭＸは、超音波を直接受信しない素子ではあるが、超音波送受信素子ＵＳＭ１と電気的特性が同一であることが望ましい。このため、擬似超音波素子ＵＳＭＸは、超音波の送信および受信が可能な超音波送受信素子で形成することができる。このようにすれば、擬似超音波素子ＵＳＭＸは、超音波送受信素子ＵＳＭ１とほぼ同じ素子特性を持ち、超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮと擬似超音波素子ＵＳＭＸからの擬似超音波変換信号ＶＰとの差動出力を超音波受信信号ＶＯＵＴとすることにより、超音波送受信素子ＵＳＭ１の特性と擬似超音波素子ＵＳＭＸの特性とが相殺されることになる。このため、超音波送受信素子ＵＳＭ１と擬似超音波素子ＵＳＭＸとの電気的特性，温度特性等を合わせる手間を省くことができる。 The pseudo ultrasonic element USMX is an element that does not directly receive an ultrasonic wave, but desirably has the same electrical characteristics as the ultrasonic transmission / reception element USM1. For this reason, the pseudo ultrasonic element USMX can be formed of an ultrasonic transmission / reception element capable of transmitting and receiving ultrasonic waves. In this way, the pseudo ultrasonic element USMX has substantially the same element characteristics as the ultrasonic transmission / reception element USM1, and the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element USM1 and the pseudo ultrasonic conversion from the pseudo ultrasonic element USMX. By using the differential output with the signal VP as the ultrasonic reception signal VOUT, the characteristic of the ultrasonic transmission / reception element USM1 and the characteristic of the pseudo ultrasonic element USMX are offset. For this reason, it is possible to save the trouble of matching the electrical characteristics, temperature characteristics, and the like of the ultrasonic transmitting / receiving element USM1 and the pseudo ultrasonic element USMX.

また、擬似超音波素子ＵＳＭＸは、図２に示すように、超音波送受信素子などの圧電体以外の受動素子で形成するようにしてもよい。すなわち、擬似超音波素子ＵＳＭＸを、抵抗ＲａとコンデンサＣａ，Ｃｂ，コイルＬａの直列回路との並列回路などの受動素子からなる等化回路により構成し、超音波送受信素子ＵＳＭ１の電気的特性と同一の電気的特性を有するように形成することができる。なお、電気的特性とは、インピーダンス，静電容量などである。このように構成すれば、超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮと擬似超音波素子ＵＳＭＸからの擬似超音波変換信号ＶＰとの差動出力を超音波受信信号ＶＯＵＴとすることにより、擬似超音波素子ＵＳＭＸと超音波送受信素子ＵＳＭ１との静特性や動特性の依存性がキャンセルされることになる。 Further, as shown in FIG. 2, the pseudo ultrasonic element USMX may be formed of a passive element other than a piezoelectric body such as an ultrasonic transmission / reception element. That is, the pseudo ultrasonic element USMX is configured by an equalization circuit including a passive element such as a parallel circuit of a resistor Ra, capacitors Ca, Cb, and a coil La, and has the same electrical characteristics as the ultrasonic transmission / reception element USM1. It can be formed to have the following electrical characteristics. Note that the electrical characteristics include impedance, capacitance, and the like. With this configuration, the differential output between the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element USM1 and the pseudo ultrasonic conversion signal VP from the pseudo ultrasonic element USMX is used as the ultrasonic reception signal VOUT. The dependence of the static characteristics and the dynamic characteristics of the ultrasonic element USMX and the ultrasonic transmitting / receiving element USM1 is cancelled.

さらに、擬似超音波素子ＵＳＭＸは、超音波送受信素子ＵＳＭ１と温度特性が同一であることが望ましい。すなわち、擬似超音波素子ＵＳＭＸは、図２に示すように、抵抗ＲａとコンデンサＣａ，Ｃｂ，コイルＬａの直列回路との並列回路などの受動素子からなる等化回路により構成した上で、その温度特性をさらに超音波送受信素子ＵＳＭ１の温度特性と一致させる。このようにすれば、超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮと擬似超音波素子ＵＳＭＸからの擬似超音波変換信号ＶＰとの差動出力を超音波受信信号ＶＯＵＴとすることにより、超音波送受信素子ＵＳＭ１の温度依存性がキャンセルされることになる。 Furthermore, it is desirable that the pseudo ultrasonic element USMX has the same temperature characteristics as the ultrasonic transmission / reception element USM1. That is, as shown in FIG. 2, the pseudo ultrasonic element USMX is configured by an equalization circuit including a passive element such as a parallel circuit of a resistor Ra and a series circuit of capacitors Ca, Cb, and a coil La, and the temperature thereof The characteristics are further matched with the temperature characteristics of the ultrasonic transmitting / receiving element USM1. According to this configuration, the differential output between the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element USM1 and the pseudo ultrasonic conversion signal VP from the pseudo ultrasonic element USMX is used as the ultrasonic reception signal VOUT. The temperature dependence of the transmitting / receiving element USM1 is cancelled.

このように構成された実施例１に係る受信回路では、超音波送受信素子ＵＳＭ１で超音波が受信されると、超音波は機械−電気変換されて超音波変換信号ＶＩＮとしてコンデンサＣ１および抵抗Ｒ１を通じてオペアンプＵ１の非反転入力端子に印加される。また、擬似超音波素子ＵＳＭＸに駆動直後ノイズが発生すると、駆動直後ノイズは擬似超音波変換信号ＶＰとしてコンデンサＣ２および抵抗Ｒ３を通じてオペアンプＵ１の非反転入力端子に印加される。オペアンプＵ１は、非反転入力端子に印加され超音波変換信号ＶＩＮと、反転入力端子に印加された擬似超音波変換信号ＶＰとを入力し、抵抗Ｒ１，Ｒ２で決まる増幅率で増幅して増幅信号を出力し、増幅信号をさらにオペアンプＵ２が抵抗Ｒ７，Ｒ８で決まる増幅率で増幅して、超音波受信信号ＶＯＵＴとして出力する。 In the receiving circuit according to the first embodiment configured as described above, when an ultrasonic wave is received by the ultrasonic wave transmitting / receiving element USM1, the ultrasonic wave is mechanical-electrically converted and converted into an ultrasonic conversion signal VIN through the capacitor C1 and the resistor R1. Applied to the non-inverting input terminal of the operational amplifier U1. Further, when noise immediately after driving occurs in the pseudo ultrasonic element USMX, the noise immediately after driving is applied to the non-inverting input terminal of the operational amplifier U1 through the capacitor C2 and the resistor R3 as the pseudo ultrasonic conversion signal VP. The operational amplifier U1 receives the ultrasonic conversion signal VIN applied to the non-inverting input terminal and the pseudo ultrasonic conversion signal VP applied to the inverting input terminal, and amplifies the amplified signal by an amplification factor determined by the resistors R1 and R2. The operational amplifier U2 further amplifies the amplified signal at an amplification factor determined by the resistors R7 and R8, and outputs it as an ultrasonic reception signal VOUT.

実施例１に係る受信回路では、超音波送受信素子ＵＳＭ１からの超音波変換信号ＶＩＮと擬似超音波素子ＵＳＭＸからの擬似超音波変換信号ＶＰとの差動出力を超音波受信信号ＶＯＵＴとすることにより、図３に示すように、超音波変換信号ＶＩＮに含まれる駆動直後ノイズと、擬似超音波変換信号ＶＰに含まれる駆動直後ノイズとがキャンセルされて、超音波受信信号ＶＯＵＴに駆動直後ノイズが出力されなくなる、あるいは駆動直後ノイズが抑制されるという効果が得られる。 In the receiving circuit according to the first embodiment, the differential output between the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element USM1 and the pseudo ultrasonic conversion signal VP from the pseudo ultrasonic element USMX is used as the ultrasonic reception signal VOUT. 3, the noise immediately after driving included in the ultrasonic conversion signal VIN and the noise immediately after driving included in the pseudo ultrasonic wave conversion signal VP are canceled, and the noise immediately after driving is output to the ultrasonic wave reception signal VOUT. It is possible to obtain an effect that noise is suppressed or noise immediately after driving is suppressed.

図４は、本発明の実施例２に係る受信回路の構成を示す回路図である。本実施例２に係る受信回路は、図１に示した実施例１に係る受信回路に対して、超音波送受信素子ＵＳＭ１での機械−電気変換出力を増幅する超音波変換信号増幅回路１３と、擬似超音波素子ＵＳＭＸの出力のみを増幅する擬似超音波変換信号増幅回路１４とを設け、両回路の増幅信号の差動出力を超音波受信信号ＶＯＵＴとするようにしたものである。 FIG. 4 is a circuit diagram illustrating a configuration of a receiving circuit according to the second embodiment of the present invention. The receiving circuit according to the second embodiment includes an ultrasonic conversion signal amplifying circuit 13 that amplifies the mechanical-electric conversion output of the ultrasonic transmitting / receiving element USM1 with respect to the receiving circuit according to the first embodiment illustrated in FIG. A pseudo ultrasonic conversion signal amplification circuit 14 for amplifying only the output of the pseudo ultrasonic element USMX is provided, and the differential output of the amplified signals of both circuits is set as the ultrasonic reception signal VOUT.

このように構成された実施例２に係る受信回路では、超音波変換信号増幅回路１３により超音波送受信素子ＵＳＭ１の出力を増幅して超音波変換信号ＶＩＮとするとともに、擬似超音波変換信号増幅回路１４により擬似超音波素子ＵＳＭＸの出力を増幅して擬似超音波変換信号ＶＰとして、それらの差動出力を超音波受信信号ＶＯＵＴとするようにしたので、十分に大きな値の超音波受信信号ＶＯＵＴが得られる。 In the receiving circuit according to the second embodiment configured as described above, the ultrasonic conversion signal amplification circuit 13 amplifies the output of the ultrasonic transmission / reception element USM1 to obtain the ultrasonic conversion signal VIN, and the pseudo ultrasonic conversion signal amplification circuit. 14, the output of the pseudo ultrasonic element USMX is amplified as the pseudo ultrasonic conversion signal VP, and the differential output thereof is set as the ultrasonic reception signal VOUT. Therefore, the ultrasonic reception signal VOUT having a sufficiently large value is obtained. can get.

図５は、本発明の実施例３に係る超音波流量計１の構成を示す回路ブロック図である。本実施例３に係る超音波流量計１は、一般住宅用ガスメータ等として用いられるものを一例としており、一対の超音波送受信素子２ａ，２ｂと、流量測定用の流路３と、順／逆切替手段４と、送信回路５と、受信回路６と、擬似超音波素子７と、ゼロクロスポイント検出手段８と、時間計測手段９とから、その主要部が構成されている。 FIG. 5 is a circuit block diagram showing the configuration of the ultrasonic flowmeter 1 according to the third embodiment of the present invention. The ultrasonic flow meter 1 according to the third embodiment is an example used for a general residential gas meter or the like, and includes a pair of ultrasonic transmission / reception elements 2a and 2b, a flow rate measuring channel 3, and forward / reverse. The switching means 4, the transmission circuit 5, the reception circuit 6, the pseudo ultrasonic element 7, the zero cross point detection means 8, and the time measurement means 9 constitute the main part.

一対の超音波送受信素子２ａ，２ｂは、超音波の送信および受信が可能な超音波送受信素子で形成されている。 The pair of ultrasonic transmission / reception elements 2a and 2b is formed of an ultrasonic transmission / reception element capable of transmitting and receiving ultrasonic waves.

流路３には、ガス等の計測流体が流れ方向である左から右に流通（平均流速Ｖ）している。流路３の壁側には、流れ方向上手側に超音波送受信素子２aが取り付けられ、流れ方向下手側に超音波送受信素子２bが取り付けられている。なお、超音波送受信素子２ａと超音波送受信素子２ｂとの取り付け角（流路３の軸心線と超音波送受信素子２aおよび２bの振動面に対する垂直線とのなす角をいう）をθとする。 In the flow path 3, a measurement fluid such as gas circulates (average velocity V) from left to right in the flow direction. On the wall side of the flow path 3, an ultrasonic transmission / reception element 2 a is attached on the upper side in the flow direction, and an ultrasonic transmission / reception element 2 b is attached on the lower side in the flow direction. Note that θ is an attachment angle between the ultrasonic transmission / reception element 2a and the ultrasonic transmission / reception element 2b (referred to as an angle between the axis of the flow path 3 and a vertical line to the vibration plane of the ultrasonic transmission / reception elements 2a and 2b). .

流路３は、少なくとも超音波送受信素子２ａ−超音波送受信素子２ｂ間において、流れ方向に沿って軸断面の形状および断面積が同一に形成されている。計測流体がガスの場合、流路３の軸断面形状は壁面により閉鎖された空間を形成するものであればよく、例えば、円形状，楕円形状，正方形形状，矩形状などのいずれを採用してもよい。 The flow path 3 has the same axial cross-sectional shape and cross-sectional area along the flow direction at least between the ultrasonic transmission / reception element 2a and the ultrasonic transmission / reception element 2b. When the measurement fluid is a gas, the axial cross-sectional shape of the flow path 3 may be any shape that forms a space closed by a wall surface. For example, any one of a circular shape, an elliptical shape, a square shape, a rectangular shape, etc. may be adopted. Also good.

順／逆切替手段４は、例えば、流路３内の流れ方向が左から右であるとして、流れに沿う方向（順方向）に超音波を送信するときには、流れ方向上手側の超音波送受信素子２ａを送信側とするために、送信回路５と超音波送受信素子２ａとを接続するとともに、流れ方向下手側の超音波送受信素子２ｂを受信側にするために、受信回路６と超音波送受信素子２ｂとを接続する。一方、流れに逆らう方向（逆方向）に超音波を送信するときには、流れ方向下手側の超音波送受信素子２ｂを送信側とするために、送信回路５と超音波送受信素子２ｂとを接続するとともに、流れ方向上手側の超音波送受信素子２ａを受信側にするために、受信回路６と超音波送受信素子２ａとを接続する。 For example, the forward / reverse switching means 4 assumes that the flow direction in the flow path 3 is from left to right, and transmits ultrasonic waves in the direction along the flow (forward direction). In order to make 2a the transmitting side, the transmitting circuit 5 and the ultrasonic transmitting / receiving element 2a are connected, and in order to make the ultrasonic transmitting / receiving element 2b on the lower side in the flow direction the receiving side, the receiving circuit 6 and the ultrasonic transmitting / receiving element 2b is connected. On the other hand, when transmitting an ultrasonic wave in the direction opposite to the flow (reverse direction), the transmission circuit 5 and the ultrasonic transmission / reception element 2b are connected so that the ultrasonic transmission / reception element 2b on the lower side in the flow direction is the transmission side. The receiving circuit 6 and the ultrasonic transmitting / receiving element 2a are connected so that the ultrasonic transmitting / receiving element 2a on the upper side in the flow direction becomes the receiving side.

送信回路５は、超音波の駆動パルスを送信側の超音波送受信素子２ａまたは２ｂに印加することにより、超音波を流路３内に送信（放射）させる。 The transmission circuit 5 transmits (radiates) ultrasonic waves into the flow path 3 by applying ultrasonic drive pulses to the ultrasonic transmission / reception element 2a or 2b on the transmission side.

受信回路６は、差動増幅器１１と、増幅回路１２と、順／逆切替スイッチ１５とを含んで構成されている。 The receiving circuit 6 includes a differential amplifier 11, an amplifier circuit 12, and a forward / reverse switch 15.

図６は、実施例３に係る超音波流量計１における受信回路６をより詳細に示す回路図である。本実施例３に係る受信回路６は、オペアンプＵ１を主体とする差動増幅器１１と、オペアンプＵ２を主体とする反転増幅器（増幅回路）１２と、超音波送受信素子２ａ，２ｂの出力を選択的に差動増幅器１１に接続する順／逆切替スイッチ１５とを含んで構成されている。オペアンプＵ１の反転入力端子は、抵抗Ｒ１，コンデンサＣ１および順／逆切替スイッチ１５を通じて一端を接地された超音波送受信素子２ａ，２ｂに接続されているとともに、抵抗Ｒ２を通じてオペアンプＵ１の出力端子ＯＵＴに接続されている。超音波送受信素子２ａ，２ｂには、順／逆切替スイッチ１５を介して、一端が接地された抵抗Ｒ５が並列に接続されている。また、オペアンプＵ１の非反転入力端子は、抵抗Ｒ３およびコンデンサＣ２を通じて一端を接地された擬似超音波素子７に接続されているとともに抵抗Ｒ４を通じて接地されている。擬似超音波素子７には、抵抗Ｒ６が並列に接続されている。オペアンプＵ１の出力端子ＯＵＴは、抵抗Ｒ７を通じてオペアンプＵ２の非反転入力端子に接続されており、オペアンプＵ２の反転入力端子は抵抗Ｒ８を通じてオペアンプＵ２の出力端子ＯＵＴに接続されている。オペアンプＵ２の非反転入力端子は、抵抗Ｒ９を通じて接地されている。オペアンプＵ２の出力端子ＯＵＴからは、差動出力である超音波受信信号ＶＯＵＴが出力される。なお、図６中、符号ＶＤＤは電源電圧、ＶＳＳはマイナス電源電圧を示す。 FIG. 6 is a circuit diagram illustrating the receiving circuit 6 in the ultrasonic flowmeter 1 according to the third embodiment in more detail. The receiving circuit 6 according to the third embodiment selectively outputs the differential amplifier 11 mainly composed of the operational amplifier U1, the inverting amplifier (amplifier circuit) 12 mainly composed of the operational amplifier U2, and the ultrasonic transmitting / receiving elements 2a and 2b. And a forward / reverse changeover switch 15 connected to the differential amplifier 11. The inverting input terminal of the operational amplifier U1 is connected to the ultrasonic transmission / reception elements 2a and 2b whose one ends are grounded through the resistor R1, the capacitor C1, and the forward / reverse switching switch 15, and to the output terminal OUT of the operational amplifier U1 through the resistor R2. It is connected. A resistance R5 having one end grounded is connected in parallel to the ultrasonic transmission / reception elements 2a and 2b via a forward / reverse switch 15. The non-inverting input terminal of the operational amplifier U1 is connected to the pseudo ultrasonic element 7 whose one end is grounded through the resistor R3 and the capacitor C2, and is grounded through the resistor R4. A resistor R6 is connected to the pseudo ultrasonic element 7 in parallel. The output terminal OUT of the operational amplifier U1 is connected to the non-inverting input terminal of the operational amplifier U2 through the resistor R7, and the inverting input terminal of the operational amplifier U2 is connected to the output terminal OUT of the operational amplifier U2 through the resistor R8. The non-inverting input terminal of the operational amplifier U2 is grounded through the resistor R9. An ultrasonic reception signal VOUT, which is a differential output, is output from the output terminal OUT of the operational amplifier U2. In FIG. 6, reference sign VDD indicates a power supply voltage, and VSS indicates a negative power supply voltage.

図５に戻って、増幅回路１２は、超音波受信信号ＶＯＵＴをゼロクロスポイント検出手段８に出力する。 Returning to FIG. 5, the amplifier circuit 12 outputs the ultrasonic reception signal VOUT to the zero cross point detection means 8.

ゼロクロスポイント検出手段８は、増幅回路１２からの超音波受信信号ＶＯＵＴを入力し、例えば、受信した超音波の第３波のゼロクロスポイントを検出し、ゼロクロスポイント検出信号を時間計測手段９に出力する。 The zero cross point detection means 8 receives the ultrasonic reception signal VOUT from the amplifier circuit 12, detects the zero cross point of the received third wave of ultrasonic waves, and outputs the zero cross point detection signal to the time measurement means 9. .

時間計測手段９は、送信回路５から送信開始信号を入力して超音波伝搬時間の計測を開始し、ゼロクロスポイント検出手段８からゼロクロスポイント検出信号を入力して超音波の伝搬時間の計測を終了する。以下、流れ方向上手側の超音波送受信素子２aより流路３内に超音波が送信されてから、流れ方向下手側の超音波送受信素子２ｂで超音波を受信するまでの時間を順方向伝搬時間Ｔｕｄとする。また、流れ方向下手側の超音波送受信素子２ｂより流路３内に超音波が送信されてから、流れ方向上手側の超音波送受信素子２ａで超音波を受信するまでの時間を逆方向伝搬時間Ｔｄｕとする。 The time measuring means 9 inputs the transmission start signal from the transmission circuit 5 and starts measuring the ultrasonic propagation time, and inputs the zero cross point detection signal from the zero cross point detecting means 8 and ends the measurement of the ultrasonic propagation time. To do. Hereinafter, the time from when the ultrasonic wave is transmitted from the ultrasonic transmitting / receiving element 2a on the upper side in the flow direction into the flow path 3 until the ultrasonic wave is received by the ultrasonic transmitting / receiving element 2b on the lower side in the flow direction is the forward propagation time. Let Tud. Also, the time until the ultrasonic wave is received by the ultrasonic wave transmitting / receiving element 2a on the upper side in the flow direction after the ultrasonic wave is transmitted from the ultrasonic wave transmitting / receiving element 2b on the lower side in the flow direction to the flow path 3 is the reverse propagation time. Let Tdu.

次に、このように構成された実施例３に係る超音波流量計１の動作について説明する。 Next, the operation of the ultrasonic flowmeter 1 according to the third embodiment configured as described above will be described.

まず、順／逆切替手段４は、送受切替信号を送信回路５および受信回路６に出力する。いま、流れ方向上手側の超音波送受信素子２aを送信側とし、流れ方向下手側の超音波送受信素子２bを受信側とする送受切替信号が出力されたものとする。 First, the forward / reverse switching means 4 outputs a transmission / reception switching signal to the transmission circuit 5 and the reception circuit 6. It is assumed that a transmission / reception switching signal is output with the ultrasonic transmission / reception element 2a on the upper side in the flow direction as the transmission side and the ultrasonic transmission / reception element 2b on the lower side in the flow direction as the reception side.

送信回路５は、送受切替信号を受信すると、所定数の駆動パルスを送信側の超音波送受信素子２ａに印加する。すると、送信側の超音波送受信素子２ａは、駆動パルスによって駆動され、駆動パルス数の超音波を流路３内に送信する。これと同時に、送信回路５は、送信開始信号を時間計測手段９に出力する。 When receiving the transmission / reception switching signal, the transmission circuit 5 applies a predetermined number of drive pulses to the ultrasonic transmission / reception element 2a on the transmission side. Then, the transmission-side ultrasonic transmission / reception element 2 a is driven by the drive pulse, and transmits ultrasonic waves having the number of drive pulses into the flow path 3. At the same time, the transmission circuit 5 outputs a transmission start signal to the time measuring means 9.

時間計測手段９は、送信回路５からの送信開始信号を受けることにより、超音波の伝搬時間（順方向伝搬時間）Ｔｕｄの計測を開始する。 The time measuring means 9 starts measuring the ultrasonic wave propagation time (forward propagation time) Tud by receiving the transmission start signal from the transmission circuit 5.

送信側の超音波送受信素子２ａから送信された超音波は、流路３の内壁で一旦反射された後に、受信側の超音波送受信素子２ｂに到達する。 The ultrasonic wave transmitted from the transmission-side ultrasonic transmission / reception element 2 a is once reflected by the inner wall of the flow path 3 and then reaches the reception-side ultrasonic transmission / reception element 2 b.

受信側の超音波送受信素子２ｂは、受信した超音波を機械−電気変換し、超音波変換信号ＶＩＮを受信回路６に入力する。 The ultrasonic transmission / reception element 2b on the reception side performs mechanical-electrical conversion on the received ultrasonic wave and inputs an ultrasonic conversion signal VIN to the reception circuit 6.

受信回路６では、超音波送受信素子２ｂからの超音波変換信号ＶＩＮが順／逆切替スイッチ１５を介して差動増幅器１１の反転入力端子に入力され、擬似超音波素子７からの擬似超音波変換信号ＶＰが差動増幅器１１の非反転入力端子に入力されて、差動増幅器１１の出力端子に差動出力が出力される。このとき、超音波変換信号ＶＩＮには駆動直後ノイズおよび超音波変換信号ＶＩＮが含まれ、擬似超音波変換信号ＶＰには駆動直後ノイズのみが含まれるので、駆動直後ノイズがキャンセルされ、超音波変換信号ＶＩＮのみが出力されることになる。次に、増幅回路１２は、差動増幅器１１からの差動出力を入力すると、任意の増幅率で増幅し、超音波受信信号ＶＯＵＴをゼロクロスポイント検出手段８に出力する。 In the reception circuit 6, the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element 2 b is input to the inverting input terminal of the differential amplifier 11 via the forward / reverse switch 15, and the pseudo ultrasonic conversion from the pseudo ultrasonic element 7 is performed. The signal VP is input to the non-inverting input terminal of the differential amplifier 11, and a differential output is output to the output terminal of the differential amplifier 11. At this time, the ultrasonic conversion signal VIN includes the noise immediately after driving and the ultrasonic conversion signal VIN, and the pseudo ultrasonic conversion signal VP includes only the noise immediately after driving, so that the noise immediately after driving is canceled and the ultrasonic conversion is performed. Only the signal VIN is output. Next, when the differential output from the differential amplifier 11 is input, the amplifier circuit 12 amplifies the signal with an arbitrary amplification factor and outputs the ultrasonic reception signal VOUT to the zero cross point detection means 8.

続いて、ゼロクロスポイント検出手段８は、増幅回路１２からの超音波受信信号ＶＯＵＴを入力すると、例えば、先に受信した超音波の第３波のゼロクロスポイントを検出し、ゼロクロスポイント検出信号を時間計測手段９に出力する。 Subsequently, when the ultrasonic reception signal VOUT from the amplifier circuit 12 is input, the zero cross point detection unit 8 detects, for example, the zero cross point of the third wave of the ultrasonic wave received earlier, and measures the time of the zero cross point detection signal. Output to means 9.

次に、時間計測手段９は、ゼロクロスポイント検出手段８からゼロクロスポイント検出信号を入力すると、送信側の超音波送受信素子２aより流路３内に超音波が送信されてから、受信側の超音波送受信素子２ｂで超音波を受信するまでの順方向伝搬時間Ｔｕｄの計測を終了する。 Next, when the time crossing means 9 receives the zero cross point detection signal from the zero cross point detecting means 8, the ultrasonic wave is transmitted from the transmitting side ultrasonic transmitting / receiving element 2a into the flow path 3, and then the receiving side ultrasonic wave is received. The measurement of the forward propagation time Tud until the transmitting / receiving element 2b receives the ultrasonic wave is finished.

流体の流れに逆らう逆方向伝搬時間Ｔｄｕの計測は、流体の流れに沿う順方向伝搬時間Ｔｕｄの計測とは逆の動作をさせればよい。このとき、順／逆切替手段４は、流れ方向下手側の超音波送受信素子２ｂを送信側とし、流れ方向上手側の超音波送受信素子２aを受信側とする送受切替信号を送信回路５および受信回路６に出力する。流れ方向下手側の超音波送受信素子２ｂから超音波を送信し、流れ方向上手側の超音波送受信素子２ａで超音波を検出するまでの逆方向伝搬時間Ｔｄｕを計測する。 The measurement of the backward propagation time Tdu against the fluid flow may be performed in the opposite manner to the measurement of the forward propagation time Tud along the fluid flow. At this time, the forward / reverse switching means 4 transmits and receives a transmission / reception switching signal with the ultrasonic transmission / reception element 2b on the lower side in the flow direction as the transmission side and the ultrasonic transmission / reception element 2a on the upper side in the flow direction as the reception side. Output to circuit 6. An ultrasonic wave is transmitted from the ultrasonic transmission / reception element 2b on the lower side in the flow direction, and the backward propagation time Tdu until the ultrasonic wave is detected by the ultrasonic transmission / reception element 2a on the upper side in the flow direction is measured.

詳しくは、送信回路５は、所定数の駆動パルスを送信側の超音波送受信素子２ｂに印加する。すると、送信側の超音波送受信素子２ｂは、駆動パルスによって駆動され、駆動パルス数の超音波を流路３内に送信する。 Specifically, the transmission circuit 5 applies a predetermined number of driving pulses to the ultrasonic transmission / reception element 2b on the transmission side. Then, the transmission-side ultrasonic transmission / reception element 2 b is driven by the drive pulse, and transmits ultrasonic waves having the number of drive pulses into the flow path 3.

流路３内には、流体の平均流速Ｖが発生しているとすると、送信側の超音波送受信素子２ｂから送信された超音波を受信側の超音波送受信素子２ａで受信する間での時間を、逆方向伝搬時間Ｔｄｕとする。 Assuming that the average flow velocity V of the fluid is generated in the flow path 3, the time between reception of the ultrasonic wave transmitted from the transmitting-side ultrasonic transmitting / receiving element 2 b by the receiving-side ultrasonic transmitting / receiving element 2 a. Is the backward propagation time Tdu.

順方向伝搬時間Ｔｕｄおよび逆方向伝搬時間Ｔｄｕが求められると、超音波流量計１は、流路３の断面積をＳ、超音波送受信素子距離間をＬ、超音波送受信素子２ａと超音波送受信素子２ｂとの取り付け角をθとすると、流速ｖ（ｍ／ｓ）を、数１で求める。 When the forward propagation time Tud and the backward propagation time Tdu are obtained, the ultrasonic flowmeter 1 uses the cross-sectional area of the flow path 3 as S, the distance between the ultrasonic transmission / reception element distances, and the ultrasonic transmission / reception element 2a as an ultrasonic transmission / reception. Assuming that the attachment angle with the element 2b is θ, the flow velocity v (m / s) is obtained by Equation 1.

Figure 2006017568
Figure 2006017568

また、超音波流量計１は、流量Ｑ（ｍ３／ｈ）を、数２で求める。 Moreover, the ultrasonic flowmeter 1 calculates | requires flow volume Q (m < 3 > / h) by Formula 2. FIG.

Figure 2006017568
Figure 2006017568

本実施例３に係る超音波流量計１によれば、超音波送受信素子２ａまたは超音波送受信素子２ｂからの超音波変換信号ＶＩＮと擬似超音波素子７からの擬似超音波変換信号との差動出力を超音波受信信号ＶＯＵＴとすることにより、回路上に発生する駆動直後ノイズが常にキャンセルされ、図３に示したような安定した超音波受信信号ＶＯＵＴが得られる。この結果、駆動直後ノイズ、およびそれ以降のノイズや残響成分が著しく低減される。 According to the ultrasonic flowmeter 1 according to the third embodiment, the differential between the ultrasonic conversion signal VIN from the ultrasonic transmission / reception element 2a or the ultrasonic transmission / reception element 2b and the pseudo ultrasonic conversion signal from the pseudo ultrasonic element 7 is obtained. By setting the output to the ultrasonic reception signal VOUT, noise immediately after driving generated on the circuit is always canceled, and a stable ultrasonic reception signal VOUT as shown in FIG. 3 is obtained. As a result, noise immediately after driving, and subsequent noise and reverberation components are significantly reduced.

また、順／逆切替手段４により流れ方向上手側の超音波送受信素子２ａを受信側とした場合でも、流れ方向下手側の超音波送受信素子２ｂを受信側とした場合でも、受信回路６内では、擬似超音波素子７からの擬似超音波変換信号ＶＰを入力とするようにしたので、超音波送受信素子２ａおよび超音波送受信素子２ｂのそれぞれに対して擬似超音波素子７を設けなくても、１つの擬似超音波素子７で高精度な流量計測が実現可能となる。 Even if the ultrasonic transmission / reception element 2a on the upper side in the flow direction is set as the reception side by the forward / reverse switching means 4, the ultrasonic transmission / reception element 2b on the lower side in the flow direction is set as the reception side. Since the pseudo ultrasonic wave conversion signal VP from the pseudo ultrasonic wave element 7 is input, even if the pseudo ultrasonic wave element 7 is not provided for each of the ultrasonic wave transmitting / receiving element 2a and the ultrasonic wave transmitting / receiving element 2b, Highly accurate flow rate measurement can be realized with one pseudo ultrasonic element 7.

なお、送信回路５と受信回路６との電源を別々にするとよい。そうすることで、超音波の送信時の送信回路５の電源電圧変動が受信回路６に影響を与えにくくなるので、低ノイズの受信回路６となり、その出力である超音波受信信号ＶＯＵＴがより安定したものとなる。 Note that the power supplies of the transmission circuit 5 and the reception circuit 6 may be provided separately. By doing so, the power supply voltage fluctuation of the transmission circuit 5 at the time of ultrasonic transmission becomes less likely to affect the reception circuit 6, so that the low-noise reception circuit 6 is obtained, and the ultrasonic reception signal VOUT that is the output is more stable. Will be.

図７は、本発明の実施例４に係る受信回路の構成を示す回路図である。本実施例４に係る受信回路は、図６に示した実施例３に係る受信回路６に対して、超音波送受信素子２ａまたは超音波送受信素子２ｂでの機械−電気変換出力を増幅する超音波変換信号増幅回路１３と、擬似超音波素子７の出力のみを増幅する擬似超音波変換信号増幅回路１４とを設け、両回路の増幅信号の差動出力を超音波受信信号ＶＯＵＴとするようにしたものである。 FIG. 7 is a circuit diagram showing a configuration of a receiving circuit according to Embodiment 4 of the present invention. The receiving circuit according to the fourth embodiment is an ultrasonic wave that amplifies the mechanical-electrical conversion output of the ultrasonic transmitting / receiving element 2a or the ultrasonic transmitting / receiving element 2b with respect to the receiving circuit 6 according to the third embodiment illustrated in FIG. The conversion signal amplification circuit 13 and the pseudo ultrasonic conversion signal amplification circuit 14 for amplifying only the output of the pseudo ultrasonic element 7 are provided, and the differential output of the amplification signals of both circuits is set as the ultrasonic reception signal VOUT. Is.

このように構成された実施例４に係る受信回路では、超音波変換信号増幅回路１３により超音波送受信素子２ａまたは超音波送受信素子２ｂの出力を増幅して超音波変換信号ＶＩＮとするとともに、擬似超音波変換信号増幅回路１４により擬似超音波素子７の出力を増幅して擬似超音波変換信号ＶＰとして、それらの差動出力を超音波受信信号ＶＯＵＴとするようにしたので、十分に大きな値の超音波受信信号ＶＯＵＴが得られる。 In the receiving circuit according to the fourth embodiment configured as described above, the ultrasonic conversion signal amplification circuit 13 amplifies the output of the ultrasonic transmission / reception element 2a or the ultrasonic transmission / reception element 2b to obtain the ultrasonic conversion signal VIN, Since the output of the pseudo ultrasonic element 7 is amplified by the ultrasonic conversion signal amplification circuit 14 and the differential output is used as the ultrasonic reception signal VOUT as the pseudo ultrasonic conversion signal VP, a sufficiently large value is obtained. An ultrasonic reception signal VOUT is obtained.

なお、本実施例４に係る受信回路においても、図６に示した実施例３に係る受信回路６と同様に、送信回路５の電源と、超音波変換信号増幅回路１３，擬似超音波変換信号増幅回路１４などを含む受信回路６の電源とを別々にするとよい。そうすることで、送信時の送信回路５の電源電圧変動が受信回路６に影響を与えなくなるので、低ノイズの受信回路となり、その出力である超音波受信信号ＶＯＵＴが安定したものとなる。 In the receiving circuit according to the fourth embodiment, similarly to the receiving circuit 6 according to the third embodiment illustrated in FIG. 6, the power supply of the transmitting circuit 5, the ultrasonic conversion signal amplification circuit 13, and the pseudo ultrasonic conversion signal are used. The power supply of the receiving circuit 6 including the amplifier circuit 14 and the like may be provided separately. By doing so, the power supply voltage fluctuation of the transmission circuit 5 at the time of transmission does not affect the reception circuit 6, so that a low-noise reception circuit is obtained, and the ultrasonic reception signal VOUT that is the output becomes stable.

ところで、図５に示した実施例３に係る超音波流量計１として、超音波送受信素子２ａと超音波送受信素子２ｂとを流路３の内壁を挟んで対向するように配置した例（一対の超音波送受信素子２ａ，２ｂをＶ字型に配置した例）を示したが、本発明の適用がこのような配置の超音波流量計１に限定されるわけでない。例えば、一対の超音波送受信素子を直接対向するように配置した超音波流量計においても、本発明が同様に適用できることはいうまでもない。 By the way, as the ultrasonic flowmeter 1 according to the third embodiment shown in FIG. 5, an example in which the ultrasonic transmission / reception element 2a and the ultrasonic transmission / reception element 2b are arranged to face each other across the inner wall of the flow path 3 (a pair of pairs). Although an example in which the ultrasonic transmission / reception elements 2a and 2b are arranged in a V shape is shown, the application of the present invention is not limited to the ultrasonic flowmeter 1 having such an arrangement. For example, it goes without saying that the present invention can be similarly applied to an ultrasonic flowmeter in which a pair of ultrasonic transmitting / receiving elements are arranged so as to face each other directly.

以上、本発明の実施例を説明したが、これらはあくまで例示にすぎず、本発明はこれらに限定されるものではなく、特許請求の範囲の趣旨を逸脱しない限りにおいて、当業者の知識に基づく種々の変更が可能である。 As mentioned above, although the Example of this invention was described, these are only illustrations to the last, and this invention is not limited to these, Based on the knowledge of those skilled in the art, unless it deviates from the meaning of a Claim Various changes are possible.

本発明の実施例１に係る受信回路を示す回路図。1 is a circuit diagram showing a receiving circuit according to Embodiment 1 of the present invention. 図１中の擬似超音波素子の変形例を示す回路図。The circuit diagram which shows the modification of the pseudo | simulation ultrasonic element in FIG. 図１中の超音波受信信号の波形図。The wave form diagram of the ultrasonic reception signal in FIG. 本発明の実施例２に係る受信回路を示す回路図。FIG. 6 is a circuit diagram showing a receiving circuit according to Embodiment 2 of the present invention. 本発明の実施例３に係る超音波流量計の構成を示すブロック図。The block diagram which shows the structure of the ultrasonic flowmeter which concerns on Example 3 of this invention. 図５中の受信回路の回路図。FIG. 6 is a circuit diagram of the receiving circuit in FIG. 5. 本発明の実施例４に係る受信回路を示す回路図。FIG. 6 is a circuit diagram showing a receiving circuit according to Embodiment 4 of the present invention. 従来の受信回路を示す回路図。The circuit diagram which shows the conventional receiving circuit. 従来の受信回路における超音波受信信号の波形図。The wave form diagram of the ultrasonic reception signal in the conventional receiving circuit.

符号の説明Explanation of symbols

１ 超音波流量計
２ａ，２ｂ 超音波送受信素子
３ 流路
４ 順／逆切替手段
５ 送信回路
６ 受信回路
７ 擬似超音波素子
８ ゼロクロスポイント検出手段
９ 時間計測手段
１１ 差動増幅器
１２ 増幅回路（反転増幅器）
１３ 超音波変換信号増幅回路
１４ 擬似超音波変換信号増幅回路
１５ 順／逆切替スイッチ
ＵＳＭ１，ＵＳＭ２ 超音波送受信素子
ＵＳＭＸ 擬似超音波素子 DESCRIPTION OF SYMBOLS 1 Ultrasonic flowmeter 2a, 2b Ultrasonic transmission / reception element 3 Flow path 4 Forward / reverse switching means 5 Transmission circuit 6 Reception circuit 7 Pseudo ultrasonic element 8 Zero cross point detection means 9 Time measurement means 11 Differential amplifier 12 Amplification circuit (inversion) amplifier)
13 Ultrasonic conversion signal amplification circuit 14 Pseudo ultrasonic conversion signal amplification circuit 15 Forward / reverse switch USM1, USM2 Ultrasonic transmission / reception element USMX Pseudo ultrasonic element

Claims (9)

流体を通過させる流路内の流体の流れ方向上手側および下手側に取り付けられた一対の超音波送受信素子と、
前記一対の超音波送受信素子の一方を駆動して超音波を送信させる送信回路と、
超音波を直接受信しない擬似超音波素子と、
前記一対の超音波送受信素子の他方で受信した超音波の超音波変換信号と、前記擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力する受信回路と
を有することを特徴とする超音波流量計。 A pair of ultrasonic transmitting / receiving elements attached to the upper and lower sides of the flow direction of the fluid in the flow path through which the fluid passes;
A transmission circuit for driving one of the pair of ultrasonic transmission / reception elements to transmit ultrasonic waves;
A pseudo ultrasonic element that does not receive ultrasonic waves directly;
A receiving circuit that outputs, as an ultrasonic reception signal, a differential output between the ultrasonic conversion signal of the ultrasonic wave received by the other of the pair of ultrasonic transmission / reception elements and the pseudo ultrasonic conversion signal generated by the pseudo ultrasonic element; An ultrasonic flowmeter characterized by comprising: 流体を通過させる流路内の流体の流れ方向上手側および下手側に取り付けられた一対の超音波送受信素子と、
前記一対の超音波送受信素子の一方を送信側、他方を受信側として切り替える順／逆切替手段と、
前記送信側の超音波送受信素子を駆動して超音波を送信させる送信回路と、
超音波を直接受信しない擬似超音波素子と、
前記受信側の超音波送受信素子で受信した超音波の超音波変換信号と、前記擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力する受信回路と
を有することを特徴とする超音波流量計。 A pair of ultrasonic transmitting / receiving elements attached to the upper and lower sides of the flow direction of the fluid in the flow path through which the fluid passes;
Forward / reverse switching means for switching one of the pair of ultrasonic transmitting / receiving elements as a transmission side and the other as a reception side;
A transmission circuit for driving the transmission-side ultrasonic transmission / reception element to transmit ultrasonic waves;
A pseudo ultrasonic element that does not receive ultrasonic waves directly;
A receiving circuit that outputs, as an ultrasonic reception signal, a differential output between the ultrasonic conversion signal of the ultrasonic wave received by the ultrasonic transmission / reception element on the receiving side and the pseudo ultrasonic conversion signal generated by the pseudo ultrasonic element; An ultrasonic flowmeter characterized by comprising: 前記擬似超音波素子が、超音波の送信および受信が可能な超音波送受信素子でなることを特徴とする請求項１または請求項２に記載の超音波流量計。 The ultrasonic flowmeter according to claim 1, wherein the pseudo ultrasonic element is an ultrasonic transmission / reception element capable of transmitting and receiving ultrasonic waves. 前記擬似超音波素子が、超音波送受信素子などの圧電体以外の受動素子で構成され、かつ前記一対の超音波送受信素子と電気的特性を同一にしたことを特徴とする請求項１または請求項２記載の超音波流量計。 The pseudo ultrasonic element is composed of a passive element other than a piezoelectric body, such as an ultrasonic transmission / reception element, and has the same electrical characteristics as the pair of ultrasonic transmission / reception elements. 2. The ultrasonic flowmeter according to 2. 前記擬似超音波素子が、前記一対の超音波送受信素子と温度特性が同一であることを特徴とする請求項１ないし請求項４のいずれかに記載の超音波流量計。 The ultrasonic flowmeter according to any one of claims 1 to 4, wherein the pseudo ultrasonic element has the same temperature characteristics as the pair of ultrasonic transmission / reception elements. 前記受信回路が、前記一対の超音波送受信素子の一方からの超音波変換信号を任意の増幅率で増幅する超音波変換信号増幅回路と、前記擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅する擬似超音波変換信号増幅回路とを備え、前記超音波変換信号増幅回路の増幅信号および前記擬似超音波変換信号増幅回路の増幅信号の差動出力を超音波受信信号として出力することを特徴とする請求項１ないし請求項５のいずれかに記載の超音波流量計。 The receiving circuit arbitrarily converts an ultrasonic conversion signal amplification circuit that amplifies an ultrasonic conversion signal from one of the pair of ultrasonic transmission / reception elements at an arbitrary amplification factor, and a pseudo ultrasonic conversion signal from the pseudo ultrasonic element. And a differential output of the amplification signal of the ultrasonic conversion signal amplification circuit and the amplification signal of the pseudo ultrasonic conversion signal amplification circuit is output as an ultrasonic reception signal. The ultrasonic flowmeter according to claim 1, wherein the ultrasonic flowmeter is provided. 前記送信回路の電源と前記受信回路の電源とを別々にしたことを特徴とする請求項１ないし請求項６のいずれかに記載の超音波流量計。 The ultrasonic flowmeter according to any one of claims 1 to 6, wherein a power source of the transmission circuit and a power source of the reception circuit are separately provided. 超音波送受信素子で受信した超音波の超音波変換信号と、超音波を直接受信しない擬似超音波素子で発生した擬似超音波変換信号との差動出力を超音波受信信号として出力することを特徴とする受信回路。 The differential output between the ultrasonic conversion signal of the ultrasonic wave received by the ultrasonic transmission / reception element and the pseudo ultrasonic conversion signal generated by the pseudo ultrasonic element that does not directly receive the ultrasonic wave is output as an ultrasonic reception signal. A receiving circuit. 前記超音波送受信素子からの超音波変換信号を任意の増幅率で増幅する超音波変換信号増幅回路と、前記擬似超音波素子からの擬似超音波変換信号を任意の増幅率で増幅する擬似超音波変換信号増幅回路とを備え、前記超音波変換信号増幅回路の増幅信号および前記擬似超音波変換信号増幅回路の増幅信号の差動出力を超音波受信信号として出力することを特徴とする請求項８に記載の受信回路。 An ultrasonic conversion signal amplification circuit that amplifies an ultrasonic conversion signal from the ultrasonic transmission / reception element at an arbitrary amplification factor, and a pseudo ultrasonic wave that amplifies a pseudo ultrasonic conversion signal from the pseudo ultrasonic element at an arbitrary amplification factor 9. A conversion signal amplification circuit, wherein the differential output of the amplification signal of the ultrasonic conversion signal amplification circuit and the amplification signal of the pseudo ultrasonic conversion signal amplification circuit is output as an ultrasonic reception signal. The receiving circuit described in 1.
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JP2010501874A (en) * 2006-09-05 2010-01-21 コンチネンタル オートモーティヴ ゲゼルシャフト ミット ベシュレンクテル ハフツング Circuit device for operating the sound wave transducer arranged at the end of the measurement section in both directions
JP5190825B2 (en) * 2006-11-13 2013-04-24 国立大学法人京都工芸繊維大学 Image reconstruction apparatus, image reconstruction method, image reconstruction program, and CT apparatus
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JP2013242806A (en) * 2012-05-22 2013-12-05 Kyocera Corp Electronic apparatus
US10209791B2 (en) 2012-05-22 2019-02-19 Kyocera Corporation Electronic device and panel device
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JPWO2019069751A1 (en) * 2017-10-06 2020-11-26 株式会社瑞光 Composite sheet manufacturing equipment and manufacturing method
CN117168583A (en) * 2023-10-31 2023-12-05 成都千嘉科技股份有限公司 Zero-crossing detection method and detection device for gas meter
CN117168583B (en) * 2023-10-31 2024-01-23 成都千嘉科技股份有限公司 Zero-crossing detection method and detection device for gas meter

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