JP6652840B2 - Ultrasonic flow meter - Google Patents
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本発明は、超音波流量計に係り、特に流量精度の健全性を判定する技術に関するものである。 The present invention relates to an ultrasonic flowmeter, and more particularly to a technique for determining soundness of flow accuracy.
超音波を用いて流量を計測する超音波流量計が知られている。超音波流量計における計測方法は大きく分けてゼロクロス法と相関法の2方式に分かれる。図15は超音波流量計の計測原理を説明する断面図である。配管1を流れる流体2の流速をV、配管1に設けられた超音波センサ3と超音波センサ4間の伝搬距離をL、超音波センサ3と超音波センサ4とを結ぶ線分が管軸5と成す角をθ、音速をCとすると、超音波センサ3から超音波センサ4までの順方向(流体2が流れる方向)の超音波の伝搬時間t1、超音波センサ4から超音波センサ3までの逆方向の超音波の伝搬時間t2は次式のように表すことができる。
t1=L/(C+Vcosθ) ・・・(1)
t2=L/(C−Vcosθ) ・・・(2)
An ultrasonic flowmeter that measures a flow rate using ultrasonic waves is known. The measuring method in the ultrasonic flow meter is roughly divided into two methods, a zero cross method and a correlation method. FIG. 15 is a cross-sectional view illustrating the measurement principle of the ultrasonic flowmeter. V is the flow velocity of the fluid 2 flowing through the pipe 1, L is the propagation distance between the ultrasonic sensors 3 and 4 provided in the pipe 1, and the line connecting the ultrasonic sensors 3 and 4 is the pipe axis. Assuming that the angle formed with 5 is θ and the sound velocity is C, the propagation time t 1 of the ultrasonic wave in the forward direction (the direction in which the fluid 2 flows) from the ultrasonic sensor 3 to the ultrasonic sensor 4, and the ultrasonic sensor 4 The propagation time t 2 of the ultrasonic wave in the reverse direction up to 3 can be expressed by the following equation.
t 1 = L / (C + Vcos θ) (1)
t 2 = L / (C−Vcos θ) (2)
ゼロクロス法では、超音波センサ3と超音波センサ4のそれぞれから超音波信号を送出して伝搬時間t1,t2を計測し、流体2の流速Vと流量Qを以下のように算出する(特許文献1参照)。
V=(t1−t2)L/(2t1t2) ・・・(3)
Q=SV/k ・・・(4)
In the zero-cross method, the ultrasonic signals are transmitted from the ultrasonic sensors 3 and 4 to measure the propagation times t 1 and t 2 , and the flow velocity V and the flow rate Q of the fluid 2 are calculated as follows ( Patent Document 1).
V = (t 1 −t 2 ) L / (2t 1 t 2 ) (3)
Q = SV / k (4)
式(4)におけるSは配管1の断面積、kは所定の流量補正係数である。伝搬時間t1は、超音波センサ3から超音波信号を送出したときから、超音波センサ4で受信した図16(A)のような超音波受信信号Su→dの最初の受信パルスが立ち上がるまでの時間である。同様に、伝搬時間t2は、超音波センサ4から超音波信号を送出したときから、超音波センサ3で受信した図16(A)のような超音波受信信号Sd→uの最初の受信パルスが立ち上がるまでの時間である。実際には、最初の受信パルスの立ち上がり時間の検出が困難なため、受信波形とx軸(時間軸)との交点であるゼロクロス点から伝搬時間t1,t2を算出している。 In the equation (4), S is a sectional area of the pipe 1, and k is a predetermined flow rate correction coefficient. At the propagation time t 1 , the first reception pulse of the ultrasonic reception signal Su → d as shown in FIG. 16A received by the ultrasonic sensor 4 rises from the transmission of the ultrasonic signal from the ultrasonic sensor 3. Until the time. Similarly, the propagation time t 2 is the time from when the ultrasonic sensor 4 sends out the ultrasonic signal to the first reception of the ultrasonic reception signal S d → u as shown in FIG. It is the time until the pulse rises. Actually, since it is difficult to detect the rise time of the first received pulse, the propagation times t 1 and t 2 are calculated from the zero cross point, which is the intersection of the received waveform and the x-axis (time axis).
一方、相関法では、順方向と逆方向の超音波の伝搬時間差Δtを計測し、流体2の流速Vと流量Qを以下のように算出する(特許文献2参照)。
V≒C2Δt/(2Lcosθ) ・・・(5)
Q=SV/k≒SC2Δt/(2kLcosθ) ・・・(6)
On the other hand, in the correlation method, the propagation time difference Δt between the forward and backward ultrasonic waves is measured, and the flow velocity V and the flow rate Q of the fluid 2 are calculated as follows (see Patent Document 2).
V ≒ C 2 Δt / (2Lcosθ) (5)
Q = SV / k ≒ SC 2 Δt / ( 2 kL cos θ) (6)
伝搬時間差Δtは、受信波形から直接求める。具体的には、超音波センサ4で受信した図16(B)のような超音波受信信号Su→dと超音波センサ3で受信した図16(B)のような超音波受信信号Sd→uのそれぞれをサンプリングして、超音波受信信号Su→dの波形データと超音波受信信号Sd→uの波形データとの相互相関演算を行い、相関関数から伝搬時間差Δtを求める。 The propagation time difference Δt is obtained directly from the received waveform. Specifically, ultrasonic reception signal S d as shown in FIG. 16 received by the ultrasonic wave reception signal S u → d and the ultrasonic sensor 3 as shown in FIG. 16 received by the ultrasonic sensor 4 (B) (B) → u is sampled, a cross-correlation operation is performed between the waveform data of the ultrasonic reception signal S u → d and the waveform data of the ultrasonic reception signal S d → u , and a propagation time difference Δt is obtained from the correlation function.
ところで、超音波流量計では、配管に汚物等が付着した場合に超音波受信信号が減衰することや、超音波流量計が動作することによりその動作に由来するノイズが増加することが知られている。意図しないノイズが計測される超音波受信信号に重畳すると、流量誤差が発生する可能性があり、また最悪の場合には計測不可の状態になる可能性もある。そのためノイズを検出することは、正しい計測をする上で非常に重要である。 By the way, in the ultrasonic flow meter, it is known that the ultrasonic reception signal is attenuated when contaminants or the like adhere to the pipe, and that the operation of the ultrasonic flow meter increases the noise derived from the operation. I have. When the unintended noise is superimposed on the measured ultrasonic reception signal, a flow rate error may occur, and in the worst case, a measurement may not be possible. Therefore, detecting noise is very important for correct measurement.
そこで、計測に悪影響があるノイズを検出できる超音波流量計が提案されている(特許文献3参照)。特許文献3に開示された超音波流量計は、受信波形の特徴値を検出することで受信波形の健全性を判断している。 Therefore, an ultrasonic flowmeter capable of detecting noise that has an adverse effect on measurement has been proposed (see Patent Document 3). The ultrasonic flow meter disclosed in Patent Literature 3 determines the soundness of a received waveform by detecting a characteristic value of the received waveform.
しかしながら、特許文献3に開示された超音波流量計では、超音波受信信号を増幅する増幅部の実増幅率と、流体の種類、流体の温度、および流体の圧力の組み合わせにより決定される適正な理論増幅率とを比較して、理論増幅率と実増幅率との差異が所定以上の場合に、ノイズが発生していると判定するが、流体の温度と圧力を取得しなければならないため、超音波流量計の構成が複雑になってしまうという問題点があった。また、流体の種類と流体の温度と流体の圧力の様々な組み合わせについて対応する理論増幅率を登録したデータベースを予め作成しておく必要があり、データベースの作成に手間がかかるという問題点があった。 However, in the ultrasonic flow meter disclosed in Patent Literature 3, an appropriate amplification ratio determined by a combination of the actual amplification factor of the amplification unit that amplifies the ultrasonic reception signal, the type of fluid, the temperature of the fluid, and the pressure of the fluid. Comparing with the theoretical amplification factor, if the difference between the theoretical amplification factor and the actual amplification factor is equal to or more than a predetermined value, it is determined that noise has occurred, but it is necessary to obtain the temperature and pressure of the fluid, There is a problem that the configuration of the ultrasonic flowmeter becomes complicated. In addition, it is necessary to create a database in which the theoretical amplification factors corresponding to various combinations of the type of fluid, the temperature of the fluid, and the pressure of the fluid are registered in advance, and there is a problem that it takes time to create the database. .
本発明は、上記課題を解決するためになされたもので、流量精度の健全性を簡単な構成で判定することができる超音波流量計を提供することを目的とする。 The present invention has been made to solve the above problems, and has as its object to provide an ultrasonic flowmeter that can determine the soundness of flow accuracy with a simple configuration.
本発明の超音波流量計は、測定対象の流体が流れる配管と、この配管の上流と下流に配置された1対の超音波センサと、上流側の前記超音波センサから送出され下流側の前記超音波センサで受信された第1の超音波受信信号の最大値と下流側の前記超音波センサから送出され上流側の前記超音波センサで受信された第2の超音波受信信号の最大値との差の絶対値、または前記第1の超音波受信信号の最小値と前記第2の超音波受信信号の最小値との差の絶対値を算出する強度差算出手段と、前記第1の超音波受信信号と前記第2の超音波受信信号の伝搬時間差と、前記強度差算出手段が算出した強度差の絶対値との乗算値を算出する乗算値算出手段と、この乗算値算出手段が算出した乗算値が所定の許容強度差より大きい場合に、警報を出力する比較手段とを備えることを特徴とするものである。 The ultrasonic flow meter according to the present invention includes a pipe through which a fluid to be measured flows, a pair of ultrasonic sensors arranged upstream and downstream of the pipe, and the downstream side ultrasonic sensor sent from the upstream ultrasonic sensor. The maximum value of the first ultrasonic reception signal received by the ultrasonic sensor and the maximum value of the second ultrasonic reception signal transmitted from the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side An intensity difference calculating means for calculating an absolute value of a difference between the first and second ultrasonic reception signals and an absolute value of a difference between the minimum value of the second ultrasonic reception signal and the minimum value of the second ultrasonic reception signal; A multiplication value calculating means for calculating a multiplication value of a propagation time difference between the sound wave reception signal and the second ultrasonic reception signal and an absolute value of the intensity difference calculated by the intensity difference calculation means; If the multiplied value is larger than the specified allowable difference, an alarm is output. It is characterized in further comprising a comparing means that.
また、本発明の超音波流量計は、測定対象の流体が流れる配管と、この配管の上流と下流に配置された1対の超音波センサと、上流側の前記超音波センサから送出され下流側の前記超音波センサで受信された第1の超音波受信信号の振幅と下流側の前記超音波センサから送出され上流側の前記超音波センサで受信された第2の超音波受信信号の振幅との差の絶対値を算出する振幅差算出手段と、前記第1の超音波受信信号と前記第2の超音波受信信号の伝搬時間差と、前記振幅差算出手段が算出した振幅差の絶対値との乗算値を算出する乗算値算出手段と、この乗算値算出手段が算出した乗算値が所定の許容振幅差より大きい場合に、警報を出力する比較手段とを備えることを特徴とするものである。
また、本発明の超音波流量計の1構成例において、前記乗算値算出手段は、前記第1の超音波受信信号および前記第2の超音波受信信号の波形データ相互の相関関数から前記伝搬時間差を求めることを特徴とするものである。
Further, the ultrasonic flowmeter of the present invention comprises a pipe through which a fluid to be measured flows, a pair of ultrasonic sensors arranged upstream and downstream of the pipe, and a downstream side sent from the upstream ultrasonic sensor. The amplitude of the first ultrasonic reception signal received by the ultrasonic sensor and the amplitude of the second ultrasonic reception signal transmitted from the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side Amplitude difference calculating means for calculating the absolute value of the difference, the propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and the absolute value of the amplitude difference calculated by the amplitude difference calculation means And a comparing means for outputting an alarm when the multiplied value calculated by the multiplied value calculating means is larger than a predetermined allowable amplitude difference. .
Additionally, in an example of an ultrasonic flowmeter of the present invention, the multiplication value calculating means, the Propagation from the correlation function of the waveform data cross the first ultrasonic reception signal and the second ultrasonic receiving signal It is characterized in that a time difference is obtained.
本発明によれば、強度差算出手段と、乗算値算出手段と、比較手段とを設けることにより、超音波流量計の流量精度の健全性を簡単な構成で判定することができる。 According to the present invention, by providing the intensity difference calculation means, the multiplication value calculation means, and the comparison means, the soundness of the flow accuracy of the ultrasonic flowmeter can be determined with a simple configuration.
また、本発明では、振幅差算出手段と、乗算値算出手段と、比較手段とを設けることにより、超音波流量計の流量精度の健全性を簡単な構成で判定することができる。 Further, in the present invention, by providing the amplitude difference calculating means, the multiplication value calculating means, and the comparing means, the soundness of the flow rate accuracy of the ultrasonic flowmeter can be determined with a simple configuration.
[発明の原理]
発明者は、超音波流量計で計測される上流→下流、下流→上流の超音波受信信号の強度の差に着目した。これにより、特許文献3に開示された超音波流量計よりも簡単に、計測に悪影響があるノイズについて検出可能になる。
図1(A)、図1(B)は本発明の原理を説明する図であり、超音波受信信号にノイズが重畳していない状態を説明する断面図である。図1(A)は配管1の横断面図、図1(B)は図1(A)の配管1の縦断面図である。
[Principle of the invention]
The inventor paid attention to the difference in the intensity of the upstream-to-downstream, downstream-to-upstream ultrasonic reception signals measured by the ultrasonic flowmeter. This makes it possible to more easily detect noise that has an adverse effect on measurement than the ultrasonic flow meter disclosed in Patent Document 3.
1A and 1B are diagrams illustrating the principle of the present invention, and are cross-sectional views illustrating a state in which noise is not superimposed on an ultrasonic reception signal. 1A is a cross-sectional view of the pipe 1, and FIG. 1B is a vertical cross-sectional view of the pipe 1 of FIG.
本発明では、1対の超音波センサ3,4を、配管1の円形断面の円周上の位置が同じで、かつ流体2の流れる方向の位置が異なる箇所に配置する構成とするため、超音波の送受信の伝播経路は図1に示すように配管1の内壁で反射させたV字型の伝播路となる。すなわち、上流側の超音波センサ3は、流体2を介して対向する側の配管1の内壁に向けて超音波信号を送信すると同時に、下流側の超音波センサ4は、流体2を介して対向する側の配管1の内壁に向けて超音波信号を送信する。超音波センサ3が超音波信号を送出する方向と配管1の内壁との成す角、および超音波センサ4が超音波信号を送出する方向と配管1の内壁との成す角は、いずれもθである。 In the present invention, since the pair of ultrasonic sensors 3 and 4 are arranged at locations where the positions on the circumference of the circular cross section of the pipe 1 are the same and the positions in the direction in which the fluid 2 flows are different, The propagation path of the transmission and reception of the sound wave is a V-shaped propagation path reflected on the inner wall of the pipe 1 as shown in FIG. That is, the upstream ultrasonic sensor 3 transmits an ultrasonic signal toward the inner wall of the pipe 1 on the opposite side via the fluid 2, and at the same time, the downstream ultrasonic sensor 4 transmits the ultrasonic signal via the fluid 2. An ultrasonic signal is transmitted toward the inner wall of the pipe 1 on the side to be cleaned. The angle between the direction in which the ultrasonic sensor 3 sends out the ultrasonic signal and the inner wall of the pipe 1 and the angle between the direction in which the ultrasonic sensor 4 sends out the ultrasonic signal and the inner wall of the pipe 1 are θ. is there.
超音波センサ3から送出され超音波センサ4で受信する超音波受信信号Su→dと超音波センサ4から送出され超音波センサ3で受信する超音波受信信号Sd→uとは、流体2の流速Vに比例した位相差(時間差)を持って出力される(時間軸との受信波形との交点であるゼロクロス点も時間差を持つ)。 The ultrasonic reception signal S u → d transmitted from the ultrasonic sensor 3 and received by the ultrasonic sensor 4 and the ultrasonic reception signal S d → u transmitted from the ultrasonic sensor 4 and received by the ultrasonic sensor 3 are the fluid 2 Is output with a phase difference (time difference) proportional to the flow velocity V (the zero-cross point which is the intersection with the time axis and the received waveform also has a time difference).
例えば流速Vが0[m/s]の場合、超音波受信信号Su→dと超音波受信信号Sd→uとの時間差は0[ns]で、位相差も0[rad]である(図2(A))。流速Vが0.3[m/s]の場合、時間差は15[ns]で、位相差は0.12[rad]である(図2(B))。流速Vが3[m/s]の場合、時間差は150[ns]で、位相差は1.22[rad]である(図2(C))。流速Vが6[m/s]の場合、時間差は300[ns]で、位相差は2.45[rad]である(図2(D))。 For example, when the flow velocity V is 0 [m / s], the time difference between the ultrasonic reception signal S u → d and the ultrasonic reception signal S d → u is 0 [ns], and the phase difference is 0 [rad] ( FIG. 2 (A)). When the flow velocity V is 0.3 [m / s], the time difference is 15 [ns] and the phase difference is 0.12 [rad] (FIG. 2B). When the flow velocity V is 3 [m / s], the time difference is 150 [ns], and the phase difference is 1.22 [rad] (FIG. 2C). When the flow velocity V is 6 [m / s], the time difference is 300 [ns] and the phase difference is 2.45 [rad] (FIG. 2 (D)).
一方、超音波を送受信する際に、正規の経路とは違う場所から意図しない同周波数のノイズ(例えば配管1を伝わるノイズ)が混入することがある。このようなノイズが混入すると、超音波受信信号Su→d,Sd→uとノイズとを重ね合わせた波形が観測される。図3(A)は流体の流れがないときに超音波受信信号Su→d,Sd→uに対して位相0°のノイズNが重畳する様子を説明する図、図3(B)は同じく流体の流れがないときに超音波受信信号Su→d,Sd→uに対して位相180°のノイズNが重畳する様子を説明する図である。 On the other hand, when transmitting and receiving ultrasonic waves, unintended noise of the same frequency (for example, noise transmitted through the pipe 1) may be mixed from a place different from the normal path. When such noise is mixed, a waveform in which the ultrasonic reception signals S u → d and S d → u and the noise are superimposed is observed. FIG. 3A is a diagram for explaining how the noise N having a phase of 0 ° is superimposed on the ultrasonic reception signals S u → d and S d → u when there is no fluid flow, and FIG. FIG. 8 is a diagram illustrating a state in which noise N having a phase of 180 ° is superimposed on the ultrasonic reception signals S u → d and S d → u when there is no fluid flow.
図3(A)、図3(B)の例では、ノイズNの位相は水温等の影響を受けず(いつも同じ場所に出現する)、またノイズNは超音波の周波数(例1.3MHz)と同程度の周波数と仮定している。なお、本発明では、流体の流れがないときの超音波受信信号Su→d,Sd→uの位相を基準(0°)とし、この位相に対してノイズNの位相を規定している。 In the example of FIGS. 3A and 3B, the phase of the noise N is not affected by the water temperature or the like (it always appears at the same place), and the noise N is the frequency of the ultrasonic wave (eg, 1.3 MHz). It is assumed that the frequency is about the same as. In the present invention, the phase of the ultrasonic reception signals S u → d and S d → u when there is no fluid flow is set as a reference (0 °), and the phase of the noise N is defined with respect to this phase. .
超音波受信信号Su→d,Sd→uにノイズNが重畳すると、超音波受信信号Su→d,Sd→uの強度が変化するが、上記のとおり流速Vが0[m/s]の状態では超音波受信信号Su→dと超音波受信信号Sd→uの時間差は0[ns]なので、超音波受信信号Su→dの強度と超音波受信信号Sd→uの強度が同様に変化し、強度に差は生じない。すなわち、相関法で算出される伝搬時間差Δtは0であり、ゼロクロス法で算出される伝搬時間t1とt2は等しくなり、流量誤差は生じない。 Ultrasonic wave reception signal S u → d, the noise N is superimposed on S d → u, ultrasonic reception signal S u → d, but the strength of the S d → u changes, above as the flow velocity V is 0 [m / In the state of [s], since the time difference between the ultrasonic reception signal S u → d and the ultrasonic reception signal S d → u is 0 [ns], the intensity of the ultrasonic reception signal S u → d and the ultrasonic reception signal S d → u Similarly changes, and there is no difference in intensity. That is, the propagation time difference Δt calculated by the correlation method is 0, the propagation times t 1 and t 2 calculated by the zero-cross method become equal, and no flow rate error occurs.
しかし、流体の流れがあるときには、超音波受信信号Su→dと超音波受信信号Sd→uには図2(A)〜図2(D)に示したようにずれ(時間差)が生じる。図4(A)は流体の流れがあるときに超音波受信信号Su→d,Sd→uに対して位相0°のノイズNが重畳する様子を説明する図、図4(B)は同じく流体の流れがあるときに超音波受信信号Su→d,Sd→uに対して位相180°のノイズNが重畳する様子を説明する図である。上記と同様に、図4(A)、図4(B)の例では、ノイズNの位相は水温等の影響を受けず、ノイズNは超音波の周波数(例1.3MHz)と同程度の周波数と仮定している。 However, when there is a flow of fluid, there is a difference (time difference) between the ultrasonic reception signals S u → d and the ultrasonic reception signals S d → u as shown in FIGS. 2 (A) to 2 (D). . FIG. 4A is a view for explaining a state in which noise N having a phase of 0 ° is superimposed on the ultrasonic reception signals S u → d and S d → u when there is a fluid flow, and FIG. FIG. 11 is a diagram illustrating a state in which noise N having a phase of 180 ° is superimposed on the ultrasonic reception signals S u → d and S d → u when there is a flow of a fluid. 4A and 4B, the phase of the noise N is not affected by the water temperature or the like, and the noise N is substantially equal to the frequency of the ultrasonic wave (eg, 1.3 MHz). Assume frequency.
流体の流れがあると、超音波センサ3から超音波センサ4(上流→下流)への超音波受信信号Su→dと超音波センサ4から超音波センサ3(下流→上流)への超音波受信信号Sd→uの到達位置が変化するので、超音波受信信号Su→d,Sd→uに対してノイズNが異なる位相で加算される。このため、超音波受信信号Su→dの振幅Yu→dと超音波受信信号Sd→uの振幅Yd→uが異なる変化を示し、信号強度に差が生じる。すなわち、相関法で算出される伝搬時間差Δtとゼロクロス法で算出される伝搬時間t1,t2に誤差が生じる。 When there is a flow of the fluid, the ultrasonic reception signal S u → d from the ultrasonic sensor 3 to the ultrasonic sensor 4 (upstream → downstream) and the ultrasonic wave from the ultrasonic sensor 4 to the ultrasonic sensor 3 (downstream → upstream) Since the arrival position of the reception signal S d → u changes, the noise N is added to the ultrasonic reception signals S u → d and S d → u at different phases. Therefore, shows the change in amplitude Y d → u amplitude Y u → d and ultrasonic reception signal S d → u ultrasonic reception signals S u → d are different, a difference in signal strength occurs. That is, an error occurs between the propagation time difference Δt calculated by the correlation method and the propagation times t 1 and t 2 calculated by the zero-cross method.
次に、超音波受信信号とノイズの位相差による流量誤差を計算する。ここでは、図5(A)に示すような周波数1.3MHzの超音波受信信号Su→d,Sd→uに、図5(B)に示すような同周波数のノイズN(位相は0°〜359°)を足し合わせると、信号強度差と流量誤差とがどうなるのかについて計算した。具体的には、ノイズNによる超音波受信信号Su→d,Sd→uのゼロクロス点の変化について計算した。なお、図5(B)のN0,N90,N180,N270は超音波受信信号Su→d,Sd→uに対してそれぞれ位相が0°,90°,180°,270°ずれたノイズNの波形を示している。 Next, a flow rate error due to a phase difference between the ultrasonic reception signal and noise is calculated. Here, the same frequency noise N (phase is 0) as shown in FIG. 5B is added to the ultrasonic reception signals S u → d and S d → u having a frequency of 1.3 MHz as shown in FIG. (° to 359 °), the signal intensity difference and the flow rate error were calculated. Specifically, the change in the zero-cross point of the ultrasonic reception signals S u → d and S d → u due to the noise N was calculated. The phases of N 0 , N 90 , N 180 , and N 270 in FIG. 5B are 0 °, 90 °, 180 °, and 270 ° with respect to the ultrasonic reception signals Su → d and Sd → u , respectively. The waveform of the shifted noise N is shown.
ノイズNが混入しない場合の超音波受信信号Su→d,Sd→uは、ノイズNが混入しないときの超音波信号の振幅をAS、超音波信号の周波数をf[Hz]、角速度をω[rad/s]、順方向と逆方向の超音波信号の伝搬時間差をΔt[ns]とすると、式(7)、式(8)のように表すことができる。周知のとおり、角速度ωは2πfと等しい。
Su→d=ASsinωt ・・・(7)
Sd→u=ASsin(ωt+Δt) ・・・(8)
When the noise N is not mixed, the ultrasonic reception signals S u → d and S d → u are as follows : when the noise N is not mixed, the amplitude of the ultrasonic signal is A S ; the frequency of the ultrasonic signal is f [Hz]; Is represented by ω [rad / s], and the propagation time difference between the ultrasonic signals in the forward direction and the reverse direction is represented by Δt [ns], which can be expressed as Expressions (7) and (8). As is well known, the angular velocity ω is equal to 2πf.
S u → d = A S sinωt ··· (7)
S d → u = A S sin (ωt + Δt) ··· (8)
また、ノイズNが混入した場合の超音波受信信号Su→d,Sd→uは、ノイズNの振幅をAN、ノイズNの位相差をφ[°]とすると、式(9)、式(10)のように表すことができる。
Su→d=ASsinωt+ANsin(ωt+φ) ・・・(9)
Sd→u=ASsin(ω(t+Δt))+ANsin(ωt+φ) ・・・(10)
Also, the ultrasonic reception signals S u → d and S d → u when the noise N is mixed are expressed by the following equation (9), where A N is the amplitude of the noise N and φ is the phase difference of the noise N. It can be expressed as in equation (10).
S u → d = A S sinωt + A N sin (ωt + φ) ··· (9)
S d → u = A S sin (ω (t + Δt)) + A N sin (ωt + φ) ··· (10)
図6はノイズNが混入した超音波受信信号Su→d,Sd→uの波形を式(9)、式(10)を基に計算した結果を示す図、図7は図6の60の部分を拡大した図、図8は図6の61の部分を拡大した図である。図7〜図8において、Su→d0,Su→d90,Su→d180,Su→d270はそれぞれ超音波受信信号Su→dに位相0°,90°,180°,270°のノイズNが混入したときの波形を示し、Sd→u0,Sd→u90,Sd→u180,Sd→u270はそれぞれ超音波受信信号Sd→uに位相0°,90°,180°,270°のノイズNが混入したときの波形を示している。 FIG. 6 is a view showing the results of calculating the waveforms of the ultrasonic reception signals S u → d and S d → u mixed with the noise N based on the equations (9) and (10), and FIG. FIG. 8 is an enlarged view of a portion 61 in FIG. 7 and 8, Su → d0 , Su → d90 , Su → d180 , and Su → d270 have phases of 0 °, 90 °, 180 °, and 270 ° in the ultrasonic reception signal Su → d , respectively. shows the waveform when the noise N is mixed, S d → u0, S d → u90, S d → u180, S d → u270 each phase 0 ° to the ultrasonic reception signal S d → u, 90 °, 180 ° , 270 ° when noise N is mixed.
図7〜図8によれば、超音波受信信号Su→d,Sd→uに位相差がついたノイズNが加わると、超音波受信信号Su→d,Sd→uのずれが大きくなり、超音波受信信号Su→d,Sd→uの強度に大きな差が生じることが分かる。上記のとおり、強度差が生じることで誤差が発生する。 According to FIGS. 7-8, an ultrasonic reception signal S u → d, S d → the noise N phase difference with is applied to the u, ultrasonic reception signal S u → d, the displacement of S d → u It can be seen that the intensity of the ultrasonic reception signals S u → d and S d → u has a large difference. As described above, an error occurs due to the difference in intensity.
図9、図10に、ノイズNの位相と、流量誤差および超音波受信信号Su→d,Sd→uの強度差との関係を計算した結果を示す。ここでは、ノイズNが混入する場合としない場合の流量Qを相関法を用いて計算して流量誤差を求めている。図9は伝搬時間差Δtが80[ns]で、ノイズNが混入しないときの信号強度の最大値が25000、ノイズNの強度の最大値が500の場合の結果を示し、図10は伝搬時間差Δtが40[ns]で、ノイズNが混入しないときの信号強度の最大値が25000、ノイズNの強度の最大値が500の場合の結果を示しており、図中の100は流量誤差、101は強度差を示している。 9 and 10 show the results of calculating the relationship between the phase of the noise N, the flow rate error, and the intensity difference between the ultrasonic reception signals S u → d and S d → u . Here, the flow rate Q with and without the noise N is calculated using the correlation method to determine the flow rate error. FIG. 9 shows the result when the propagation time difference Δt is 80 [ns], the maximum value of the signal intensity when noise N is not mixed is 25000, and the maximum value of the noise N intensity is 500. FIG. Is 40 [ns], the maximum value of the signal intensity when the noise N is not mixed is 25000, and the maximum value of the intensity of the noise N is 500. In FIG. The intensity difference is shown.
図9、図10に示した計算結果から、ノイズNの大きさと、超音波受信信号Su→d,Sd→uの強度差V’はほぼ比例関係にあり、また強度差V’と流量誤差もほぼ比例関係にあることが分かる。さらに、伝搬時間差Δtおよび強度差V’と流量誤差Eも次式のような比例関係にある。
E[%]∝Δt×|V’| ・・・(11)
From the calculation results shown in FIG. 9 and FIG. 10, the magnitude of the noise N and the intensity difference V ′ between the ultrasonic reception signals S u → d and S d → u are almost proportional to each other. It can be seen that the errors are also approximately proportional. Further, the propagation time difference Δt, the intensity difference V ′, and the flow rate error E also have a proportional relationship as in the following equation.
E [%] ∝Δt × | V ′ | (11)
なお、超音波受信信号Su→dの強度の最大値をYMaxu→d、超音波受信信号Sd→uの強度の最大値をYMaxd→uとすれば、これら最大値の差である強度差V’の絶対値は式(12)のようになる。
|V’|=|YMaxu→d−YMaxd→u| ・・・(12)
If the maximum value of the intensity of the ultrasonic reception signal S u → d is Y Maxu → d and the maximum value of the intensity of the ultrasonic reception signal S d → u is Y Maxd → u , the difference between these maximum values is obtained. The absolute value of the intensity difference V ′ is as shown in Expression (12).
| V '| = | Y Maxu → d −Y Maxd → u | (12)
なお、超音波受信信号Su→dの強度の最小値をYMINu→d、超音波受信信号Sd→uの強度の最小値をYMINd→uとすれば、これら最小値の差である強度差V’の絶対値は式(13)のようになる。
|V’|=|YMINu→d−YMINd→u| ・・・(13)
If the minimum value of the intensity of the ultrasonic reception signal S u → d is Y MINu → d and the minimum value of the intensity of the ultrasonic reception signal S d → u is Y MINd → u , the difference between these minimum values is obtained. The absolute value of the intensity difference V ′ is as shown in Expression (13).
| V '| = | Y MINu → d −Y MINd → u | (13)
式(11)によれば、超音波受信信号Su→d,Sd→uの強度差V’を観察することで流量誤差Eが推定できることが分かる。したがって、流量誤差Eがノイズの影響で大きいと疑われるときは、警報を発して超音波流量計の健全性を保つことが可能となる。 According to equation (11), it can be seen that the flow rate error E can be estimated by observing the intensity difference V ′ between the ultrasonic reception signals S u → d and S d → u . Therefore, when it is suspected that the flow rate error E is large due to the influence of noise, it is possible to issue an alarm and maintain the soundness of the ultrasonic flow meter.
[第1の実施の形態]
以下、本発明の実施の形態について図面を参照して説明する。図11は本発明の第1の実施の形態に係る超音波流量計の構成を示すブロック図である。本実施の形態の超音波流量計は、測定対象の流体2(水等の液体)が流れる配管1と、配管1に取り付けられた超音波センサ3,4と、送信部6と、受信部7と、流量測定部8と、判定部9と、出力部10とを備えている。判定部9は、強度差算出部90と、乗算値算出部91と、比較部92とから構成される。
[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 11 is a block diagram showing the configuration of the ultrasonic flowmeter according to the first embodiment of the present invention. The ultrasonic flowmeter according to the present embodiment includes a pipe 1 through which a fluid 2 (a liquid such as water) to be measured, ultrasonic sensors 3 and 4 attached to the pipe 1, a transmitting unit 6, and a receiving unit 7 , A flow measuring unit 8, a determining unit 9, and an output unit 10. The determination unit 9 includes an intensity difference calculation unit 90, a multiplication value calculation unit 91, and a comparison unit 92.
超音波センサ3,4の配置と超音波信号の伝搬経路については図1(A)、図1(B)で説明したとおりである。送信部6は、超音波センサ3,4に対して駆動用の送信パルスを供給する。これにより、超音波センサ3,4は、送信部6からの送信パルスに応じて、配管1内を流れる流体2に対して斜め方向に超音波信号を送信する。 The arrangement of the ultrasonic sensors 3 and 4 and the propagation path of the ultrasonic signal are as described with reference to FIGS. 1A and 1B. The transmission unit 6 supplies a transmission pulse for driving to the ultrasonic sensors 3 and 4. Accordingly, the ultrasonic sensors 3 and 4 transmit ultrasonic signals in a diagonal direction to the fluid 2 flowing in the pipe 1 in accordance with the transmission pulse from the transmission unit 6.
超音波センサ4は、超音波センサ3から送出された超音波信号の反射信号を受信し、超音波センサ3は、超音波センサ4から送出された超音波信号の反射信号を受信する。
受信部7は、それぞれ超音波センサ3,4で得られた超音波受信信号Su→d,Sd→uに対して増幅等の処理を行う。
The ultrasonic sensor 4 receives a reflected signal of the ultrasonic signal transmitted from the ultrasonic sensor 3, and the ultrasonic sensor 3 receives a reflected signal of the ultrasonic signal transmitted from the ultrasonic sensor 4.
The receiving unit 7 performs processing such as amplification on the ultrasonic reception signals S u → d and S d → u obtained by the ultrasonic sensors 3 and 4, respectively.
流量測定部8は、受信部7から出力された超音波受信信号Su→d,Sd→uを基に、流体2の流速Vおよび流量Qを算出する。流速Vおよび流量Qの算出方法としては、ゼロクロス法(例えば特許文献1参照)、相関法(例えば特許文献2参照)があるが、周知の技術であるので、詳細な説明は省略する。 The flow measurement unit 8 calculates the flow velocity V and the flow rate Q of the fluid 2 based on the ultrasonic reception signals S u → d and S d → u output from the reception unit 7. As a method of calculating the flow velocity V and the flow rate Q, there are a zero-cross method (for example, see Patent Literature 1) and a correlation method (for example, see Patent Literature 2).
図12は本実施の形態の超音波流量計における流量精度の健全性判定処理を説明するフローチャートである。
判定部9の強度差算出部90は、受信部7から出力された超音波受信信号Su→dの最大値YMaxu→dを取得すると共に(図12ステップS1)、受信部7から出力された超音波受信信号Sd→uの最大値YMaxd→uを取得し(図12ステップS2)、強度差V’の絶対値|V’|を式(12)により算出する(図12ステップS3)。
FIG. 12 is a flowchart illustrating a flow rate accuracy soundness determination process in the ultrasonic flowmeter according to the present embodiment.
The intensity difference calculation unit 90 of the determination unit 9 acquires the maximum value Y Maxu → d of the ultrasonic reception signals S u → d output from the reception unit 7 (Step S1 in FIG. 12), and outputs the maximum value Y Maxu → d from the reception unit 7. The maximum value Y Maxd → u of the received ultrasonic reception signals S d → u is obtained (step S2 in FIG. 12), and the absolute value | V ′ | of the intensity difference V ′ is calculated by equation (12) (step S3 in FIG. 12). ).
判定部9の乗算値算出部91は、強度差算出部90が算出した強度差V’の絶対値|V’|と伝搬時間差Δtとの乗算値Δt×|V’|を算出する(図12ステップS4)。伝搬時間差Δtは、超音波受信信号Su→dと超音波受信信号Sd→uのそれぞれをサンプリングして、サンプリングした超音波受信信号Su→dの波形データと超音波受信信号Sd→uの波形データとの相互相関演算を行い、相関関数から伝搬時間差Δtを算出すればよい。このような伝搬時間差Δtの求め方は特許文献2に開示されている。 The multiplication value calculation unit 91 of the determination unit 9 calculates a multiplication value Δt × | V ′ | of the absolute value | V ′ | of the intensity difference V ′ calculated by the intensity difference calculation unit 90 and the propagation time difference Δt (FIG. 12). Step S4). The propagation time difference Δt is obtained by sampling each of the ultrasonic reception signals S u → d and the ultrasonic reception signals S d → u , and obtaining the waveform data of the sampled ultrasonic reception signals S u → d and the ultrasonic reception signals S d → The cross-correlation calculation with the waveform data of u may be performed, and the propagation time difference Δt may be calculated from the correlation function. A method for obtaining such a propagation time difference Δt is disclosed in Patent Document 2.
判定部9の比較部92は、乗算値算出部91が算出した乗算値Δt×|V’|と所定の許容強度差Vaとを比較する(図12ステップS5)。比較部92は、乗算値Δt×|V’|が許容強度差Vaより大きい場合、流量精度が健全でないことを示す警報信号を出力する(図12ステップS6)。許容強度差Vaは、S/N(signal-to-noise)比や、流量の許容精度を考慮して予め設定しておけばよい。 The comparing unit 92 of the determining unit 9 compares the multiplied value Δt × | V ′ | calculated by the multiplied value calculating unit 91 with a predetermined allowable intensity difference Va (Step S5 in FIG. 12). When the multiplied value Δt × | V ′ | is larger than the allowable intensity difference Va, the comparing unit 92 outputs an alarm signal indicating that the flow rate accuracy is not sound (step S6 in FIG. 12). The allowable intensity difference Va may be set in advance in consideration of the S / N (signal-to-noise) ratio and the allowable accuracy of the flow rate.
出力部10は、流量測定部8の算出結果と、判定部9の判定結果とを出力する。流量測定部8の算出結果の出力方法としては、例えば出力部10による表示などがあり、また算出結果の情報を外部に送信するようにしてもよい。同様に、比較部92の判定結果の出力方法としては、出力部10による表示や、警報を知らせるランプの点滅あるいは音声出力などがあり、判定結果の情報を外部に送信するようにしてもよい。 The output unit 10 outputs the calculation result of the flow measurement unit 8 and the determination result of the determination unit 9. As a method of outputting the calculation result of the flow rate measuring unit 8, there is, for example, display by the output unit 10, and information of the calculation result may be transmitted to the outside. Similarly, as a method of outputting the determination result of the comparing unit 92, there is a display by the output unit 10, blinking of a lamp for notifying an alarm or sound output, and the information of the determination result may be transmitted to the outside.
以上のように、本実施の形態では、超音波流量計の流量精度の健全性を簡単な構成で判定することができる。特許文献3に開示された超音波流量計では、流体の温度と圧力を取得しなければならない。これに対して、本実施の形態では、順方向と逆方向の超音波受信信号の強度差を利用することにより、流体の温度と圧力を取得しなくても、流量精度の健全性を判定することができる。流体の温度と圧力で超音波受信信号の大きさが変わっても、流量誤差に与える影響は、超音波受信信号の大きさとノイズの大きさの比率によって決まる。 As described above, in the present embodiment, the soundness of the flow rate accuracy of the ultrasonic flowmeter can be determined with a simple configuration. In the ultrasonic flow meter disclosed in Patent Document 3, the temperature and pressure of the fluid must be obtained. On the other hand, in the present embodiment, the soundness of the flow rate accuracy is determined without using the temperature and the pressure of the fluid by using the intensity difference between the ultrasonic reception signals in the forward direction and the reverse direction. be able to. Even if the magnitude of the ultrasonic reception signal changes depending on the temperature and pressure of the fluid, the influence on the flow rate error is determined by the ratio of the magnitude of the ultrasonic reception signal to the magnitude of the noise.
また、特許文献3に開示された超音波流量計では、流体の種類と流体の温度と流体の圧力の様々な組み合わせについて対応する理論増幅率を登録したデータベースを予め作成しておく必要があるが、本実施の形態では、許容強度差Vaを予め設定しておくだけでよく、データベースを不要にすることができる。また、本実施の形態では、強度差V’を計測することで、超音波センサ3,4の劣化または気泡等の計測異常を検知することができる。 Further, in the ultrasonic flow meter disclosed in Patent Document 3, it is necessary to previously create a database in which the theoretical amplification factors corresponding to various combinations of the type of the fluid, the temperature of the fluid, and the pressure of the fluid are registered. In this embodiment, it is only necessary to set the allowable intensity difference Va in advance, and the database can be made unnecessary. Further, in the present embodiment, by measuring the intensity difference V ', it is possible to detect deterioration of the ultrasonic sensors 3 and 4 or measurement abnormality such as bubbles.
なお、上記の例では、強度差V’を超音波受信信号の最大値から求めているが、最小値から求めるようにしてもよい。すなわち、強度差算出部90は、受信部7から出力された超音波受信信号Su→dの最小値YMINu→dを取得すると共に、受信部7から出力された超音波受信信号Sd→uの最小値YMINd→uを取得し、強度差V’の絶対値|V’|を式(13)により算出するようにしてもよい。 In the above example, the intensity difference V ′ is obtained from the maximum value of the ultrasonic reception signal, but may be obtained from the minimum value. That is, the intensity difference calculation unit 90 obtains the minimum value Y MINu → d of the ultrasonic reception signal S u → d output from the reception unit 7 and obtains the ultrasonic reception signal S d → output from the reception unit 7. The minimum value of u , Y MINd → u, may be obtained, and the absolute value | V ′ | of the intensity difference V ′ may be calculated by equation (13).
[第2の実施の形態]
次に、本発明の第2の実施の形態について説明する。図13は本発明の第2の実施の形態に係る超音波流量計の構成を示すブロック図であり、図11と同一の構成には同一の符号を付してある。本実施の形態の超音波流量計は、配管1と、超音波センサ3,4と、送信部6と、受信部7と、流量測定部8と、判定部9aと、出力部10とを備えている。判定部9aは、比較部92と、振幅差算出部93と、乗算値算出部94とから構成される。
[Second embodiment]
Next, a second embodiment of the present invention will be described. FIG. 13 is a block diagram showing a configuration of an ultrasonic flowmeter according to a second embodiment of the present invention, and the same components as those in FIG. 11 are denoted by the same reference numerals. The ultrasonic flow meter according to the present embodiment includes a pipe 1, ultrasonic sensors 3, 4, a transmitting unit 6, a receiving unit 7, a flow measuring unit 8, a determining unit 9a, and an output unit 10. ing. The determination unit 9a includes a comparison unit 92, an amplitude difference calculation unit 93, and a multiplication value calculation unit 94.
超音波センサ3,4と送信部6と受信部7と流量測定部8の動作は第1の実施の形態で説明したとおりである。
図14は本実施の形態の超音波流量計における流量精度の健全性判定処理を説明するフローチャートである。判定部9aの振幅差算出部93は、受信部7から出力された超音波受信信号Su→dの振幅Yu→dを取得すると共に(図14ステップS10)、受信部7から出力された超音波受信信号Sd→uの振幅Yd→uを取得し(図14ステップS11)、振幅差Y’の絶対値|Y’|を算出する(図14ステップS12)。
|Y’|=|Yu→d−Yd→u| ・・・(14)
The operations of the ultrasonic sensors 3 and 4, the transmitting unit 6, the receiving unit 7, and the flow measuring unit 8 are as described in the first embodiment.
FIG. 14 is a flowchart illustrating a flow rate accuracy soundness determination process in the ultrasonic flow meter according to the present embodiment. The amplitude difference calculation unit 93 of the determination unit 9a acquires the amplitude Y u → d of the ultrasonic reception signal S u → d output from the reception unit 7 (Step S10 in FIG. 14) and outputs the amplitude Y u → d from the reception unit 7. The amplitude Y d → u of the ultrasonic reception signal S d → u is obtained (Step S11 in FIG. 14), and the absolute value | Y ′ | of the amplitude difference Y ′ is calculated (Step S12 in FIG. 14).
| Y ′ | = | Y u → d −Y d → u | (14)
判定部9aの乗算値算出部94は、振幅差算出部93が算出した振幅差Y’の絶対値|Y’|と伝搬時間差Δtとの乗算値Δt×|Y’|を算出する(図14ステップS13)。伝搬時間差Δtの求め方は上記のとおりである。 The multiplication value calculation unit 94 of the determination unit 9a calculates a multiplication value Δt × | Y ′ | of the absolute value | Y ′ | of the amplitude difference Y ′ calculated by the amplitude difference calculation unit 93 and the propagation time difference Δt (FIG. 14). Step S13). The method of determining the propagation time difference Δt is as described above.
判定部9aの比較部92は、乗算値算出部94が算出した乗算値Δt×|Y’|と所定の許容振幅差Yaとを比較する(図14ステップS14)。比較部92は、乗算値Δt×|Y’|が許容振幅差Yaより大きい場合、流量精度が健全でないことを示す警報信号を出力する(図14ステップS15)。許容振幅差Yaは、S/N比や、流量の許容精度を考慮して予め設定しておけばよい。 The comparing unit 92 of the determining unit 9a compares the multiplied value Δt × | Y ′ | calculated by the multiplied value calculating unit 94 with a predetermined allowable amplitude difference Ya (Step S14 in FIG. 14). When the multiplied value Δt × | Y ′ | is larger than the allowable amplitude difference Ya, the comparing unit 92 outputs an alarm signal indicating that the flow rate accuracy is not sound (step S15 in FIG. 14). The allowable amplitude difference Ya may be set in advance in consideration of the S / N ratio and the allowable accuracy of the flow rate.
出力部10は、第1の実施の形態と同様に、流量測定部8の算出結果と、判定部9aの判定結果とを出力する。
こうして、本実施の形態では、第1の実施の形態と同様の効果を得ることができる。
The output unit 10 outputs the calculation result of the flow measurement unit 8 and the determination result of the determination unit 9a, as in the first embodiment.
Thus, in the present embodiment, the same effects as in the first embodiment can be obtained.
第1、第2の実施の形態で説明した超音波流量計のうち少なくとも流量測定部8と判定部9,9aとは、CPU(Central Processing Unit)、記憶装置及びインタフェースを備えたコンピュータと、これらのハードウェア資源を制御するプログラムによって実現することができる。CPUは、記憶装置に格納されたプログラムに従って第1、第2の実施の形態で説明した処理を実行する。 At least the flow measurement unit 8 and the determination units 9 and 9a of the ultrasonic flow meters described in the first and second embodiments are a computer having a CPU (Central Processing Unit), a storage device, and an interface. Can be realized by a program that controls the hardware resources. The CPU executes the processing described in the first and second embodiments according to a program stored in the storage device.
本発明は、超音波流量計に適用することができる。 The present invention can be applied to an ultrasonic flowmeter.
1…配管、2…流体、3,4…超音波センサ、6…送信部、7…受信部、8…流量測定部、9,9a…判定部、10…出力部、90…強度差算出部、91,94…乗算値算出部、92…比較部、93…振幅差算出部。 DESCRIPTION OF SYMBOLS 1 ... Piping, 2 ... Fluid, 3, 4 ... Ultrasonic sensor, 6 ... Transmitting part, 7 ... Receiving part, 8 ... Flow rate measuring part, 9, 9a ... Judgment part, 10 ... Output part, 90 ... Intensity difference calculation part , 91, 94: Multiplied value calculation unit, 92: Comparison unit, 93: Amplitude difference calculation unit.
Claims (3)
この配管の上流と下流に配置された1対の超音波センサと、
上流側の前記超音波センサから送出され下流側の前記超音波センサで受信された第1の超音波受信信号の最大値と下流側の前記超音波センサから送出され上流側の前記超音波センサで受信された第2の超音波受信信号の最大値との差の絶対値、または前記第1の超音波受信信号の最小値と前記第2の超音波受信信号の最小値との差の絶対値を算出する強度差算出手段と、
前記第1の超音波受信信号と前記第2の超音波受信信号の伝搬時間差と、前記強度差算出手段が算出した強度差の絶対値との乗算値を算出する乗算値算出手段と、
この乗算値算出手段が算出した乗算値が所定の許容強度差より大きい場合に、警報を出力する比較手段とを備えることを特徴とする超音波流量計。 A pipe through which the fluid to be measured flows,
A pair of ultrasonic sensors arranged upstream and downstream of the pipe,
The maximum value of the first ultrasonic reception signal transmitted from the ultrasonic sensor on the upstream side and received by the ultrasonic sensor on the downstream side and the ultrasonic sensor transmitted from the ultrasonic sensor on the downstream side and the ultrasonic sensor on the upstream side Absolute value of the difference between the maximum value of the received second ultrasonic reception signal and the absolute value of the difference between the minimum value of the first ultrasonic reception signal and the minimum value of the second ultrasonic reception signal Intensity difference calculating means for calculating
Multiplication value calculation means for calculating a multiplication value of a propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and an absolute value of the intensity difference calculated by the intensity difference calculation means;
An ultrasonic flowmeter comprising: a comparing unit that outputs an alarm when the multiplied value calculated by the multiplied value calculating unit is larger than a predetermined allowable intensity difference.
この配管の上流と下流に配置された1対の超音波センサと、
上流側の前記超音波センサから送出され下流側の前記超音波センサで受信された第1の超音波受信信号の振幅と下流側の前記超音波センサから送出され上流側の前記超音波センサで受信された第2の超音波受信信号の振幅との差の絶対値を算出する振幅差算出手段と、
前記第1の超音波受信信号と前記第2の超音波受信信号の伝搬時間差と、前記振幅差算出手段が算出した振幅差の絶対値との乗算値を算出する乗算値算出手段と、
この乗算値算出手段が算出した乗算値が所定の許容振幅差より大きい場合に、警報を出力する比較手段とを備えることを特徴とする超音波流量計。 A pipe through which the fluid to be measured flows,
A pair of ultrasonic sensors arranged upstream and downstream of the pipe,
The amplitude of the first ultrasonic reception signal transmitted from the ultrasonic sensor on the upstream side and received by the ultrasonic sensor on the downstream side and received by the ultrasonic sensor on the upstream side transmitted from the ultrasonic sensor on the downstream side Amplitude difference calculating means for calculating an absolute value of a difference from the amplitude of the second received ultrasonic signal;
Multiplication value calculation means for calculating a multiplication value of the propagation time difference between the first ultrasonic reception signal and the second ultrasonic reception signal, and the absolute value of the amplitude difference calculated by the amplitude difference calculation means;
An ultrasonic flowmeter comprising: a comparison unit that outputs an alarm when the multiplication value calculated by the multiplication value calculation unit is larger than a predetermined allowable amplitude difference.
前記乗算値算出手段は、前記第1の超音波受信信号および前記第2の超音波受信信号の波形データ相互の相関関数から前記伝搬時間差を求めることを特徴とする超音波流量計。 The ultrasonic flowmeter according to claim 1 or 2,
The multiplication value calculation unit, ultrasonic flowmeter, characterized in that determining the Propagation time difference from the correlation function of the waveform data cross the first ultrasonic reception signal and the second ultrasonic receiving signal.
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