JP4069521B2

JP4069521B2 - Flow measuring device

Info

Publication number: JP4069521B2
Application number: JP28242798A
Authority: JP
Inventors: 修江口; 行夫長岡; 晃一竹村
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1998-10-05
Filing date: 1998-10-05
Publication date: 2008-04-02
Anticipated expiration: 2018-10-05
Also published as: JP2000111369A

Description

【０００１】
【発明の属する技術分野】
本発明はガスなどの流量を計測する流量計測装置に関するものである。
【０００２】
【従来の技術】
従来のこの種の流量計測装置は図８に示すように流体管路１の一部に熱式のフローセンサのような流量検出手段２を備え、制御手段７の信号によって流量計測を開始し、その出力信号を信号処理手段１０で増幅あるいはデジタル化し、流量算出手段により流量を算出する。このように電子的に流量を計測する際、流路を流れる実際の流量がゼロでも信号処理手段１０を構成する電子部品の様々な要因（特性、バラツキ等）により、その流量算出結果がある値（オフセット量）を示すことがある。
【０００３】
この値は本来の流量値に上乗せされて出力され、その値自体が誤差となり流量計測の精度を低下させる。そのため、これを補正し精度を確保するために一般に流路の上流側に設けられる流路開閉手段を閉じて流路の流量をゼロにして計測した流量測定値を、以後（流路開閉手段を開に戻した状態）の流量測定値からキャンセルしていた。
【０００４】
そして、このような流量ゼロ時の流量計測（ゼロ点補正量計測）を一定時間毎または、一定積算流量に達する毎に行っていた。
【０００５】
【発明が解決しようとする課題】
しかしながら、例えば家庭用のガス消費量を計量するガスメーターでは、流路開閉手段は一般に流路の上流側に設けられ、流路開閉手段を閉じても近くでガスエンジンが運転されると圧力変動により流量がゼロにはならない。このような状態で流量を計測しても圧力変動による流量を計測するため、流路開閉手段を開状態に戻した後の流量計測値からこの流量測定値をキャンセルしても前述の回路のオフセット量をキャンセルできず、むしろ測定精度を低下させる原因となる。
【０００６】
また、流体中に超音波を送信又は受信する送受信器の間の超音波の伝搬時間より流量を検出する流量測定装置に於いて、超音波の受信波の電圧レベルが変動している不安定な状態に、ゼロ点の補正量の計測を行うと上記の場合と同様に以降の流量測定精度を低下させる可能性がある。
【０００７】
従って、ゼロ点補正量の計測を正しく行い測定精度を向上させるには、上記のようなゼロ点補正量の計測に適さない状態を認識し、正しくゼロ点補正量の計測が行える状態の時のみ、補正量の計測を行うことが課題となっていた。
【０００８】
【課題を解決するための手段】
本発明は上記課題を解決するため、流路を開閉する流路開閉手段と、流体中に設けられ超音波信号を送信または受信する第１送受信器及び第２送受信器と、前記第１送受信器から前記第２送受信器に送信する第１送信モードと前記第２送受信器から前記第１送受信器に送信する第２送信モードを変更する切換手段と、受信波形を所定の電圧に増幅する増幅手段と、増幅後の受信波形と基準信号とを比較する比較手段と、前記増幅手段の増幅度の変化を監視する増幅監視手段と、前記第１送信モード及び前記第２送信モードのそれぞれの伝搬時間を計測する計時手段と、前記計時手段のそれぞれの計時値の差に基づいて流量を検出する流量検出手段と、前記流路開閉手段が閉時の前記流量検出手段の測定値を記憶する誤差記憶手段と、前記流量検出手段の測定値と前記誤差記憶手段の記憶値とから流量を補正する流量補正手段と、前記増幅度監視部、前記流量検出手段からの入力により前記流路開閉手段の制御と前記流量検出手段の計測を開始させる制御手段とからなり、前記増幅手段で受信信号のピーク電圧を所定の電圧に増幅した際の増幅度が変化した旨を前記増幅監視手段により検知した際に、前記誤差記憶手段の更新を行わないようにしたものであり、以降の流量測定において回路のオフセット量をキャンセル出来、流量計測の精度を向上することが出来る。
【０００９】
【発明の実施の形態】
本発明の流量計測装置は、流路を開閉する流路開閉手段と、流体中に設けられ超音波信号を送信または受信する第１送受信器及び第２送受信器と、前記第１送受信器から前記第２送受信器に送信する第１送信モードと前記第２送受信器から前記第１送受信器に送信する第２送信モードを変更する切換手段と、受信波形を所定の電圧に増幅する増幅手段と、増幅後の受信波形と基準信号とを比較する比較手段と、前記増幅手段の増幅度の変化を監視する増幅監視手段と、前記第１送信モード及び前記第２送信モードのそれぞれの伝搬時間を計測する計時手段と、前記計時手段のそれぞれの計時値の差に基づいて流量を検出する流量検出手段と、前記流路開閉手段が閉時の前記流量検出手段の測定値を記憶する誤差記憶手段と、前記流量検出手段の測定値と前記誤差記憶手段の記憶値とから流量を補正する流量補正手段と、前記増幅度監視部、前記流量検出手段からの入力により前記流路開閉手段の制御と前記流量検出手段の計測を開始させる制御手段とからなり、前記増幅手段で受信信号のピーク電圧を所定の電圧に増幅した際の増幅度が変化した旨を前記増幅監視手段により検知した際に、前記誤差記憶手段の更新を行わないようにしたもので、流量の変化、圧力または温度の変化により増幅手段の増幅度が変化した時にオフセット量の測定を行い、誤ったオフセット量を以降の流量計測の補正に用いることを防ぐことが出来、流量計測の精度を確保することが出来る。
【００１０】
【実施例】
以下、本発明の実施例について図面を用いて説明する。
【００１１】
（実施例１）
図１は本発明の実施例１の流量計測装置を示すブロック図である。
【００１２】
図１において、流路８の流れの中に、例えば発熱体の温度変化によって流量を検出する熱式フローセンサのような流量検出部２を配置する。制御手段７の信号によって流量検出部２を加熱させ、流量検出部２の出力信号を信号処理手段１０で増幅、フィルタ、あるいはＡ／Ｄコンバータでデジタル化する。この信号処理手段１０の信号は流量算出手段４で流路８の大きさや流量サンプリングの時間などを考慮して流量値に変換される。前記流量検出部２、信号処理手段１０、流量算出手段４とで流量検出手段２１を構成している。流路８内の流れが安定している場合、すなわち大きく変動していない状態では、低消費電力化をはかるため流量サンプリングは数秒間に1回行われている。この状態で制御手段７により一定時間経過または一定の積算流量を測定する毎に、流路開閉手段１を閉じて、その時の流量算出手段４の値を流量ゼロ時のオフセット量として誤差記憶手段５に記憶して、流量補正手段６により以降の流量算出手段４の流量値よりキャンセルする。
【００１３】
しかし流路８内の流れに周期的な変動がある場合には、図２に示すように流量測定値がQ１、Q２、Q３のように変動が生じる。そこで流量検出手段４において流量測定値Q１〜Q３までの変動値が所定レベルより大きく流量変動があると判断したときは、オフセット量算出禁止の信号を制御手段７に出力し、これにより制御手段７では前述の流量ゼロ時の測定タイミングが到来しても、この測定は実行せず誤差記憶手段５の記憶値の更新は行わない。このように、流量オフセットのキャンセルのための流量誤差記憶手段５の記憶値は流量変動の少ないときに限り更新されるものである。それにより、近くでガスエンジンが使用され、流量変動の大きい場合に誤差記憶手段５の記憶値が更新され、それ以降の流量の測定値に影響することはない。
【００１４】
（実施例２）
図３は本発明の実施例２の流量計測装置のブロック図である。実施例１と異なるところは、流量検出手段の測定値の変動に基づいて周期を検出する周期検出手段を設けた点にある。すなわち、図２に示すように流量検出手段の測定値の変動所定レベルより大きい流量変動がある判断した場合には、図４に示すように小さい周期でｔ０〜ｔｎまで流量サンプリングを行う。このサンプリングにより周期検出手段３で周期Ｔを求め、この周期Ｔが所定より大きい値であればオフセット量算出禁止の信号を制御手段７に出力する。制御手段７ではこれにより、実施例１で述べた制御手段７による流量ゼロ時の測定タイミングが到来しても、オフセット量の測定は実行せず、従って誤差記憶手段５の記憶値の更新も行わない。
【００１５】
つまり誤差記憶手段５の記憶値の更新は周期検出手段３よりオフセット量算出禁止信号が出力されていない流量の変動が少ない場合に限られる。こうする事により、流量変動の大きい場合に誤差記憶手段５の記憶値を更新して、それ以降の流量の測定値に影響するということはなくなる。
【００１６】
（実施例３）
図５は本発明の実施例３の流量計測装置のブロック図である。実施例１と異なるところは、流れの変動を直接検出する検出器を設けた点にある。すなわち流路８の流れの中に流量変動検出手段１１を設ける。この流量変動検出手段１１によって周期的な流量の変動を検出し、その変動値がある値を超えた場合には、その旨のオフセット量算出禁止の信号を制御手段７に出力し、制御手段７ではこれにより、実施例１で述べた制御手段７による流量ゼロ時の測定タイミングが到来しても、オフセット量の測定は実行せず、従って誤差記憶手段５の記憶値の更新も行わない。つまり、誤差記憶手段５の記憶値の更新は流量変動検出手段１１よりオフセット量算出禁止信号が出力されていない流量の変動が少ない場合に限られる。こうする事により、流量変動の大きい場合に誤差記憶手段５の記憶値を更新して、それ以降の流量の測定値に影響するということはなくなる。
【００１７】
流量変動検出手段１１として圧力検出器を使用することができる。
【００１８】
圧力検出器は流路８内の圧力を検出し、圧力変動と流量変動の関係をあらかじめ求めておけば流量変動の大きさに換算でき、周期的な圧力変化の大きさが所定レベルを越えたときに、制御手段７にオフセット量測定禁止信号を出力する。
【００１９】
圧力検出器が流体の供給圧力の異常や流路８から外部への漏洩を検出するために設けられている場合には兼用することもできる。また、流量変動検出手段１１は常時流体の変動を監視している必要はなく、流量算出手段４によって周期的な変動がある場合のみ変動を監視すればよい。すなわち、図６に示すように流量算出手段４によって流量が周期的な変動を起こしたと判断されたとき、制御手段７で流量変動検出手段１１を起動して流路を流れる流体の変動を測定する。そして、流量変動検出手段１１により周期的な流量の変動を検出し、その変動値がある値を超えた場合には、その旨のオフセット量算出禁止の信号を制御手段７に出力し、制御手段７では、流量ゼロ時の測定タイミングが到来しても、オフセット量の測定を実行しない。
【００２０】
（実施例４）
図７は本発明の実施例４を示すもので、実施例１と異なるところは流量検出手段として超音波を使用している点にある。すなわち図７において、流路８の途中に超音波を送信する第１送受信器１１と受信する第２送受信器１２が流れ方向に配置されている。１３は第1送受信器１１への送信回路、１４は第2送受信器１２で受信した信号の増幅回路で、この増幅された信号は基準信号と比較回路１５で比較され、基準信号以上の信号が検出されたとき回数設定手段１６で設定された回数だけ繰り返し手段１７で、制御手段７で超音波信号を繰り返し発信する。繰り返しの回数設定手段１６で設定された回数が繰り返されたときの時間をタイマカウンタのような計時手段１８で求める。
【００２１】
次に切操手段１９で第１送受信器１１と第2送受信器１２の送受信を切り換えて、第2送受信器１２から第１送受信器１１すなわち下流から上流に向かって超音波信号を送信し、この送信を前述のように繰り返し、その時間を計時する。そしてその時間差から流路の大きさや流れの状態を考慮して流量算出手段４で流量値を求める。この流量値が周期的に変動している場合にはオフセット量算出禁止の信号を制御手段７に出力し、これにより制御手段７では前述の流量ゼロ時の測定タイミングが到来しても、オフセット量の測定は実行せず、従って誤差記憶手段５の記憶値の更新も行わない。
【００２２】
つまり流量変動検出手段３よりオフセット量測定の可否の信号が出力され、誤差記憶手段５の記憶値の更新は流量変動検出手段３よりオフセット量算出禁止信号が出力されていない流量の変動が少ない場合に限られる。
【００２３】
（実施例５）
図８は本発明の実施例５を示すもので、実施例３と異なるところは増幅手段の増幅度を監視し、制御手段に信号を送出する増幅監視手段を備えた点にある。すなわち図８において、増幅手段１４の増幅度を監視し、増幅度に変化があればその旨を制御手段７に知らせる増幅監視手段２０が設けられている。
【００２４】
図８は増幅手段１４の動作の説明図である。増幅手段１４は第１送受信器１１、及び第２送受信器１２で受信した信号が後段の比較手段１５において正確に比較が行われるように、図のように所定の電圧幅に信号のピーク又は平均値が入るように増幅する。この増幅度は流体の条件、例えば流量、流体の温度、圧力に変化がなければほぼ一定である。増幅監視手段２０では増幅手段１４の増幅度を監視していて、変化があれば制御手段７にその旨の信号を出力する。制御手段７ではこの増幅監視手段２０より増幅度に変化があった旨の信号を入力してから後、一定時間は、流量ゼロ時の測定タイミングが到来しても、この測定を実行せず誤差記憶手段５の記憶値の更新は行わない。誤差記憶手段５の記憶値が更新されないので、誤差記憶手段５の記憶値は前回測定されたオフセット量の測定値のままである。つまり、増幅手段１４の増幅度が何らかの原因で変化した時に、オフセットのキャンセルのための流量ゼロ時の測定を行わないようにするものである。
【００２５】
【発明の効果】
以上の説明から明らかのように本発明に係る流量計測装置は、増幅監視手段により増幅手段の増幅度の変化を検出し、増幅度の変化がある場合にはオフセットキャンセル量の測定を行わないようにしたもので、流量の変化、圧力または温度の変化により増幅手段の増幅度が変化した時にオフセット量の測定を行い、誤ったオフセット量を以降の流量計測の補正に用いることを防ぐことが出来、流量計測の精度を確保できるという効果がある。
【図面の簡単な説明】
【図１】本発明の実施例１における流量計測装置のブロック図
【図２】同装置における流量変動の波形図
【図３】本発明の実施例２における流量計測装置のブロック図
【図４】同装置における周期検出手段の動作を説明する波形図
【図５】本発明の実施例３における流量計測装置のブロック図
【図６】同装置に於いて流量変動検出装置を制御手段により起動する場合を示すブロック図
【図７】本発明の実施例４における流量計測装置のブロック図
【図８】同装置における流量計測装置のブロック図
【図９】従来の流量計測装置のブロック図
【符号の説明】
１流路開閉手段
４流量算出手段
５誤差記憶手段
６流量補正手段
７制御手段
８流路[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate measuring device for measuring a flow rate of gas or the like.
[0002]
[Prior art]
As shown in FIG. 8, this type of conventional flow rate measuring device includes a flow rate detection means 2 such as a thermal flow sensor in a part of the fluid conduit 1, and starts flow rate measurement according to a signal from the control means 7. The output signal is amplified or digitized by the signal processing means 10, and the flow rate is calculated by the flow rate calculation means. Thus, when the flow rate is electronically measured, the flow rate calculation result has a certain value due to various factors (characteristics, variation, etc.) of the electronic components constituting the signal processing means 10 even if the actual flow rate flowing through the flow path is zero. (Offset amount) may be indicated.
[0003]
This value is added to the original flow rate value and output, and the value itself becomes an error, which decreases the accuracy of flow rate measurement. For this reason, in order to correct this and ensure accuracy, the flow rate measurement value measured with the flow rate of the flow channel of the flow channel being zeroed by closing the flow channel opening / closing means generally provided on the upstream side of the flow channel is hereinafter referred to Canceled from the flow rate measurement value in the state of returning to the open state).
[0004]
Then, the flow rate measurement (zero point correction amount measurement) at the time of zero flow rate is performed every certain time or every time when a certain integrated flow rate is reached.
[0005]
[Problems to be solved by the invention]
However, for example, in a gas meter that measures gas consumption for home use, the flow path opening / closing means is generally provided on the upstream side of the flow path, and even if the flow path opening / closing means is closed, if the gas engine is operated nearby, The flow rate does not become zero. Even if the flow rate is measured in such a state, the flow rate due to pressure fluctuation is measured. Therefore, even if this flow rate measurement value is canceled from the flow rate measurement value after the flow path opening / closing means is returned to the open state, the above-described circuit offset The amount cannot be canceled, but rather causes a reduction in measurement accuracy.
[0006]
In addition, in a flow measurement device that detects the flow rate from the propagation time of ultrasonic waves between transmitters and receivers that transmit or receive ultrasonic waves in a fluid, the voltage level of the received waves of ultrasonic waves is unstable. If the correction amount of the zero point is measured in the state, the subsequent flow rate measurement accuracy may be lowered as in the above case.
[0007]
Therefore, in order to correctly measure the zero point correction amount and improve the measurement accuracy, only when the zero point correction amount measurement is recognized and the zero point correction amount measurement can be performed correctly. It has been a problem to measure the correction amount.
[0008]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a channel opening / closing means for opening / closing a channel, a first transmitter / receiver for transmitting or receiving an ultrasonic signal provided in a fluid, and the first transmitter / receiver. Switching means for changing the first transmission mode to be transmitted from the second transceiver to the second transceiver and the second transmission mode to be transmitted from the second transceiver to the first transceiver, and the amplifying means for amplifying the received waveform to a predetermined voltage. A comparison means for comparing the received waveform after amplification with the reference signal, an amplification monitoring means for monitoring a change in the amplification degree of the amplification means, and a propagation time of each of the first transmission mode and the second transmission mode. An error memory for storing a measured value of the flow rate detecting means when the flow path opening / closing means is closed, a flow rate detecting means for detecting a flow rate based on a difference between respective time measured values of the time measuring means, Means and the flow rate Flow rate correction means for correcting the flow rate from the measured value of the output means and the stored value of the error storage means; control of the flow path opening / closing means and input of the flow rate detection means by input from the amplification degree monitoring unit and the flow rate detection means; The error storage means when the amplification monitoring means detects that the degree of amplification has changed when the amplification means amplifies the peak voltage of the received signal to a predetermined voltage. In the subsequent flow rate measurement, the offset amount of the circuit can be canceled and the accuracy of the flow rate measurement can be improved.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Flow rate measurement apparatus of the present invention, the flow channel opening and closing means for opening and closing the flow path, and a first transceiver and a second transceiver for transmitting or receiving ultrasonic signals provided in the fluid, from the first transceiver Switching means for changing a first transmission mode for transmission to the second transceiver and a second transmission mode for transmission from the second transceiver to the first transceiver; and amplifying means for amplifying the received waveform to a predetermined voltage ; A comparison means for comparing the received waveform after amplification with a reference signal, an amplification monitoring means for monitoring a change in the amplification degree of the amplification means, and a propagation time of each of the first transmission mode and the second transmission mode. Time measuring means for measuring, flow rate detecting means for detecting a flow rate based on a difference between respective time measured values of the time measuring means, and error storage means for storing a measured value of the flow rate detecting means when the flow path opening / closing means is closed And the flow rate detecting means Flow rate correction means for correcting the flow rate from the measured value and the stored value of the error storage means, control of the flow path opening and closing means and measurement of the flow rate detection means by input from the amplification degree monitoring unit and the flow rate detection means. The error storage means is updated when the amplification monitoring means detects that the amplification level has changed when the amplification means amplifies the peak voltage of the received signal to a predetermined voltage. The offset amount is measured when the amplification degree of the amplification means changes due to a change in flow rate, a change in pressure or temperature, and the use of an incorrect offset amount for correction of subsequent flow measurement is prevented. It is possible to ensure the accuracy of flow measurement.
[0010]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0011]
Example 1
FIG. 1 is a block diagram showing a flow rate measuring apparatus according to Embodiment 1 of the present invention.
[0012]
In FIG. 1, a flow rate detection unit 2 such as a thermal flow sensor that detects a flow rate according to a temperature change of a heating element is disposed in the flow of the flow path 8. The flow rate detection unit 2 is heated by a signal from the control unit 7, and the output signal of the flow rate detection unit 2 is amplified by the signal processing unit 10, digitized by a filter, or an A / D converter. The signal from the signal processing unit 10 is converted into a flow rate value by the flow rate calculation unit 4 in consideration of the size of the flow path 8 and the flow rate sampling time. The flow rate detector 2, the signal processor 10, and the flow rate calculator 4 constitute a flow rate detector 21. When the flow in the flow path 8 is stable, that is, in a state where it does not fluctuate greatly, the flow rate sampling is performed once every few seconds in order to reduce power consumption. In this state, every time when the control means 7 measures a certain time or a constant integrated flow rate, the flow path opening / closing means 1 is closed, and the value of the flow rate calculation means 4 at that time is used as an offset amount when the flow rate is zero. The flow rate correction means 6 cancels the flow rate value of the flow rate calculation means 4 thereafter.
[0013]
However, when there is a periodic fluctuation in the flow in the flow path 8, the flow rate measurement values fluctuate as shown in Q1, Q2, and Q3 as shown in FIG. Therefore, when the flow rate detection means 4 determines that the fluctuation values of the flow rate measurement values Q1 to Q3 are larger than a predetermined level and there is a flow rate fluctuation, a signal for prohibiting the calculation of the offset amount is output to the control means 7, thereby Then, even when the above-described measurement timing at zero flow rate comes, this measurement is not executed and the stored value in the error storage means 5 is not updated. Thus, the stored value of the flow rate error storage means 5 for canceling the flow rate offset is updated only when the flow rate fluctuation is small. Thereby, when the gas engine is used nearby and the flow rate fluctuation is large, the stored value of the error storage means 5 is updated, and the measured value of the flow rate thereafter is not affected.
[0014]
(Example 2)
FIG. 3 is a block diagram of the flow rate measuring apparatus according to the second embodiment of the present invention. The difference from the first embodiment is that a period detecting means for detecting a period based on a variation in the measured value of the flow rate detecting means is provided. That is, as shown in FIG. 2, when it is determined that there is a flow rate fluctuation greater than a predetermined level, the flow rate sampling is performed from t0 to tn in a small cycle as shown in FIG. By this sampling, the period detection means 3 obtains the period T, and if the period T is a value larger than a predetermined value, an offset amount calculation prohibition signal is output to the control means 7. As a result, the control means 7 does not measure the offset amount even when the measurement timing when the flow rate is zero by the control means 7 described in the first embodiment, and therefore the stored value of the error storage means 5 is also updated. Absent.
[0015]
That is, the update of the stored value of the error storage means 5 is limited to the case where there is little fluctuation in the flow rate when the offset amount calculation prohibition signal is not output from the period detection means 3. By doing so, the stored value of the error storage means 5 is not updated when the flow rate fluctuation is large, and the measured value of the flow rate thereafter is not affected.
[0016]
(Example 3)
FIG. 5 is a block diagram of a flow rate measuring apparatus according to Embodiment 3 of the present invention. The difference from the first embodiment is that a detector for directly detecting flow fluctuations is provided. That is, the flow rate fluctuation detecting means 11 is provided in the flow of the flow path 8. The flow rate fluctuation detecting unit 11 detects a periodic flow rate fluctuation. When the fluctuation value exceeds a certain value, an offset amount calculation prohibition signal to that effect is output to the control unit 7. Thus, even when the measurement timing when the flow rate is zero by the control means 7 described in the first embodiment arrives, the offset amount is not measured, and therefore the stored value of the error storage means 5 is not updated. That is, the update of the stored value of the error storage means 5 is limited to the case where the fluctuation of the flow rate for which the offset amount calculation prohibition signal is not output from the flow rate fluctuation detection means 11 is small. By doing so, the stored value of the error storage means 5 is not updated when the flow rate fluctuation is large, and the measured value of the flow rate thereafter is not affected.
[0017]
A pressure detector can be used as the flow rate fluctuation detecting means 11.
[0018]
The pressure detector detects the pressure in the flow path 8, and if the relationship between the pressure fluctuation and the flow fluctuation is obtained in advance, it can be converted into the magnitude of the flow fluctuation, and the magnitude of the cyclic pressure change exceeds a predetermined level. Sometimes, the control unit 7 outputs an offset amount measurement prohibition signal.
[0019]
If the pressure detector is provided to detect an abnormality in the supply pressure of the fluid or leakage from the flow path 8 to the outside, it can also be used. Further, the flow rate fluctuation detecting means 11 does not need to constantly monitor the fluctuation of the fluid, and the flow rate calculating means 4 only needs to monitor the fluctuation when there is a periodic fluctuation. That is, as shown in FIG. 6, when the flow rate calculation means 4 determines that the flow rate has periodically changed, the control means 7 activates the flow rate fluctuation detection means 11 to measure the fluctuation of the fluid flowing through the flow path. . Then, the flow rate fluctuation detecting means 11 detects a periodic flow rate fluctuation, and when the fluctuation value exceeds a certain value, an offset amount calculation prohibition signal to that effect is output to the control means 7, and the control means In 7, the measurement of the offset amount is not executed even when the measurement timing at the time of zero flow rate comes.
[0020]
Example 4
FIG. 7 shows a fourth embodiment of the present invention. The difference from the first embodiment is that ultrasonic waves are used as the flow rate detecting means. That is, in FIG. 7, the 1st transmitter / receiver 11 which transmits an ultrasonic wave in the middle of the flow path 8, and the 2nd transmitter / receiver 12 which receives are arrange | positioned in the flow direction. Reference numeral 13 denotes a transmission circuit for the first transmitter / receiver 11, and reference numeral 14 denotes an amplifier circuit for the signal received by the second transmitter / receiver 12. The amplified signal is compared with the reference signal by the comparison circuit 15, and a signal higher than the reference signal is obtained. When it is detected, an ultrasonic signal is repeatedly transmitted by the control means 7 by the repeat means 17 by the number of times set by the number setting means 16. The time when the number of times set by the repetition number setting means 16 is repeated is obtained by the time counting means 18 such as a timer counter.
[0021]
Next, the switching means 19 switches between transmission / reception of the first transmitter / receiver 11 and the second transmitter / receiver 12, and transmits an ultrasonic signal from the second transmitter / receiver 12 to the first transmitter / receiver 11, that is, from downstream to upstream, The transmission is repeated as described above, and the time is counted. From the time difference, the flow rate calculation means 4 determines the flow rate value in consideration of the size of the flow path and the flow state. When the flow rate value fluctuates periodically, an offset amount calculation prohibition signal is output to the control means 7, so that the control means 7 can detect the offset amount even when the above-described measurement timing at zero flow rate arrives. Therefore, the stored value of the error storage means 5 is not updated.
[0022]
That is, a signal indicating whether or not the offset amount can be measured is output from the flow rate fluctuation detecting unit 3, and the update of the stored value in the error storage unit 5 is performed when the flow rate fluctuation detecting unit 3 does not output the offset amount calculation prohibition signal and the flow rate fluctuation is small. Limited to.
[0023]
(Example 5)
FIG. 8 shows a fifth embodiment of the present invention, which is different from the third embodiment in that an amplification monitoring means for monitoring the amplification degree of the amplification means and sending a signal to the control means is provided. That is, in FIG. 8, amplification monitoring means 20 is provided for monitoring the amplification degree of the amplification means 14 and notifying the control means 7 if there is a change in the amplification degree.
[0024]
FIG. 8 is an explanatory diagram of the operation of the amplifying means 14. The amplifying means 14 has a signal peak or average within a predetermined voltage width as shown in the figure so that the signals received by the first transmitter / receiver 11 and the second transmitter / receiver 12 are accurately compared in the comparison means 15 in the subsequent stage. Amplify to enter value. This amplification is almost constant if there are no changes in the fluid conditions such as flow rate, fluid temperature, and pressure. The amplification monitoring means 20 monitors the amplification degree of the amplification means 14 and outputs a signal to that effect to the control means 7 if there is a change. The control means 7 does not execute this measurement for a certain period of time after input of a signal indicating that the degree of amplification has changed from the amplification monitoring means 20 even if the measurement timing at a flow rate of zero arrives. The stored value in the storage means 5 is not updated. Since the stored value of the error storage unit 5 is not updated, the stored value of the error storage unit 5 remains the measurement value of the offset amount measured last time. That is, when the amplification degree of the amplifying means 14 is changed for some reason, the measurement at zero flow rate for canceling the offset is not performed.
[0025]
【The invention's effect】
As is apparent from the above description, the flow rate measuring apparatus according to the present invention detects the change in the amplification degree of the amplification means by the amplification monitoring means, and does not measure the offset cancellation amount when there is a change in the amplification degree. Therefore, the offset amount is measured when the amplification degree of the amplification means changes due to a change in flow rate, pressure or temperature, and it is possible to prevent the incorrect offset amount from being used for correction of the subsequent flow measurement. This has the effect of ensuring the accuracy of flow rate measurement.
[Brief description of the drawings]
FIG. 1 is a block diagram of a flow rate measuring device according to a first embodiment of the present invention. FIG. 2 is a waveform diagram of flow rate fluctuations in the same device. FIG. 3 is a block diagram of a flow rate measuring device according to a second embodiment of the present invention. FIG. 5 is a block diagram of a flow rate measuring device according to a third embodiment of the present invention. FIG. 6 shows a case where the flow rate fluctuation detecting device is activated by the control unit in the same device. FIG. 7 is a block diagram of a flow rate measuring device in Embodiment 4 of the present invention. FIG. 8 is a block diagram of a flow rate measuring device in the same device. FIG. 9 is a block diagram of a conventional flow rate measuring device. ]
DESCRIPTION OF SYMBOLS 1 Flow path opening / closing means 4 Flow rate calculation means 5 Error storage means 6 Flow rate correction means 7 Control means 8 Flow path

Claims

A channel opening / closing means for opening and closing the channel, a first transmitter / receiver for transmitting or receiving an ultrasonic signal provided in the fluid, and a first transmitter / receiver for transmitting an ultrasonic signal from the first transmitter / receiver to the second transmitter / receiver. A switching means for changing a first transmission mode and a second transmission mode transmitted from the second transceiver to the first transceiver; an amplifying means for amplifying a received waveform to a predetermined voltage ; an amplified received waveform and a reference signal; Comparing means, amplification monitoring means for monitoring changes in the amplification of the amplification means, timing means for measuring the propagation times of the first transmission mode and the second transmission mode, and the timing means A flow rate detecting means for detecting a flow rate based on a difference between respective time measurement values, an error storage means for storing a measured value of the flow rate detecting means when the flow path opening / closing means is closed, and a measured value of the flow rate detecting means And the error memory A flow rate correction means for correcting the flow rate from the stored value of the amplification degree monitoring unit consists of a control means for starting the measurement of the flow rate detecting means and the control of the flow path opening and closing means by the input from the flow rate detecting unit The flow rate measuring device which does not update the error storage means when the amplification monitoring means detects that the amplification degree when the peak voltage of the received signal is amplified to a predetermined voltage by the amplification means .