JPH0749978B2 - Electromagnetic flow meter - Google Patents

Electromagnetic flow meter

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Publication number
JPH0749978B2
JPH0749978B2 JP12286488A JP12286488A JPH0749978B2 JP H0749978 B2 JPH0749978 B2 JP H0749978B2 JP 12286488 A JP12286488 A JP 12286488A JP 12286488 A JP12286488 A JP 12286488A JP H0749978 B2 JPH0749978 B2 JP H0749978B2
Authority
JP
Japan
Prior art keywords
converter
flow rate
circuit
output
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
JP12286488A
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Japanese (ja)
Other versions
JPH01292215A (en
Inventor
隆弘 筆保
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shimadzu Corp
Original Assignee
Shimadzu Corp
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Filing date
Publication date
Application filed by Shimadzu Corp filed Critical Shimadzu Corp
Priority to JP12286488A priority Critical patent/JPH0749978B2/en
Publication of JPH01292215A publication Critical patent/JPH01292215A/en
Publication of JPH0749978B2 publication Critical patent/JPH0749978B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Description

【発明の詳細な説明】 (イ)産業上の利用分野 この発明は電磁流量計、特にA/D変換器を備える電磁流
量計に関する。
The present invention relates to an electromagnetic flow meter, and more particularly to an electromagnetic flow meter including an A / D converter.

(ロ)従来の技術 従来の電磁流量計には、第3図に示すものがある。この
電磁流量計は、流体管1の内壁面に露出して一対の電極
2a、2bが対面して設けられる一方、流体管1の軸方向及
び電極2a、2bを結ぶ方向のいずれにも垂直となる方向に
磁界が印加されるように励磁コイル3が配置されてい
る。励磁コイル3には、励磁回路4より、抵抗Rを介し
て低周波パルス状の励磁電流が流される。すなわち、制
御演算部(CPU)8からのスイッチ制御信号により、励
磁回路4のスイッチS1、S2と、スイッチS3、S4が交互に
オン・オフされ、定電流源13からの電流が正負反転され
て励磁コイル3に流れる(第4図のa、励磁電流参
照)。流体管1に水・下水・薬品等の導電性を有する液
体が流れていると、電極2a、2b間に電磁誘導作用によ
り、流量に応じた誘導電圧が発生する(第4図のb、電
極間の発生電圧参照)。この誘導電圧が、バッファアン
プ5a、5bを経て、差動アンプ6で差動増幅され、A/D変
換器7でデジタル信号に変換されて制御演算部8に取り
込まれる。また、励磁電流は抵抗Rで電圧信号に変換さ
れ、アンプ9を経て、A/D変換器10でデジタル信号に変
換され、制御演算部8に取り込まれる。A/D変換器7、1
0のサンプリング動作は、第4図のcで示すように励磁
電流の安定するタイミングに行われる。制御演算部8
は、これらの入力に基づいて流量を計算する。この計算
結果、つまり流量はD/A変換器11でアナログ信号に変換
され、出力回路12より4〜20mAの信号に変換されて出力
される。
(B) Conventional Technology As a conventional electromagnetic flowmeter, there is one shown in FIG. This electromagnetic flowmeter is exposed on the inner wall surface of the fluid pipe 1 and has a pair of electrodes.
While 2a and 2b are provided facing each other, an exciting coil 3 is arranged so that a magnetic field is applied in a direction perpendicular to both the axial direction of the fluid tube 1 and the direction connecting the electrodes 2a and 2b. A low-frequency pulsed exciting current is supplied to the exciting coil 3 from the exciting circuit 4 via the resistor R. That is, the switches S 1 and S 2 and the switches S 3 and S 4 of the excitation circuit 4 are alternately turned on / off by the switch control signal from the control calculation unit (CPU) 8, and the current from the constant current source 13 is supplied. It is inverted in polarity and flows into the exciting coil 3 (see a, exciting current in FIG. 4). When a conductive liquid such as water, sewage, chemicals, etc. is flowing in the fluid pipe 1, an induction voltage corresponding to the flow rate is generated by the electromagnetic induction action between the electrodes 2a and 2b (b in FIG. 4, electrode). Refer to the voltage generated between). The induced voltage is differentially amplified by the differential amplifier 6 through the buffer amplifiers 5a and 5b, converted into a digital signal by the A / D converter 7, and taken into the control calculation unit 8. The exciting current is converted into a voltage signal by the resistor R, passed through the amplifier 9, converted into a digital signal by the A / D converter 10, and taken into the control calculation unit 8. A / D converter 7, 1
The sampling operation of 0 is performed at the timing when the exciting current stabilizes as shown by c in FIG. Control calculation unit 8
Calculates the flow rate based on these inputs. The calculation result, that is, the flow rate is converted into an analog signal by the D / A converter 11 and converted into a signal of 4 to 20 mA by the output circuit 12 and output.

今、例えば、正方向に励磁した時の電極2a、2bに発生し
た電圧をE1、励磁電流をI1とし、負方向に励磁した時の
発生電圧、励磁電流をE2、I2とする。そして、A/D変換
器7の変換係数をK1、A/D変換器10の変換係数をK2とす
ると、流量Qは、 Q=(K1*E1−K1*E2)/(K2*I1−K2*I2) =(K1/K2)*(E1−E2)/(I1−I2) となる。通常は、K1=K2なので、 Q=(E1−E2)/(I1−I2) で表され、この流量Qが演算制御部8で算出する。発生
電圧を同時に測定した励磁電流の値で割算することで定
電流源13のドリフトの影響を取り除くことができる。ま
た、K1*E1−K1*E2のように差を取っているので、A/D
変換器のゼロ点の影響を除去できる。
Now, for example, the voltage generated in the electrodes 2a and 2b when excited in the positive direction is E 1 , the excitation current is I 1, and the generated voltage and the excitation current when excited in the negative direction are E 2 and I 2 . . When the conversion coefficient of the A / D converter 7 is K 1 and the conversion coefficient of the A / D converter 10 is K 2 , the flow rate Q is Q = (K 1 * E 1 −K 1 * E 2 ) / (K 2 * I 1 -K 2 * I 2) = (K 1 / K 2) * a (E 1 -E 2) / ( I 1 -I 2). Normally, K 1 = K 2, so that Q = (E 1 −E 2 ) / (I 1 −I 2 ), and this flow rate Q is calculated by the arithmetic control unit 8. The influence of the drift of the constant current source 13 can be removed by dividing the generated voltage by the value of the exciting current measured at the same time. Also, since the difference is taken as K 1 * E 1 −K 1 * E 2 , the A / D
The effect of the zero point of the converter can be eliminated.

(ハ)発明が解決しようとする課題 上記従来の電磁流量計において、A/D変換器に注目する
と、上記演算式からも明らかなように、A/D変換器のス
パンの性能は、測定全体の精度に直接影響する。例え
ば、温度変化について考えると、これらのA/D変換器の
スパンの温度特性は性能に直結する。そのため、従来は
精度を確保するため、温度特性の優れたA/D変換器を使
用せざるを得ず、しかも、そのA/D変換器1を2個必要
とするため、非常にコスト高となっていた。また、他の
方法として、温度特性の優れた基準電圧を用意し、周期
的に、この電圧をA/D変換器に与えA/D変換器の温度変化
を補償する方法もあるが、こうした基準電圧源もやはり
高価であり、コスト高から、やはり問題があった。
(C) Problems to be Solved by the Invention In the above conventional electromagnetic flowmeter, when attention is paid to the A / D converter, the span performance of the A / D converter is measured as a whole as shown in the above equation. Directly affects the accuracy of. For example, considering the temperature change, the temperature characteristic of the span of these A / D converters is directly related to the performance. Therefore, conventionally, in order to ensure accuracy, it is unavoidable to use an A / D converter with excellent temperature characteristics, and since two A / D converters 1 are required, the cost is extremely high. Was becoming. Another method is to prepare a reference voltage with excellent temperature characteristics and periodically apply this voltage to the A / D converter to compensate for temperature changes in the A / D converter. The voltage source was also expensive, and there was a problem because of the high cost.

この発明は、上記問題点に着目してなされたものであっ
ても、安価なA/D変換器を用いても、温度特性等に優
れ、高精度を得る電磁流量計を提供することを目的とし
ている。
The present invention has been made in view of the above problems, even if using an inexpensive A / D converter, excellent temperature characteristics, etc., to provide an electromagnetic flow meter to obtain high accuracy I am trying.

(ニ)課題を解決するための手段及び作用 この発明の電磁流量計は、流体管の内壁に露出し、互い
に対面して設けられる一対の電極と、前記流体管の軸方
向及び電極方向に直交する方向に磁界を印加する励磁コ
イルと、この励磁コイルに低周波の周期電流を流す励磁
回路と、前記励磁コイルに流れる励磁電流を検出する励
磁電流検出回路と、前記一対の電極間に誘起する流量に
応じた信号電圧を出力する流量信号導出回路と、この流
量信号導出回路からの流量信号をデジタル信号に変換す
る第1のA/D変換器と、前記励磁電流検出回路の出力を
デジタル信号に変換する第2のA/D変換器と、これら第
1及び第2のA/D変換器からの信号を受けて流量を算出
する演算手段とを備えるものにおいて、前記流量信号導
出回路と前記励磁電流検出回路の出力を、前記第1のA/
D変換器と第2のA/D変換器に切替えて接続する切替回路
を備えるとともに、前記演算手段は、前記流量信号導出
回路の出力が第1のA/D変換器に接続され、前記励磁電
流検出回路の出力が第2のA/D変換器に接続される場合
と、前記流量信号導出回路の出力が第2のA/D変換器に
接続され、前記励磁電流検出回路の出力が第1のA/D変
換器に接続される場合のそれぞれに流量を算出する手段
と、算出された両流量の積を算出する積演算手段と、算
出された積を開平し、その開平結果を流量信号として出
力する開平演算手段とを含む構成としている。
(D) Means and Actions for Solving the Problems An electromagnetic flowmeter of the present invention is a pair of electrodes that are exposed on the inner wall of a fluid pipe and face each other, and are orthogonal to the axial direction and the electrode direction of the fluid pipe. An exciting coil for applying a magnetic field in the direction of excitation, an exciting circuit for supplying a low-frequency periodic current to the exciting coil, an exciting current detecting circuit for detecting an exciting current flowing in the exciting coil, and an induction between the pair of electrodes. A flow rate signal derivation circuit that outputs a signal voltage according to the flow rate, a first A / D converter that converts the flow rate signal from the flow rate signal derivation circuit into a digital signal, and the output of the excitation current detection circuit is a digital signal. A flow rate signal deriving circuit and a second A / D converter for converting into a flow rate and a calculation means for calculating a flow rate by receiving signals from the first and second A / D converters. Excitation current detection circuit output Is the first A /
A switching circuit for switching and connecting to the D converter and the second A / D converter is provided, and the arithmetic means has the output of the flow rate signal deriving circuit connected to the first A / D converter, When the output of the current detection circuit is connected to the second A / D converter, and when the output of the flow rate signal derivation circuit is connected to the second A / D converter, the output of the excitation current detection circuit is A unit for calculating the flow rate when connected to one A / D converter, a product calculating unit for calculating the product of both calculated flow rates, and a square root of the calculated product, and the square root result is the flow rate. It is configured to include a square root calculating means for outputting as a signal.

この電磁流量計で、流量を測定する場合、切替回路によ
り、先ず、流量信号導出回路の出力を第1のA/D変換器
に接続し、励磁電流検出回路の出力を第2のA/D変換器
に接続する。この接続状態で、第1及び第2のA/D変換
器の出力に基づいて、演算手段で流量を算出する。次
に、切替回路を動作させて、流量信号導出回路の出力を
第2のA/D変換器に接続し、励磁電流検出回路の出力を
第1のA/D変換器に接続し、この接続状態で第2のA/D変
換器から出力される流量に応じた電圧信号と第1のA/D
変換器から出力される励磁電流に応じた電圧信号とによ
り流量を演算手段で算出する。そして、それぞれ算出さ
れた流量の積を求め、この積を開平して、流量信号を得
る。以上の処理過程で、第1及び第2のA/D変換器の変
換係数K1、K2は流量Qの算出式から除去され、したがっ
て、流量QはA/D変換器の変換係数K1、K2に依存せず、
温度変化の影響を受けない。
When measuring the flow rate with this electromagnetic flow meter, the output of the flow rate signal derivation circuit is first connected to the first A / D converter by the switching circuit, and the output of the excitation current detection circuit is connected to the second A / D converter. Connect to the converter. In this connected state, the flow rate is calculated by the calculation means based on the outputs of the first and second A / D converters. Next, operate the switching circuit, connect the output of the flow rate signal derivation circuit to the second A / D converter, connect the output of the excitation current detection circuit to the first A / D converter, and connect this In the state, the voltage signal according to the flow rate output from the second A / D converter and the first A / D
The flow rate is calculated by the calculation means based on the voltage signal corresponding to the exciting current output from the converter. Then, the product of the respective calculated flow rates is obtained, and the product is squared to obtain the flow rate signal. In the above process, the conversion factors K 1 and K 2 of the first and second A / D converters are removed from the calculation formula of the flow rate Q, so that the flow rate Q is the conversion coefficient K 1 of the A / D converter. , K 2 independent,
Not affected by temperature changes.

(ホ)実施例 以下、実施例により、この発明をさらに詳細に説明す
る。
(E) Examples Hereinafter, the present invention will be described in more detail with reference to Examples.

第1図は、この発明の一実施例を示す電磁流量計のブロ
ック図である。この実施例電磁流量計は、第3図に示す
ものと同様に、流体管1の内壁面に露出して、一対の電
極2a、2bが対面して設けられている。また、流体管1の
軸方向及び電極2a、2bを結ぶ方向のいずれも垂直となる
方向に磁界が印加されるように励磁コイル3が配置され
ている。さらに、励磁コイル3に励磁電流を流す励磁回
路4、電極2a、2b間に発生する電圧を増幅するバッファ
アンプ5a、5b及び差動アンプ6、励磁電流検出用の抵抗
R、この抵抗Rの両端に得られた、励磁電流に対応する
電圧を増幅するアンプ9、2個のA/D変換器7、10、流
量を算出する演算制御部(マイクロコンピュータで構成
される)8、算出された流量をアナログ値に変換するD/
A変換器11、このD/A変換器11の出力を、さらに4〜20mA
の電流に変換して出力する出力回路12を備えている。
FIG. 1 is a block diagram of an electromagnetic flowmeter showing an embodiment of the present invention. The electromagnetic flowmeter of this embodiment is provided with a pair of electrodes 2a and 2b facing each other, which is exposed on the inner wall surface of the fluid pipe 1 like the one shown in FIG. Further, the exciting coil 3 is arranged so that the magnetic field is applied in a direction in which both the axial direction of the fluid pipe 1 and the direction connecting the electrodes 2a and 2b are vertical. Further, an exciting circuit 4 for supplying an exciting current to the exciting coil 3, buffer amplifiers 5a, 5b for amplifying a voltage generated between the electrodes 2a, 2b and a differential amplifier 6, a resistor R for detecting an exciting current, and both ends of this resistor R. The amplifier 9 that amplifies the voltage corresponding to the excitation current, the two A / D converters 7 and 10, the arithmetic control unit (composed of a microcomputer) 8 that calculates the flow rate, the calculated flow rate To an analog value D /
The output of A converter 11 and this D / A converter 11 is 4 to 20 mA.
The output circuit 12 converts the current into a current and outputs the current.

この実施例電磁流量計の特徴は、切替回路14により、差
動アンプ6の出力とアンプ9の出力をそれぞれ切替え
て、A/D変換器7とA/D変換器10に交互接続するようにし
たことである。
The electromagnetic flowmeter of this embodiment is characterized in that the output of the differential amplifier 6 and the output of the amplifier 9 are switched by the switching circuit 14 so that they are alternately connected to the A / D converter 7 and the A / D converter 10. That is what I did.

切替回路14は、スイッチS5、S6、S7、S8からなり、差動
アンプ6の出力端が、スイッチS5、S7の一端に、さらに
アンプ9の出力端がスイッチS6、S8の一端にそれぞれ接
続され、また、スイッチS5、S6の他端がA/D変換器7の
入力端に、さらにスイッチS7、S8の他端がA/D変換器10
の入力端に接続されている。
The switching circuit 14 includes switches S 5 , S 6 , S 7 , and S 8. The output terminal of the differential amplifier 6 is connected to one end of the switches S 5 and S 7 , and the output terminal of the amplifier 9 is connected to the switch S 6 , Each of the switches S 5 and S 6 is connected to one end of S 8 , the other ends of the switches S 5 and S 6 are connected to the input end of the A / D converter 7 , and the other ends of the switches S 7 and S 8 are connected to the A / D converter 10 respectively.
Is connected to the input end of.

演算制御部8は、励磁回路4のスイッチS1乃至S4を切替
えて、励磁電流を発生させる機能を有する他、A/D変換
器7、10にサンプリング信号A、Bを供給する機能、さ
らに、切替回路14にスイッチS5乃至S8をオン/オフする
切替信号を供給する機能、また、切替回路14の切替えに
より、A/D変換器7を介して入力される流量信号と、A/D
変換器10を介して入力される励磁電流により流量を算出
する機能、さらに、逆にA/D変換器10を介して入力され
る流量信号と、A/D変換器7を介して入力される励磁電
流とにより流量を算出する機能、上記2回の流量の積を
求める機能、さらに、この求めた積を開平して、流量を
算出する機能をそれぞれ備えている。
The arithmetic control unit 8 has a function of switching the switches S 1 to S 4 of the exciting circuit 4 to generate an exciting current, and a function of supplying the sampling signals A and B to the A / D converters 7 and 10, and , function of supplying a switching signal to turn on / off the switch S 5 to S 8 to the switching circuit 14, also, by the switching of the switching circuit 14, and a flow rate signal input through the a / D converter 7, a / D
A function of calculating the flow rate by the exciting current input through the converter 10, and conversely, a flow rate signal input through the A / D converter 10 and the flow rate signal input through the A / D converter 7. It has a function of calculating the flow rate by the exciting current, a function of calculating the product of the above two flow rates, and a function of calculating the flow rate by square rooting the calculated product.

次に、この実施例電磁流量計の全体動作について説明す
る。
Next, the overall operation of the electromagnetic flowmeter of this embodiment will be described.

先ず、演算制御部8より、励磁回路4のスイッチS1、S2
とS3、S4を交互に切替えて、励磁回路4より、励磁コイ
ル3及び抵抗Rの直列回路に、第2図aに示す励磁電流
を流す。この励磁電流により、流体管1に交互磁界が印
加され、これにより、流体管1に流れる液体の流量に応
じた電圧が電極2a、2b間に電磁誘導によって発生される
(第2図bの波形参照)。この発生電圧がバッファアン
プ5a、5b及び差動アンプ6を介して出力される。一方、
励磁コイル3に流れる電流に応じた電圧が抵抗Rの両端
より導出され、これがアンプ9を介して出力される。切
替回路14のスイッチS5とS8が演算制御部8からのスイッ
チ切替信号(第2図のe参照)によりオンされ、これに
より差動アンプ6の出力は、A/D変換器7の入力端に接
続される。アンプ9の出力端は、A/D変換器10の入力端
に接続される。演算制御部8からのスイッチS5とS8のオ
ン切替信号に同期して、A/D変換器7とA/D変換器10にそ
れぞれサンプリング信号A(第2図のc参照)が与えら
れ、それぞれ差動アンプ6の出力及びアンプ9の出力、
つまり流量信号と励磁電流が、A/D変換器7及び10を介
して、演算制御部8に取り込まれる。演算制御部8で
は、これら入力された流量信号と励磁電流により流量を
算出する。
First, the arithmetic control unit 8 causes the switches S 1 and S 2 of the excitation circuit 4 to operate.
And S 3 and S 4 are alternately switched, and the exciting current shown in FIG. 2 a is flown from the exciting circuit 4 to the series circuit of the exciting coil 3 and the resistor R. An alternating magnetic field is applied to the fluid pipe 1 by this exciting current, whereby a voltage corresponding to the flow rate of the liquid flowing in the fluid pipe 1 is generated between the electrodes 2a and 2b by electromagnetic induction (waveform in FIG. 2b). reference). This generated voltage is output via the buffer amplifiers 5a and 5b and the differential amplifier 6. on the other hand,
A voltage corresponding to the current flowing through the exciting coil 3 is derived from both ends of the resistor R and is output via the amplifier 9. The switches S 5 and S 8 of the switching circuit 14 are turned on by the switch switching signal (see e in FIG. 2) from the arithmetic control unit 8, whereby the output of the differential amplifier 6 is input to the A / D converter 7. Connected to the end. The output terminal of the amplifier 9 is connected to the input terminal of the A / D converter 10. In synchronization with the switch-on signal of the switch S 5 and S 8 from the operation control unit 8, the A / D converter 7 and the A / D converter 10 to each sampling signal A (see c in FIG. 2) is given , The output of the differential amplifier 6 and the output of the amplifier 9, respectively,
That is, the flow rate signal and the exciting current are taken into the arithmetic control unit 8 via the A / D converters 7 and 10. The arithmetic control unit 8 calculates the flow rate from the input flow rate signal and the exciting current.

次に、続いて演算制御部8は、切替回路14のスイッチS6
とS7に、これらスイッチをオンするための切替信号(第
2図のf参照)を供給すると同時に、A/D変換器7、10
にもサンプリング信号B(第2図のd参照)を出力す
る。このスイッチS6とS7のオンにより、今度は差動アン
プ6の出力端がA/D変換器10に接続される。アンプ9の
出力端がA/D変換器7の入力端に接続される。その結
果、演算制御部8には、A/D変換器10を経て、流量信号
が取り込まれ、逆にA/D変換器7を経て、励磁電流が取
り込まれる。この流量信号と励磁電流により、同じく流
量が算出される。そして、演算制御部8では、2回に亘
り求めた積を求めるとともに、これを開平演算し、その
開平値を最終結果値の流量Qとして、D/A変換器11でア
ナログ信号に変換し、出力回路12を経て出力する。
Next, subsequently, the arithmetic control unit 8 controls the switch S 6 of the switching circuit 14.
And S 7 are supplied with switching signals (see f in FIG. 2) for turning on these switches, and at the same time, A / D converters 7 and 10 are connected.
Also, the sampling signal B (see d in FIG. 2) is output. When the switches S 6 and S 7 are turned on, the output terminal of the differential amplifier 6 is connected to the A / D converter 10 this time. The output end of the amplifier 9 is connected to the input end of the A / D converter 7. As a result, the flow rate signal is taken in through the A / D converter 10 and the exciting current is taken in through the A / D converter 7 in the arithmetic control unit 8. The flow rate is similarly calculated from the flow rate signal and the exciting current. Then, the arithmetic control unit 8 obtains the product obtained twice and performs square root calculation, and the square root value is used as the flow rate Q of the final result value and converted into an analog signal by the D / A converter 11, Output through the output circuit 12.

上記切替回路14とA/D変換器7、A/D変換器10及び演算制
御部8の動作に関し、第1のサンプリング信号Aが入力
された第1のタイミングのA/D変換器7より演算制御部
8に入力される信号は、K1*E1であり、A/D変換器10か
ら取り込まれる信号は、K2*I2となる。これに対し、サ
ンプリング信号Bが入力される第2のタイミングで演算
制御部8に取り込まれる信号は、A/D変換器7よりK2*E
2となり、A/D変換器10よりK1*I1となる。
Regarding the operations of the switching circuit 14, the A / D converter 7, the A / D converter 10 and the operation control unit 8, the operation is performed by the A / D converter 7 at the first timing when the first sampling signal A is input. The signal input to the control unit 8 is K 1 * E 1 , and the signal fetched from the A / D converter 10 is K 2 * I 2 . On the other hand, the signal taken into the arithmetic control unit 8 at the second timing when the sampling signal B is input is K 2 * E from the A / D converter 7.
2 and K 1 * I 1 from A / D converter 10.

ここで、第1のタイミングにおける流量Q1は、 となり、第2回目の流量Q2は、 となる。Here, the flow rate Q 1 at the first timing is And the second flow rate Q 2 is Becomes

制御演算部8では、このQ1、Q2の積を求め、 この式より明らかなように、A/D変換器7、及び10の係
数K1とK2は消去された形となり、その結果、出力される
流量Qは、A/D変換器7、10の変換係数K1、K2の影響を
受けず、温度変化等の影響を受けない、極めて特性の良
い計測を行うことができる。すなわち、温度が変化し、
変換係数がK1からK1′、K2からK2′に変化しても、演算
結果Qには何ら影響を与えなく、変化の影響を受けない
ことになる。また、当然のことではあるが、K1*E1−K1
*K2といったような形でそれぞれの差をとっているの
で、ゼロ点の影響を従来例と同様に除去し得る。
The control calculation unit 8 obtains the product of these Q 1 and Q 2 , As is clear from this equation, the coefficients K 1 and K 2 of the A / D converters 7 and 10 are eliminated, and as a result, the output flow rate Q is the same as that of the A / D converters 7 and 10. It is possible to perform measurement with extremely good characteristics that is not affected by the conversion coefficients K 1 and K 2 and is not affected by temperature changes and the like. That is, the temperature changes,
Even if the conversion coefficient changes from K 1 to K 1 ′ or from K 2 to K 2 ′, the calculation result Q is not affected and is not affected by the change. Also, of course, K 1 * E 1 −K 1
Since each difference is obtained in the form of * K 2 , the effect of the zero point can be eliminated as in the conventional example.

なお、上記実施例では、励磁電流を正負交互に繰返す場
合を例を示したが、この発明は、励磁電流を正・休止・
負・休止・正・…と繰返す場合、あるいは正・休止・正
・休止・…、また、負・休止・負・休止・…と繰返す場
合にも、もちろん適用できる。
In the above embodiment, the case where the exciting current is alternately repeated positively and negatively is shown as an example.
It is of course applicable to the case of repeating negative / pause / positive / ..., or the case of repeating positive / pause / positive / pause / ..., or negative / pause / negative / pause / ....

(ヘ)発明の効果 この発明によれば、流量信号導出回路の出力と、励磁電
流検出回路の出力をそれぞれ第1、第2のA/D変換器に
切替えて接続し、第1、第2のA/D変換器から、それぞ
れ流量信号と励磁電流を切替えて取出し、これらの信号
に基づいて流量を算出し、その流量の算出積を開平し
て、流量を求めるものであるから、各A/D変換器の変換
係数が流量結果から消去されることになり、従って、A/
D変換器の変換係数の影響を何ら受けることなく流量を
検出することができるので、温度変化等の影響を受けな
い、精度の良い流量計測が可能となる。しかも、そのた
め安価なA/D変換器を使用しても差し支えないので、全
体としても安価な電磁流量計を実現できる。
(F) Effect of the Invention According to the present invention, the output of the flow rate signal derivation circuit and the output of the excitation current detection circuit are connected to the first and second A / D converters by switching them respectively. The flow rate signal and exciting current are switched and extracted from the A / D converter of each, the flow rate is calculated based on these signals, and the calculated product of the flow rate is squared to obtain the flow rate. The conversion factor of the / D converter will be removed from the flow rate result and therefore A /
Since the flow rate can be detected without being affected by the conversion coefficient of the D converter, it is possible to measure the flow rate with high accuracy without being affected by temperature changes and the like. In addition, since it is possible to use an inexpensive A / D converter, it is possible to realize an inexpensive electromagnetic flow meter as a whole.

【図面の簡単な説明】[Brief description of drawings]

第1図は、この発明の一実施例を示す電磁流量計のブロ
ック図、第2図は、同電磁流量計の動作を説明するため
の波形タイムチャート、第3図は従来の電磁流量計のブ
ロック図、第4図は、同電磁流量の動作を説明するため
の波形タイムチャートである。 1:流体管、2a・2b:電極、3:励磁コイル、4:励磁回路、5
a・5b:バッファアンプ、6:差動アンプ、7・10:A/D変換
器、8:演算制御部、9:アンプ、R:励磁電流検出用抵抗、
14:切替回路。
FIG. 1 is a block diagram of an electromagnetic flowmeter showing an embodiment of the present invention, FIG. 2 is a waveform time chart for explaining the operation of the electromagnetic flowmeter, and FIG. 3 is a conventional electromagnetic flowmeter. The block diagram and FIG. 4 are waveform time charts for explaining the operation of the same electromagnetic flow rate. 1: Fluid tube, 2a ・ 2b: Electrode, 3: Excitation coil, 4: Excitation circuit, 5
a ・ 5b: Buffer amplifier, 6: Differential amplifier, 7 ・ 10: A / D converter, 8: Arithmetic control unit, 9: Amplifier, R: Excitation current detection resistor,
14: Switching circuit.

Claims (1)

【特許請求の範囲】[Claims] 【請求項1】流体管の内壁に露出し、互いに対面して設
けられる一対の電極と、前記流体管の軸方向及び電極方
向に直交する方向に磁界を印加する励磁コイルと、この
励磁コイルに低周波の周期電流を流す励磁回路と、前記
励磁コイルに流れる励磁電流を検出する励磁電流検出回
路と、前記一対の電極間に誘起する流量に応じた信号電
圧を出力する流量信号導出回路と、この流量信号導出回
路からの流量信号をデジタル信号に変換する第1のA/D
変換器と、前記励磁電流検出回路の出力をデジタル信号
に変換する第2のA/D変換器と、これら第1及び第2のA
/D変換器からの信号を受けて流量を算出する演算手段と
を備える電磁流量計において、 前記流量信号導出回路と前記励磁電流検出回路の出力
を、前記第1のA/D変換器と第2のA/D変換器に切替えて
接続する切替回路を備えるとともに、前記演算手段は、
前記流量信号導出回路の出力が第1のA/D変換器に接続
され、前記励磁電流検出回路の出力が第2のA/D変換器
に接続される場合と、前記流量信号導出回路の出力が第
2のA/D変換器に接続され、前記励磁電流検出回路の出
力が第1のA/D変換器に接続される場合のそれぞれに流
量を算出する手段と、算出された両流量の積を算出する
積演算手段と、算出された積を開平し、その開平結果を
流量信号として出力する開平演算手段とを含むものであ
ることを特徴とする電磁流量計。
1. A pair of electrodes exposed on the inner wall of a fluid pipe and facing each other, an exciting coil for applying a magnetic field in a direction orthogonal to the axial direction and the electrode direction of the fluid pipe, and the exciting coil. An exciting circuit for flowing a low-frequency periodic current, an exciting current detecting circuit for detecting an exciting current flowing through the exciting coil, and a flow rate signal deriving circuit for outputting a signal voltage according to a flow rate induced between the pair of electrodes, The first A / D that converts the flow rate signal from this flow rate signal derivation circuit into a digital signal
A converter, a second A / D converter for converting the output of the exciting current detection circuit into a digital signal, and the first and second A / D converters.
In an electromagnetic flowmeter including a calculation means for calculating a flow rate by receiving a signal from the / D converter, the outputs of the flow rate signal derivation circuit and the exciting current detection circuit are supplied to the first A / D converter and the A switching circuit for switching and connecting to two A / D converters is provided, and the arithmetic means is
The output of the flow rate signal derivation circuit is connected to the first A / D converter, the output of the exciting current detection circuit is connected to the second A / D converter, and the output of the flow rate signal derivation circuit Is connected to the second A / D converter, and the output of the exciting current detection circuit is connected to the first A / D converter. An electromagnetic flowmeter comprising: a product calculating means for calculating a product; and a square root calculating means for square rooting the calculated product and outputting the square root result as a flow rate signal.
JP12286488A 1988-05-19 1988-05-19 Electromagnetic flow meter Expired - Lifetime JPH0749978B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP12286488A JPH0749978B2 (en) 1988-05-19 1988-05-19 Electromagnetic flow meter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP12286488A JPH0749978B2 (en) 1988-05-19 1988-05-19 Electromagnetic flow meter

Publications (2)

Publication Number Publication Date
JPH01292215A JPH01292215A (en) 1989-11-24
JPH0749978B2 true JPH0749978B2 (en) 1995-05-31

Family

ID=14846524

Family Applications (1)

Application Number Title Priority Date Filing Date
JP12286488A Expired - Lifetime JPH0749978B2 (en) 1988-05-19 1988-05-19 Electromagnetic flow meter

Country Status (1)

Country Link
JP (1) JPH0749978B2 (en)

Also Published As

Publication number Publication date
JPH01292215A (en) 1989-11-24

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