JPS6128284B2 - - Google Patents
Info
- Publication number
- JPS6128284B2 JPS6128284B2 JP5152380A JP5152380A JPS6128284B2 JP S6128284 B2 JPS6128284 B2 JP S6128284B2 JP 5152380 A JP5152380 A JP 5152380A JP 5152380 A JP5152380 A JP 5152380A JP S6128284 B2 JPS6128284 B2 JP S6128284B2
- Authority
- JP
- Japan
- Prior art keywords
- excitation
- current
- excitation current
- electrodes
- flow velocity
- 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
Links
- 230000005284 excitation Effects 0.000 claims description 45
- 239000012530 fluid Substances 0.000 claims description 8
- 238000010586 diagram Methods 0.000 description 5
- 238000000034 method Methods 0.000 description 4
- 238000011109 contamination Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000004043 responsiveness Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
- G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
- G01F1/56—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects
- G01F1/58—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using electric or magnetic effects by electromagnetic flowmeters
- G01F1/60—Circuits therefor
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
Description
【発明の詳細な説明】
本発明は、矩形波励磁方式の電磁流量計に関す
るものであつて、低消費電力で作動するこの種の
電磁流量計を実現しようとするものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rectangular wave excitation type electromagnetic flowmeter, and aims to realize this type of electromagnetic flowmeter that operates with low power consumption.
一般に矩形波励磁方式の電磁流量計では、励磁
コイルに電流が流れている期間と、流れていない
期間とが等しくなるように選び、励磁電流が流れ
ているときの信号電圧の定常値と、励磁電流が流
れていないときの信号電圧の定常値をそれぞれサ
ンプルホールドした後、その差から流量に対応し
た信号を検出している。したがつて矩形波励磁方
式の電磁流量計によれば、直流励磁方式で問題と
なる電極間に生ずる電気化学的不平衡電圧の影響
を受けず、また交流励磁方式で問題となる90゜ノ
イズの影響や電極の汚れによるコモンモードノイ
ズの影響を受けない等の特徴がある。その反面、
0.5〜1.0A程度の電流をオンオフして励磁コイル
に与える必要があり、消費電力が大きいうえに、
電流をオンオフするためのスイツチ素子の発熱に
よる信頼性低下や、発熱対策が必要等の欠点があ
る。 Generally, in an electromagnetic flowmeter using a rectangular wave excitation method, the period in which current is flowing through the excitation coil is selected to be equal to the period in which it is not flowing, and the steady value of the signal voltage when the excitation current is flowing is After sampling and holding the steady-state values of the signal voltages when no current is flowing, a signal corresponding to the flow rate is detected from the difference. Therefore, an electromagnetic flowmeter using a rectangular wave excitation method is not affected by electrochemical unbalanced voltage that occurs between electrodes, which is a problem with a DC excitation method, and is free from 90° noise, which is a problem with an AC excitation method. It has features such as being unaffected by common mode noise caused by dirt and electrode contamination. On the other hand,
It is necessary to apply a current of about 0.5 to 1.0A to the excitation coil by turning it on and off, which not only consumes a lot of power, but also
There are drawbacks such as reduced reliability due to heat generated by the switch element for turning the current on and off, and the need to take measures to prevent heat generation.
ここにおいて、本発明は、励磁電流の振幅Iお
よびくり返しを被測定流体の流速に関連して制御
することによつて、従来装置における前記した欠
点を有効に除去し、消費電力の少ない電磁流量計
を実現しようとするものである。 Here, the present invention effectively eliminates the above-described drawbacks of conventional devices by controlling the amplitude I and repetition rate of the excitation current in relation to the flow velocity of the fluid to be measured, and provides an electromagnetic flowmeter with low power consumption. This is what we are trying to achieve.
第1図は本発明にかかわる電磁流量計の一実施
例を示す構成ブロツク図である。図において、1
は矩形波励磁回路で、直流電圧源2、この直流電
圧源2に直列に接続される電流制御回路3、この
電流制御回路に直列に接続されここからの電流I
をオンオフするスイツチ素子4を有している。5
は電磁流量計発信器で、励磁コイル6、被測定流
体が流れるパイプ7および電極81,82を備え
ている。9は電極81,82間に生ずる起電力を
増幅する増幅器、10は増幅器9からの信号を入
力するコントローラで、スイツチ素子4と電流制
御回路3を介して、励磁コイル6に流れる励磁電
流の振幅I及びくり返し周期Tを制御する。11
は演算回路で、励磁コイル6に流れる励磁電流の
振幅I、くり返し周期Tに関連した信号を入力し
ている。 FIG. 1 is a block diagram showing an embodiment of an electromagnetic flowmeter according to the present invention. In the figure, 1
is a rectangular wave excitation circuit, which includes a DC voltage source 2, a current control circuit 3 connected in series to this DC voltage source 2, and a current I connected in series to this current control circuit.
It has a switch element 4 that turns on and off. 5
is an electromagnetic flowmeter transmitter, which includes an excitation coil 6, a pipe 7 through which a fluid to be measured flows, and electrodes 81 and 82. 9 is an amplifier that amplifies the electromotive force generated between the electrodes 81 and 82; 10 is a controller that inputs a signal from the amplifier 9; I and repetition period T are controlled. 11
is an arithmetic circuit which receives signals related to the amplitude I and repetition period T of the excitation current flowing through the excitation coil 6.
このように構成した装置の動作を第2図を参照
しながら次に説明する。 The operation of the apparatus configured as described above will be explained below with reference to FIG.
この装置いおいては、コントローラ10は、増
幅器9を介して印加される電極81,82間に生
ずる起電力に対応した信号、すなわち、励磁電流
が流れていないとき生ずる不平衡電圧と、パイプ
7を流れる被測定流体の流速Vに関連した信号と
を交互に入力しており、被測定流体の流速が低く
なると、すなわち低流速領域では、第2図イに示
すように励磁電流の振幅Iを増大させ、電流を流
している時間(時間幅)tとくり返し周期Tとの
比t/Tが小さくなるように制御する。また、被
測定流体の流速が速くなると、すなわち高流速領
域では、第2図ロに示すように励磁電流の振幅I
を減少させ、電流を流している時間tとくり返し
周期Tとの比t/Tが大きくなるように制御す
る。 In this device, the controller 10 receives a signal corresponding to the electromotive force generated between the electrodes 81 and 82 applied via the amplifier 9, that is, an unbalanced voltage generated when no excitation current is flowing, and a pipe 7. When the flow velocity of the fluid to be measured becomes low, that is, in the low flow velocity region, the amplitude I of the excitation current is changed as shown in Fig. 2A. control is performed so that the ratio t/T of the time (time width) during which the current is flowing and the repetition period T becomes small. Furthermore, as the flow velocity of the fluid to be measured increases, that is, in the high flow velocity region, the amplitude of the exciting current I
is controlled so that the ratio t/T between the current flowing time t and the repetition period T is increased.
発信器5の電極81,82間には、励磁コイル
6に流れる励磁電流Iとパイプ7を流れる被測定
流体の流速Vに応じた起電力eと、不平衡電圧e
Bとの和電圧eSが発生するもので、この関係を(1)
式に示す。 Between the electrodes 81 and 82 of the transmitter 5, there is an electromotive force e corresponding to the excitation current I flowing through the excitation coil 6, the flow velocity V of the fluid to be measured flowing through the pipe 7, and an unbalanced voltage e.
A sum voltage e S with B is generated, and this relationship can be expressed as (1)
As shown in the formula.
eS=K・D・I・V+eB
ただし、K:定数
D:電極81,82間の距離
e=K・D・I・V
コントローラ10は、前記したように増幅器9
からの信号eIに応じて励磁電流の振幅I、くり
返し周期t/Tを制御しており、励磁電流が流れ
ていないとき生ずる電極81,82間の起電力e
B(不平衡電圧)と励磁電流を流したとき生ずる
電極81,82間の起電力eSとの差電圧e(=
eS−eB)が、流速Vにかかわらず常に一定な値
になるように制御する。このように制御すると、
(1)式は(2)式のように表わすことができる。 e S =K・D・I・V+e B However, K: Constant D: Distance between electrodes 81 and 82 e=K・D・I・V As described above, the controller 10 is connected to the amplifier 9
The amplitude I and repetition period t/T of the excitation current are controlled according to the signal e I from the
B (unbalanced voltage) and the difference voltage e (=
e S −e B ) is controlled so that it always has a constant value regardless of the flow velocity V. When controlled like this,
Equation (1) can be expressed as equation (2).
I=e/K・D・1/v
=Ko・1/v (2)
ただしKo=e/K・Dで一定値
(2)式から明らかなように、本発明にかかわる装
置においては、励磁電流の振幅Iは被測定流体の
流速Vと反比例の関係となり、低流速ほど励磁電
流の振幅Iが大きくなり、高流速ほど励磁電流の
振幅Iが小さくなる。 I=e/K・D・1/v =Ko・1/v (2) However, Ko=e/K・D, which is a constant value.As is clear from equation (2), in the device according to the present invention, The amplitude I of the current is inversely proportional to the flow velocity V of the fluid to be measured; the lower the flow velocity, the larger the amplitude I of the excitation current, and the higher the flow velocity, the smaller the amplitude I of the excitation current.
演算回路11は、励磁電流の振幅Iに関連した
信号を入力しており、逆数演算することによつて
流速Vに関連した信号epを得ることができる。 The arithmetic circuit 11 receives a signal related to the amplitude I of the excitation current, and can obtain a signal e p related to the flow velocity V by performing reciprocal calculation.
ここで、直流電源2から供給する時間的に平均
化した励磁電流Iavは、電流幅tを一定とすれば
(3)式で表わされる。 Here, the temporally averaged excitation current Iav supplied from the DC power supply 2 is, if the current width t is constant.
It is expressed by equation (3).
Iav=I・t/T (3)
コントローラ10は、励磁電流のくり返し周期
Tを、(4)式に示すように振幅Iに比例し、すなわ
ち流速Vに反比例して大きく制御するもので、こ
れによつて、平均化した励磁電流Iavは(5)式の通
りとなる。 Iav=I・t/T (3) The controller 10 greatly controls the repetition period T of the excitation current in proportion to the amplitude I, that is, inversely proportional to the flow velocity V, as shown in equation (4). Accordingly, the averaged excitation current Iav is as shown in equation (5).
T=k・I (4)
Iav=t/k=const (5)
(5)式より直流電源2から供給される平均的な電
力は、電流幅tにより決まる一定な値となり、こ
の電流幅を適当に選定することによつて消費電力
を低く維持させることができる。 T=k・I (4) Iav=t/k=const (5) From equation (5), the average power supplied from the DC power supply 2 is a constant value determined by the current width t, and this current width is By making appropriate selections, power consumption can be kept low.
なお、この装置においては、流速v=0で(2)式
から明らかなように励磁電流の振幅Iが無限大に
なるので、一定値以下の低流速では動作を停止す
るようにしている。 In this device, the amplitude I of the excitation current becomes infinite when the flow velocity v=0, as is clear from equation (2), so the operation is stopped at a low flow velocity below a certain value.
この装置によれば、消費電力を低く抑えなが
ら、低流速領域では、励磁電流の振幅Iが大きく
なるので、S/Nを良好にすることができ、ま
た、高流速領域では、励磁電流のくり返し周期T
が小さくなるので応答性を良好にできる。したが
つて、本発明によれば、低容量の電源で効率的に
動作する電磁流量計を実現することができる。 According to this device, while keeping power consumption low, the amplitude I of the excitation current increases in the low flow rate region, making it possible to improve the S/N ratio, and in the high flow rate region, the excitation current is repeatedly Period T
Since this decreases, responsiveness can be improved. Therefore, according to the present invention, it is possible to realize an electromagnetic flowmeter that operates efficiently with a low-capacity power source.
なお、上記の実施例においては励磁電流を第2
図に示すように一方の極性に変化するパルス波形
としたものであるが、第3図あるいは第4図に示
すように、正負両極性に変化するパルス波形とし
てもよい。また、ここではコントローラと演算回
路とを別々のブロツク図で示したが、これらを例
えばサンプルホールド回路とマイクロプロセツサ
で構成する等すれば、両者を共用することもでき
る。また、ここでは励磁電流の振幅値Iを逆数演
算することによつて流速Vに関連した信号を得る
ようにしたが、(4)式からくり返し周期Tと振幅値
Iとは比例関係にあるのでこの周期Tを逆数演算
して流速Vを得るようにしてもよい。 Note that in the above embodiment, the excitation current is
As shown in the figure, the pulse waveform changes to one polarity, but as shown in FIG. 3 or 4, the pulse waveform may change to both positive and negative polarities. Furthermore, although the controller and the arithmetic circuit are shown as separate block diagrams here, they can be used in common if they are constructed of, for example, a sample-and-hold circuit and a microprocessor. In addition, here, the signal related to the flow velocity V was obtained by calculating the reciprocal of the amplitude value I of the excitation current, but from equation (4), the repetition period T and the amplitude value I are in a proportional relationship. The flow velocity V may be obtained by calculating the reciprocal of this period T.
以上説明したように、本発明によれば、低消費
電力で効率的に動作する矩形波励磁方式の電磁流
量計が実現できる。 As described above, according to the present invention, it is possible to realize a rectangular wave excitation type electromagnetic flowmeter that operates efficiently with low power consumption.
第1図は本発明装置の一実施例の構成ブロツク
図、第2図は第1図装置における励磁電流の波形
図、第3図および第4図は、本発明装置に適用可
能な他の励磁電流の波形図である。
1……矩形波励磁回路、2……直流電圧源、3
……電流制御回路、4……スイツチ素子、5……
発信器、6……励磁コイル、7……パイプ、8
1,82……電極、9……増幅器、10……コン
トローラ、11……演算回路。
Fig. 1 is a block diagram of the configuration of one embodiment of the device of the present invention, Fig. 2 is a waveform diagram of the excitation current in the device of Fig. 1, and Figs. It is a waveform diagram of a current. 1... Rectangular wave excitation circuit, 2... DC voltage source, 3
...Current control circuit, 4...Switch element, 5...
Transmitter, 6... Excitation coil, 7... Pipe, 8
1, 82...electrode, 9...amplifier, 10...controller, 11...arithmetic circuit.
Claims (1)
の励磁電流が供給される励磁コイルと、被測定流
体が流れるパイプに設けられた一対の電極とを備
えた電磁流量計において、 前記励磁コイルと直列に接続した電流制御回路
とスイツチ素子、前記一対の電極間に発生する信
号を入力し、励磁電流が流れていないときに電極
間に発生する信号と励磁電流を流したときに電極
間に発生する信号との差が一定値になるように、
前記電流制御回路を介して前記励磁電流の振幅値
Iを制御するとともに、前記スイツチ素子を介し
て所定時間幅の励磁電流を供給しそのくり返し周
期Tを励磁電流の振幅値Iに比例させて制御する
コントローラ、前記励磁電流の振幅値I又は繰返
し周期Tを逆数演算し被測定流体の流速に関連し
た信号を出力する演算回路を設けたことを特徴と
する電磁流量計。[Claims] 1. An electromagnetic flowmeter comprising a rectangular wave excitation circuit, an excitation coil to which excitation current is supplied from the rectangular wave excitation circuit, and a pair of electrodes provided on a pipe through which a fluid to be measured flows. A current control circuit and a switch element connected in series with the excitation coil are input with a signal generated between the pair of electrodes, and a signal generated between the electrodes when no excitation current is flowing and an excitation current are passed. so that the difference between the signal that sometimes occurs between the electrodes is a constant value,
The amplitude value I of the excitation current is controlled through the current control circuit, and the excitation current is supplied with a predetermined time width through the switch element, and the repetition period T is controlled in proportion to the amplitude value I of the excitation current. An electromagnetic flowmeter comprising: a controller that performs a reciprocal operation on the amplitude value I or repetition period T of the excitation current; and an arithmetic circuit that calculates a reciprocal of the amplitude value I or repetition period T of the excitation current and outputs a signal related to the flow velocity of the fluid to be measured.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5152380A JPS56148015A (en) | 1980-04-18 | 1980-04-18 | Electromagnetic flowmeter |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP5152380A JPS56148015A (en) | 1980-04-18 | 1980-04-18 | Electromagnetic flowmeter |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS56148015A JPS56148015A (en) | 1981-11-17 |
JPS6128284B2 true JPS6128284B2 (en) | 1986-06-30 |
Family
ID=12889364
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP5152380A Granted JPS56148015A (en) | 1980-04-18 | 1980-04-18 | Electromagnetic flowmeter |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS56148015A (en) |
Families Citing this family (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60250213A (en) * | 1984-05-28 | 1985-12-10 | Aichi Tokei Denki Co Ltd | Magnetic flowmeter |
US5079957A (en) * | 1989-09-20 | 1992-01-14 | Rosemount Inc. | Conversion circuit for an electromagnetic flow transmitter |
DE102004044606A1 (en) * | 2004-09-13 | 2006-03-30 | Endress + Hauser Flowtec Ag | Device and method for measuring a process variable |
-
1980
- 1980-04-18 JP JP5152380A patent/JPS56148015A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS56148015A (en) | 1981-11-17 |
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