JP3062916B2 - 2-wire electromagnetic flowmeter - Google Patents
2-wire electromagnetic flowmeterInfo
- Publication number
- JP3062916B2 JP3062916B2 JP6187170A JP18717094A JP3062916B2 JP 3062916 B2 JP3062916 B2 JP 3062916B2 JP 6187170 A JP6187170 A JP 6187170A JP 18717094 A JP18717094 A JP 18717094A JP 3062916 B2 JP3062916 B2 JP 3062916B2
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- JP
- Japan
- Prior art keywords
- current
- measured value
- excitation
- exciting
- value
- 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
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Description
【０００１】[0001]
【産業上の利用分野】この発明は、各種プロセス系にお
いて導電性を有する流体の流量を測定する電磁流量計に
関し、特に直流電源に接続された２線のケーブルより電
源が供給され、このケーブルを介して計測値を出力する
２線式電磁流量計に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic flowmeter for measuring the flow rate of a fluid having conductivity in various kinds of process systems, and more particularly to a power supply which is supplied from a two-wire cable connected to a DC power supply. The present invention relates to a two-wire electromagnetic flow meter that outputs a measured value via a sensor.
【０００２】[0002]
【従来の技術】従来より、この種の２線式電磁流量計に
おいては、測定管内を流れる流体の流れ方向に対してそ
の磁界の発生方向を垂直として配置された励磁コイルへ
所定周波数で励磁電流を供給し、励磁コイルの発生磁界
と直交して測定管内に配置された電極間に得られる信号
起電力（流量に比例した信号）を検出し、この検出した
信号起電力に基づいてＣＰＵでの演算処理により計測値
を０〜１００％値として求め、直流電源（D.C.２４Ｖ）
を供給している２線のケーブルに流れる電流Ｉ（ケーブ
ル電流）を、上記求めた計測値に応じて４〜２０ｍＡの
電流範囲で調整するものとしている。この場合、励磁コ
イルへの励磁電圧ＶEXおよび励磁電流ＩEXは、ケーブル
に流れる上記電流範囲以下の電流を利用して作られる。
すなわち、計測値が４〜２０ｍＡ範囲の電流信号に変換
されるため、励磁回路では常に確保できる電流として４
ｍＡしか使用することができず、信号起電力を大きくと
るために４ｍＡ中の大部分を励磁電流ＩEX（ＩEX≒４ｍ
Ａ）としている。また、励磁電圧ＶEXは、６Ｖとしてい
る。2. Description of the Related Art Conventionally, in a two-wire type electromagnetic flowmeter of this type, an exciting current at a predetermined frequency is applied to an exciting coil arranged so that a magnetic field is generated in a direction perpendicular to a flow direction of a fluid flowing in a measuring tube. And detects a signal electromotive force (a signal proportional to the flow rate) obtained between the electrodes arranged in the measurement tube at right angles to the magnetic field generated by the excitation coil, and based on the detected signal electromotive force, The measured value is calculated as a 0 to 100% value by arithmetic processing, and a DC power supply (24 VDC)
Is adjusted in a current range of 4 to 20 mA according to the measured value obtained above. In this case, the excitation voltage V EX to the excitation coil and the excitation current I EX are created by using a current that flows through the cable and is equal to or less than the above current range.
That is, since the measured value is converted to a current signal in the range of 4 to 20 mA, the current that can always be secured by the excitation circuit is 4 mA.
mA can be used, and most of the 4 mA is excited by an exciting current I EX (I EX ≒ 4 m
A). The excitation voltage V EX is set to 6V.
【０００３】[0003]
【発明が解決しようとする課題】この２線式電磁流量計
において、信号起電力は、ｅ＝ｋ・Ｂ・ｖ・Ｄとして表
される。なお、この式において、ｋは定数、Ｄは測定管
の口径、ｖは平均流速、Ｂは発生磁束密度である。ここ
で、Ｂは励磁電流ＩEXに比例し、励磁電流ＩEXを大きく
すれば同じ流速でも信号起電力ｅが大きくなる。しか
し、従来においては、励磁電流ＩEXは上述した如く４ｍ
Ａに規定されている。このため、信号起電力ｅが小さ
く、流速に応じて電極に重畳してくるノイズの影響を受
けて出力が大きくふらつき、すなわち高流量になるにつ
れ信号起電力ｅに含まれるノイズレベルの割合が高くな
ってＳ／Ｎ比が低下し、安定した流量計測ができないと
いう問題があった。In this two-wire electromagnetic flow meter, the signal electromotive force is expressed as e = k ・ Bｖv ・ D. In this equation, k is a constant, D is the diameter of the measuring tube, v is the average flow velocity, and B is the generated magnetic flux density. Here, B is proportional to the exciting current I EX, the signal electromotive force e is greater at the same flow rate by increasing the exciting current I EX. However, conventionally, the exciting current I EX is 4 m as described above.
A. For this reason, the signal electromotive force e is small, and the output fluctuates greatly under the influence of noise superimposed on the electrode according to the flow velocity. In other words, as the flow rate increases, the ratio of the noise level included in the signal electromotive force e increases. As a result, there is a problem that the S / N ratio is lowered and stable flow rate measurement cannot be performed.
【０００４】なお、計測値に応じて、すなわち計測値に
応ずるケーブル電流Ｉ（４〜２０ｍＡ）を利用して、励
磁電流ＩEXを大きな値に切り換えることが考えられる。
例えば、計測値が５０％である場合に励磁電流ＩEXの切
り換えを行うものとすると、この計測値に応ずるケーブ
ル電流は１２ｍＡであり、励磁コイルには１２ｍＡ−４
ｍＡ＝８ｍＡの電流をさらに流すことができる。すなわ
ち、現在の４ｍＡに加えて８ｍＡ、合計１２ｍＡの電流
を流すことができ、３倍の信号起電力ｅを得ることがで
きる。しかし、実際には励磁電流ＩEXを流し過ぎると、
励磁コイルがその電流供給期間内では立ち上がらなくな
る。すなわち、その電流供給期間において、励磁電流Ｉ
EXに応じた規定の磁力を得ることができなくなる。この
ため、計測値に応ずるケーブル電流Ｉを利用して励磁電
流ＩEXを大きな値に切り換えるようにしたとしても、励
磁電流ＩEXはその電流供給期間内で励磁コイルが立ち上
がるところまでしか増大させることができない。したが
って、信号起電力ｅはあまり大きくならず、Ｓ／Ｎ比の
改善が悪く、流量計測が不安定となる問題は依然として
残る。It is conceivable to switch the excitation current I EX to a large value according to the measured value, that is, using the cable current I (4 to 20 mA) corresponding to the measured value.
For example, assuming that the excitation current I EX is switched when the measured value is 50%, the cable current corresponding to this measured value is 12 mA, and the excitation coil has a current of 12 mA-4.
A current of mA = 8 mA can further flow. That is, a current of 12 mA in total, that is, 8 mA in addition to the current 4 mA, can flow, and a triple signal electromotive force e can be obtained. However, actually, when the exciting current I EX flows too much,
The exciting coil does not rise during the current supply period. That is, during the current supply period, the exciting current I
The specified magnetic force according to EX cannot be obtained. Thus, by utilizing the cable current I of meeting the measured value even when to switch the exciting current I EX to a large value, the exciting current I EX is that only increase until it rises excitation coil in its current supply period Can not. Therefore, the signal electromotive force e is not so large, the S / N ratio is not improved well, and the problem of unstable flow rate measurement still remains.
【０００５】本発明はこのような課題を解決するために
なされたもので、その目的とするところは、Ｓ／Ｎ比を
上げ、高流量時においても安定した流量計測を行うこと
のできる２線式電磁流量計を提供することにある。The present invention has been made to solve such a problem, and an object of the present invention is to increase the S / N ratio so that a two-wire system capable of performing a stable flow rate measurement even at a high flow rate. An object of the present invention is to provide an electromagnetic flow meter of the type.
【０００６】[0006]
【課題を解決するための手段】このような目的を達成す
るために、その第１発明（請求項１に係る発明）は、上
述した２線式電磁流量計において、計測値が所定の％値
を越えた場合、この所定の％値を越える計測値に応ずる
ケーブル電流を利用し、励磁電圧ＶEXのＶEX1からＶ
EX2 への昇圧に併せ、励磁電流ＩEXをＩEX1 からＩEX2
へ増大するようにしたものである。また、その第２発明
（請求項２に係る発明）は、上述した２線式電磁流量計
において、計測値が第１の％値を越えた場合、この第１
の％値を越える計測値に応ずるケーブル電流を利用し、
励磁電圧ＶEXをＶEX1 からＶEX2 へ昇圧し、計測値が第
１の％値よりも高い第２の％値を越えた場合、この第２
の％値を越える計測値に応ずるケーブル電流を利用し、
励磁電圧ＶEXのＶEX1 からＶEX2 への昇圧に併せ、励磁
電流ＩEXをＩEX1 からＩEX2 へ増大するようにしたもの
である。In order to achieve the above object, the first invention (the invention according to claim 1) is a two-wire electromagnetic flowmeter, wherein the measured value is a predetermined% value. Is exceeded, the cable current corresponding to the measured value exceeding the predetermined% value is used to change the excitation voltage V EX from V EX1 to V EX1.
The excitation current I EX is changed from I EX1 to I EX2
To be increased. Further, the second invention (invention according to claim 2) is characterized in that, when the measured value exceeds the first% value in the above-described two-wire electromagnetic flow meter, the first
Using the cable current corresponding to the measured value exceeding the% value of
When the excitation voltage V EX is increased from V EX1 to V EX2 and the measured value exceeds a second% value higher than the first% value, the second
Using the cable current corresponding to the measured value exceeding the% value of
The excitation current I EX is increased from I EX1 to I EX2 in accordance with the step-up of the excitation voltage V EX from V EX1 to V EX2 .
【０００７】[0007]
【作用】したがってこの発明によれば、その第１発明で
は、例えば、計測値が５０％を越えた場合、この５０％
を越える計測値に応ずるケーブル電流Ｉ＝１２ｍＡを利
用し、励磁電圧ＶEXのＶEX1 ＝６ＶからＶEX2 ＝１０Ｖ
への昇圧に併せ、励磁電流ＩEXがＩEX1 ＝４ｍＡからＩ
EX2 ＝８ｍＡへ増大する。また、その第２発明では、例
えば、計測値が２５％を越えた場合、この２５％を越え
る計測値に応ずるケーブル電流Ｉ＝８ｍＡを利用し、励
磁電圧ＶEXがＶEX 1 ＝６ＶからＶEX2 ＝１０Ｖへ昇圧さ
れ、計測値が５０％を越えた場合、この５０％を越える
計測値に応ずるケーブル電流Ｉ＝１２ｍＡを利用し、励
磁電圧ＶEXのＶEX1 ＝６ＶからＶEX2 ＝１０Ｖへの昇圧
に併せ、励磁電流ＩEXがＩEX1 ＝４ｍＡからＩEX2 ＝８
ｍＡへ増大する。Therefore, according to the present invention, in the first invention, for example, when the measured value exceeds 50%, this 50%
Using the cable current I = 12 mA corresponding to the measured value exceeding V EX1 = 6 V of the excitation voltage V EX to V EX2 = 10 V
The excitation current I EX changes from I EX1 = 4 mA to I
EX2 increases to 8 mA. In the second invention, for example, when the measured value exceeds 25%, the exciting current V EX is changed from V EX 1 = 6V to V EX using the cable current I = 8 mA corresponding to the measured value exceeding 25%. When the measured value exceeds 50% and the measured value exceeds 50%, the cable current I = 12 mA corresponding to the measured value exceeding 50% is used to change the excitation voltage V EX from V EX1 = 6V to V EX2 = 10V. The excitation current I EX changes from I EX1 = 4 mA to I EX2 = 8
mA.
【０００８】[0008]
【実施例】以下、本発明を実施例に基づき詳細に説明す
る。図１はこの発明の一実施例を示す２線式電磁流量計
のブロック回路構成図である。同図において、１は測定
管、２は測定管１内を流れる流体の流れ方向に対してそ
の磁界の発生方向を垂直として配置された励磁コイル、
３は励磁コイル２へ矩形波状の励磁電流ＩEXを周期的に
供給する励磁回路、４ａ，４ｂは励磁コイル２の発生磁
界と直交して測定管１内に配置された検出電極、５は接
地電極、６は電極４ａ，４ｂ間に得られる信号起電力を
検出する信号起電力検出回路、７はこの信号起電力検出
回路６の検出する信号起電力をサンプルホールドするサ
ンプルホールド回路、８はＡ／Ｄ変換器、９はＣＰＵ、
１０はＤ／Ａ変換器、１１は出力回路、１２は昇圧回路
であり、この２線式電磁流量計１００はケーブルＬ１，
Ｌ２を介して直流電源（D.C.２４Ｖ）２００と接続され
ている。DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments. FIG. 1 is a block circuit configuration diagram of a two-wire electromagnetic flow meter showing one embodiment of the present invention. In the figure, 1 is a measuring tube, 2 is an excitation coil arranged so that the direction of generation of the magnetic field is perpendicular to the flow direction of the fluid flowing in the measuring tube 1,
3 periodically supplying excitation circuit exciting current I EX having a rectangular waveform to the excitation coil 2, 4a, 4b are detecting electrodes disposed within the measuring tube 1 and perpendicular to the magnetic field generated by the exciting coil 2, 5 ground Electrodes, 6 a signal electromotive force detection circuit for detecting the signal electromotive force obtained between the electrodes 4a and 4b, 7 a sample and hold circuit for sampling and holding the signal electromotive force detected by the signal electromotive force detection circuit 6, and 8 an A / D converter, 9 is a CPU,
Reference numeral 10 denotes a D / A converter, 11 denotes an output circuit, and 12 denotes a booster circuit.
It is connected to a DC power supply (DC 24 V) 200 via L2.
【０００９】励磁回路３は励磁電圧回路３−１，定電流
回路３−２および励磁電流スイッチング回路３−３を備
え、励磁電圧回路３−１と出力回路１１とはケーブルＬ
１，Ｌ２間に直列に接続されている。ケーブルＬ２と出
力回路１１との間にはスイッチＳＷ４が設けられ、この
スイッチＳＷ４と並列にスイッチＳＷ１を介して昇圧回
路１２が設けられている。定電流回路３−２は、トラン
ジスタＴｒ１，Ｔｒ２、抵抗Ｒ１〜Ｒ１２、コンバータ
ＣＰ１，ＣＰ２、ツェナーダイオードＺＤを備え、抵抗
Ｒ４と抵抗Ｒ５との直列回路に並列にスイッチＳＷ３が
設けられている。励磁電流スイッチング回路３−３はス
イッチＳＷ５〜ＳＷ８からなる。また、励磁電流スイッ
チング回路３−３と昇圧回路１２との間には、スイッチ
ＳＷ２が設けられている。これらスイッチＳＷ１〜ＳＷ
８はＣＰＵ９によりそのオン／オフ状況が制御される。The exciting circuit 3 includes an exciting voltage circuit 3-1, a constant current circuit 3-2, and an exciting current switching circuit 3-3. The exciting voltage circuit 3-1 and the output circuit 11 are connected to a cable L.
1 and L2 are connected in series. A switch SW4 is provided between the cable L2 and the output circuit 11, and a booster circuit 12 is provided in parallel with the switch SW4 via a switch SW1. The constant current circuit 3-2 includes transistors Tr1 and Tr2, resistors R1 to R12, converters CP1 and CP2, and a Zener diode ZD. A switch SW3 is provided in parallel with a series circuit including the resistors R4 and R5. The exciting current switching circuit 3-3 includes switches SW5 to SW8. A switch SW2 is provided between the exciting current switching circuit 3-3 and the booster circuit 12. These switches SW1 to SW
Reference numeral 8 denotes an on / off state controlled by the CPU 9.
【００１０】次に、この２線式電磁流量計１００の動作
について、ＣＰＵ９の機能を交えながら説明する。 〔計測値が０％から２５％の期間での動作〕この場合、
ＣＰＵ９によって、スイッチＳＷ１，ＳＷ２，ＳＷ３は
オフ、スイッチＳＷ４はオンに制御される。直流電源２
００からの電源の供給を受けて、ＣＰＵ９は、励磁電流
スイッチング回路３−３のスイッチＳＷ５〜ＳＷ８を駆
動する。これにより、励磁コイル２へ所定の周波数で矩
形波状の励磁電流ＩEXが流れる。この励磁電流ＩEXの大
きさは定電流回路３−２によって決定される。この場
合、定電流回路３−２は、スイッチＳＷ３がオフとされ
ていることから、励磁電流ＩEXを４ｍＡとする。また、
励磁コイル２への励磁電圧ＶEXは、スイッチＳＷ２がオ
フとされていることから、励磁電圧回路３−１によって
決定される。この場合、励磁電圧ＶEXは６Ｖとされる。Next, the operation of the two-wire electromagnetic flow meter 100 will be described with the function of the CPU 9. [Operation in a period where the measured value is 0% to 25%] In this case,
By the CPU 9, the switches SW1, SW2, and SW3 are turned off, and the switch SW4 is turned on. DC power supply 2
Upon receiving the power supply from 00, the CPU 9 drives the switches SW5 to SW8 of the exciting current switching circuit 3-3. As a result, the excitation current I EX having a rectangular waveform flows at a predetermined frequency into the excitation coil 2. The magnitude of the exciting current I EX is determined by the constant current circuit 3-2. In this case, since the switch SW3 is turned off, the constant current circuit 3-2 sets the exciting current I EX to 4 mA. Also,
The excitation voltage V EX to the excitation coil 2 is determined by the excitation voltage circuit 3-1 because the switch SW2 is turned off. In this case, the excitation voltage V EX is set to 6V.
【００１１】励磁コイル２へ所定の周波数で矩形波状の
励磁電流ＩEXが流れると測定管１内に交流磁界が発生す
る。これにより、電極４ａ，４ｂ間に流速と磁界との相
互作用により信号起電力が生じ、これが信号起電力検出
回路６で検出される。この検出される信号起電力はサン
プルホールド回路７でサンプルホールドされ、Ａ／Ｄ変
換器８を介してＣＰＵ９へ送られる。ＣＰＵ９は、送ら
れてくる信号起電力に基づいて所定の演算処理により計
測値を０〜１００％値として求め、この求めた計測値を
Ｄ／Ａ変換器１０を介して出力回路１１へ送る。出力回
路１１は、ケーブルＬ１，Ｌ２に流れる電流Ｉ（ケーブ
ル電流）を調整し、ＣＰＵ１０から送られてくる計測値
に応じた４〜２０ｍＡ範囲の値とする。これにより、計
測値が０％から２５％の期間では、図２に領域Ｉとして
示すように、励磁電流ＩEXをＩEX1 ＝４ｍＡ，励磁電圧
ＶEXをＶEX1 ＝６Ｖとして、ケーブル電流Ｉが４ｍＡか
ら８ｍＡの範囲で変化する。When a rectangular-wave-like exciting current I EX flows at a predetermined frequency to the exciting coil 2, an AC magnetic field is generated in the measuring tube 1. As a result, a signal electromotive force is generated between the electrodes 4a and 4b due to the interaction between the flow velocity and the magnetic field, and this is detected by the signal electromotive force detection circuit 6. The detected signal electromotive force is sampled and held by the sample and hold circuit 7 and sent to the CPU 9 via the A / D converter 8. The CPU 9 obtains a measured value as a value of 0 to 100% by a predetermined arithmetic processing based on the transmitted signal electromotive force, and sends the obtained measured value to the output circuit 11 via the D / A converter 10. The output circuit 11 adjusts the current I (cable current) flowing through the cables L1 and L2 to a value in the range of 4 to 20 mA according to the measurement value sent from the CPU 10. As a result, during a period in which the measured value is 0% to 25%, as shown as a region I in FIG. 2, the exciting current I EX is I EX1 = 4 mA, the exciting voltage V EX is V EX1 = 6 V, and the cable current I is It varies between 4 mA and 8 mA.
【００１２】〔計測値が２５％から５０％の期間での動
作〕計測値が２５％を越えると、ＣＰＵ９は、スイッチ
ＳＷ１，ＳＷ２をオン、スイッチＳＷ３，ＳＷ４をオフ
とする。これにより、２５％を越える計測値に応ずるケ
ーブル電流Ｉ（８ｍＡ）が昇圧回路１２へ供給され、こ
の昇圧回路１２での昇圧動作によって励磁電圧ＶEXが１
０Ｖとされる。なお、この場合、定電流回路３−２での
スイッチＳＷ３はオフとされたままであるので、励磁電
流ＩEXは４ｍＡのままとされる。すなわち、この場合、
昇圧回路１２で電流を必要とするので、すなわち励磁電
圧ＶEXの昇圧源を確保する必要があるので、励磁電流Ｉ
EXは４ｍＡのままとする。これにより、計測値が２５％
から５０％の期間では、図２に領域IIとして示すよう
に、励磁電流ＩEXをＩEX1 ＝４ｍＡ，励磁電圧ＶEXをＶ
EX2 ＝１０Ｖとして、ケーブル電流Ｉが８ｍＡから１２
ｍＡの範囲で変化する。[Operation in a Period Where the Measured Value is 25% to 50%] When the measured value exceeds 25%, the CPU 9 turns on the switches SW1 and SW2 and turns off the switches SW3 and SW4. As a result, the cable current I (8 mA) corresponding to the measured value exceeding 25% is supplied to the booster circuit 12, and the boosting operation in the booster circuit 12 causes the excitation voltage V EX to become 1
0V. In this case, since the switch SW3 in the constant current circuit 3-2 is kept off, the exciting current I EX is kept at 4 mA. That is, in this case,
Since a current is required in the booster circuit 12, that is, it is necessary to secure a boost source of the excitation voltage V EX , the excitation current I
EX remains at 4 mA. As a result, the measured value is 25%
In the period from 50% to 50%, as shown as region II in FIG. 2, the exciting current I EX is I EX1 = 4 mA, and the exciting voltage V EX is V
Assuming that EX2 = 10V, the cable current I is 8 mA to 12
It changes within the range of mA.
【００１３】〔計測値が５０％から１００％の期間での
動作〕計測値が５０％を越えると、ＣＰＵ９は、スイッ
チＳＷ１，ＳＷ２，ＳＷ３をオン、スイッチＳＷ４をオ
フとする。これにより、５０％を越える計測値に応ずる
ケーブル電流Ｉ（１２ｍＡ）が昇圧回路１２へ供給さ
れ、この昇圧回路１２での昇圧動作によって励磁電圧Ｖ
EXは、先の２５％から５０％の期間の場合と同様、１０
Ｖとされる。また、定電流回路３−２でのスイッチＳＷ
３がオンとされることから、励磁電流ＩEXはそれまでの
４ｍＡから８ｍＡに増大する。すなわち、この場合、ケ
ーブル電流Ｉより励磁電圧ＶEXの昇圧源とは別に、１２
ｍＡ−８ｍＡ＝４ｍＡの電流を確保することができるの
で、励磁電流ＩEXを８ｍＡへ増大する。これにより、計
測値が５０％から１００％の期間では、図２に領域III
として示すように、励磁電流ＩEXをＩEX2 ＝８ｍＡ，励
磁電圧ＶEXをＶEX2 ＝１０Ｖとして、ケーブル電流Ｉが
１２ｍＡから２０ｍＡの範囲で変化する。すなわち、本
実施例では、計測値が５０％に達した以降、励磁電圧Ｖ
EXの昇圧によって励磁コイル２の立ち上がりを早くして
励磁電流ＩEXを大とすることができている。これによっ
て、本実施例によれば、計測値が５０％に達した以降、
信号起電力が大きくなり、Ｓ／Ｎ比を上げ、高流量時に
おいても安定した流量計測が可能となる。[Operation in a Period where the Measured Value is 50% to 100%] When the measured value exceeds 50%, the CPU 9 turns on the switches SW1, SW2 and SW3 and turns off the switch SW4. As a result, the cable current I (12 mA) corresponding to the measured value exceeding 50% is supplied to the booster circuit 12, and the boosting operation in the booster circuit 12 causes the excitation voltage V
EX is 10%, as in the previous 25% to 50% period.
V. The switch SW in the constant current circuit 3-2
Since 3 is turned on, the exciting current I EX increases from 4 mA to 8 mA. That is, in this case, apart from the boosting source of excitation voltage V EX than cable current I, 12
Since a current of mA-8 mA = 4 mA can be secured, the exciting current I EX is increased to 8 mA. As a result, in the period where the measured value is 50% to 100%, FIG.
Assuming that the exciting current I EX is I EX2 = 8 mA and the exciting voltage V EX is V EX2 = 10 V, the cable current I changes in the range of 12 mA to 20 mA. That is, in this embodiment, after the measured value reaches 50%, the excitation voltage V
By boosting the EX and faster rise of the exciting coil 2 the exciting current I EX is able to large. Thereby, according to the present embodiment, after the measured value reaches 50%,
The signal electromotive force is increased, the S / N ratio is increased, and stable flow measurement can be performed even at a high flow rate.
【００１４】なお、本実施例では、計測値が２５％から
５０％の期間において励磁電圧ＶEXをＶEX2 ＝１０Ｖと
したが、ＶEX1 ＝６Ｖのままとしてもよい。すなわち、
計測値が５０％を越えた場合に初めて、励磁電圧ＶEXを
ＶEX2 ＝１０Ｖに、励磁電流ＩEXをＩEX2 ＝８ｍＡにす
るようにしてもよい。また、上述では、計測値の上昇過
程で説明したが、下降過程でも同様の動作（逆動作）が
行われることは言うまでもない。In this embodiment, the excitation voltage V EX is set to V EX2 = 10 V in a period in which the measured value is 25% to 50%, but V EX1 may be kept at 6 V. That is,
Only when the measured value exceeds 50%, the excitation voltage V EX may be set to V EX2 = 10 V and the excitation current I EX may be set to I EX2 = 8 mA. In the above description, the description has been given of the process of increasing the measured value, but it goes without saying that the same operation (reverse operation) is performed in the process of decreasing the measured value.
【００１５】[0015]
【発明の効果】以上説明したことから明らかなように本
発明によれば、その第１発明では、計測値が所定の％値
を越えた場合、この所定の％値を越える計測値に応ずる
ケーブル電流を利用し、励磁電圧ＶEXのＶEX1 からＶ
EX2 への昇圧に併せ、励磁電流ＩEXがＩEX1 からＩEX2
へ増大するものとなり、計測値が所定の％値を越えた以
降、励磁電圧ＶEXの昇圧によって励磁コイルの立ち上が
りを早くして励磁電流ＩEXを大とすることが可能とな
る。これによって、、計測値が所定の％値に達した以
降、信号起電力を大きくし、Ｓ／Ｎ比を上げ、高流量時
においても安定した流量計測を行うことが可能となる。
また、その第２発明では、計測値が第１の％値を越えた
場合、この第１の％値を越える計測値に応ずるケーブル
電流を利用し、励磁電圧ＶEXがＶEX1 からＶEX 2 へ昇圧
され、計測値が第２の％値を越えた場合、この第２の％
値を越える計測値に応ずるケーブル電流を利用し、励磁
電圧ＶEXのＶEX1 からＶEX2 への昇圧に併せ、励磁電流
ＩEXがＩEX1 からＩEX2 へ増大するものとなり、第１の
％値に応ずるケーブル電流により励磁電圧ＶEXの昇圧源
を確保のうえ、また第２の％値に応ずるケーブル電流に
より励磁電流ＩEXの増大源を確保のうえ、計測値が第２
の％値を越えた以降、励磁電圧ＶEXの昇圧によって励磁
コイルの立ち上がりを早くして励磁電流ＩEXを大とする
ことが可能となる。これによって、計測値が第２の％値
に達した以降、信号起電力を大きくし、Ｓ／Ｎ比を上
げ、高流量時においても安定した流量計測を行うことが
可能となる。As is apparent from the above description, according to the present invention, in the first invention, when the measured value exceeds a predetermined% value, a cable corresponding to the measured value exceeding the predetermined% value is used. Using the current, V EX1 to V EX of the excitation voltage V EX
As the voltage rises to EX2 , the exciting current I EX changes from I EX1 to I EX2
It shall be increased to, after the measured value exceeds a predetermined percentage value, and quickly rise of the exciting coil by the boost of the exciting voltage V EX becomes possible to a large exciting current I EX. As a result, after the measured value reaches the predetermined% value, the signal electromotive force is increased, the S / N ratio is increased, and stable flow measurement can be performed even at a high flow rate.
Further, in the second invention, when the measured value exceeds the first% value, the excitation voltage V EX is changed from V EX1 to V EX 2 by using a cable current corresponding to the measured value exceeding the first% value. If the measured value exceeds the second% value, the second%
Using the cable current corresponding to the measured value exceeding the value, the exciting current I EX increases from I EX1 to I EX2 in accordance with the step-up of the exciting voltage V EX from V EX1 to V EX2 , and the first% value In addition to securing the boost source of the excitation voltage V EX by the cable current corresponding to the above, and securing the source of increase of the excitation current I EX by the cable current corresponding to the second% value, the measured value becomes the second value.
%, The rising of the exciting voltage V EX makes the exciting coil rise faster to increase the exciting current I EX . Thus, after the measured value reaches the second% value, it is possible to increase the signal electromotive force, increase the S / N ratio, and perform a stable flow rate measurement even at a high flow rate.
【図１】 本発明の一実施例を示す２線式電磁流量計の
ブロック回路構成図である。FIG. 1 is a block circuit configuration diagram of a two-wire electromagnetic flow meter showing one embodiment of the present invention.
【図２】 この２線式電磁流量計における計測値とケー
ブル電流との関係および励磁電圧，励磁電流との関係を
示す図である。FIG. 2 is a diagram showing a relationship between a measured value and a cable current and a relationship between an excitation voltage and an excitation current in the two-wire electromagnetic flow meter.
１…測定管、２…励磁コイル、３…励磁回路、３−１…
励磁電圧回路、３−２…定電流回路、３−３…励磁電流
スイッチング回路、４ａ，４ｂ…検出電極、５…接地電
極、６…信号起電力検出回路、７…サンプルホールド回
路、８…Ａ／Ｄ変換器、９…ＣＰＵ、１０…Ｄ／Ａ変換
器、１１…出力回路、１２…昇圧回路、ＳＷ１〜ＳＷ８
…スイッチ、１００…２線式電磁流量計、Ｌ１，Ｌ２…
ケーブル、２００…直流電源。DESCRIPTION OF SYMBOLS 1 ... Measurement tube, 2 ... Excitation coil, 3 ... Excitation circuit, 3-1 ...
Excitation voltage circuit, 3-2 constant current circuit, 3-3 excitation current switching circuit, 4a, 4b detection electrode, 5 ground electrode, 6 signal electromotive force detection circuit, 7 sample hold circuit, 8 A / D converter, 9 CPU, 10 D / A converter, 11 output circuit, 12 booster circuit, SW1 to SW8
... Switch, 100 ... 2-wire electromagnetic flow meter, L1, L2 ...
Cable, 200 ... DC power supply.
───────────────────────────────────────────────────── フロントページの続き (58)調査した分野(Int.Cl.7，ＤＢ名) G01F 1/60 ──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. 7 , DB name) G01F 1/60
Claims (2)
てその磁界の発生方向を垂直として配置された励磁コイ
ルへ所定周波数で励磁電流を供給し、前記励磁コイルの
発生磁界と直交して前記測定管内に配置された電極間に
得られる信号起電力を検出し、この信号起電力に基づい
て計測値を０〜１００％値として求め、この求めた計測
値に応じて直流電源を供給している２線のケーブルに流
れる電流を所定の電流範囲で調整する一方、このケーブ
ルに流れる前記電流範囲以下の電流を利用して前記励磁
コイルへの励磁電圧ＶEXおよび励磁電流ＩEXを作る２線
式電磁流量計において、 前記計測値が所定の％値を越えた場合、この所定の％値
を越える計測値に応ずるケーブル電流を利用し、前記励
磁電圧ＶEXのＶEX1 からＶEX2 への昇圧に併せ、前記励
磁電流ＩEXをＩEX1 からＩEX2 へ増大する制御手段を備
えたことを特徴とする２線式電磁流量計。An exciting current is supplied at a predetermined frequency to an exciting coil arranged so that the direction of generation of a magnetic field is perpendicular to the direction of flow of a fluid flowing in a measurement tube, and the exciting current is orthogonal to the generated magnetic field of the exciting coil. A signal electromotive force obtained between electrodes arranged in the measurement tube is detected, a measured value is determined as a value of 0 to 100% based on the signal electromotive force, and a DC power is supplied according to the measured value. The current flowing through the two-wire cable is adjusted within a predetermined current range, and the current flowing through the cable and less than the current range is used to generate the excitation voltage V EX to the excitation coil and the excitation current I EX. In the electromagnetic flow meter, when the measured value exceeds a predetermined% value, the excitation voltage V EX is stepped up from V EX1 to V EX2 by using a cable current corresponding to the measured value exceeding the predetermined% value. According to the above A two-wire electromagnetic flow meter comprising control means for increasing an exciting current I EX from I EX1 to I EX2 .
てその磁界の発生方向を垂直として配置された励磁コイ
ルへ所定周波数で励磁電流を供給し、前記励磁コイルの
発生磁界と直交して前記測定管内に配置された電極間に
得られる信号起電力を検出し、この信号起電力に基づい
て計測値を０〜１００％値として求め、この求めた計測
値に応じて直流電源を供給している２線のケーブルに流
れる電流を所定の電流範囲で調整する一方、このケーブ
ルに流れる前記電流範囲以下の電流を利用して前記励磁
コイルへの励磁電圧ＶEXおよび励磁電流ＩEXを作る２線
式電磁流量計において、 前記計測値が第１の％値を越えた場合、この第１の％値
を越える計測値に応ずるケーブル電流を利用し、前記励
磁電圧ＶEXをＶEX1 からＶEX2 へ昇圧し、前記計測値が
前記第１の％値よりも高い第２の％値を越えた場合、こ
の第２の％値を越える計測値に応ずるケーブル電流を利
用し、前記励磁電圧ＶEXのＶEX1 からＶEX2 への昇圧に
併せ、前記励磁電流ＩEXをＩEX1 からＩEX2 へ増大する
制御手段を備えたことを特徴とする２線式電磁流量計。2. An exciting current is supplied at a predetermined frequency to an exciting coil arranged so that its magnetic field generation direction is perpendicular to the flow direction of a fluid flowing through the measuring tube, and the excitation current is orthogonal to the magnetic field generated by the excitation coil. A signal electromotive force obtained between electrodes arranged in the measurement tube is detected, a measured value is determined as a value of 0 to 100% based on the signal electromotive force, and a DC power is supplied according to the measured value. The current flowing through the two-wire cable is adjusted within a predetermined current range, and the current flowing through the cable and less than the current range is used to generate the excitation voltage V EX to the excitation coil and the excitation current I EX. When the measured value exceeds the first% value, the exciting voltage V EX is changed from V EX1 to V EX2 by using a cable current corresponding to the measured value exceeding the first% value. Boost the measured value Exceeds a second percentage value higher than the first percentage value, the cable current corresponding to the measured value exceeding the second percentage value is used to change the excitation voltage V EX from V EX1 to V EX2 . 2. A two-wire electromagnetic flow meter comprising control means for increasing the exciting current I EX from I EX1 to I EX2 in accordance with the step-up.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6187170A JP3062916B2 (en) | 1994-08-09 | 1994-08-09 | 2-wire electromagnetic flowmeter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6187170A JP3062916B2 (en) | 1994-08-09 | 1994-08-09 | 2-wire electromagnetic flowmeter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0850043A JPH0850043A (en) | 1996-02-20 |
| JP3062916B2 true JP3062916B2 (en) | 2000-07-12 |
Family
ID=16201344
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6187170A Expired - Lifetime JP3062916B2 (en) | 1994-08-09 | 1994-08-09 | 2-wire electromagnetic flowmeter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3062916B2 (en) |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19938160C2 (en) * | 1999-08-16 | 2003-11-20 | Krohne Messtechnik Kg | Magnetic-inductive flow measuring method and flow meter |
| JP4300562B2 (en) * | 2000-03-30 | 2009-07-22 | 横河電機株式会社 | Electromagnetic flow meter |
| JP4378765B2 (en) * | 2000-12-26 | 2009-12-09 | 横河電機株式会社 | Excitation circuit of electromagnetic flow meter |
| JP4110442B2 (en) * | 2001-05-14 | 2008-07-02 | 横河電機株式会社 | Electromagnetic flow meter |
| DE10200768B4 (en) * | 2001-12-06 | 2004-03-11 | Krohne Ag | Mass flow meter and method for operating a mass flow meter |
| JP3996464B2 (en) * | 2002-07-31 | 2007-10-24 | 株式会社山武 | 2-wire electromagnetic flow meter |
| JP5065620B2 (en) * | 2006-05-23 | 2012-11-07 | 株式会社キーエンス | Electromagnetic flow meter |
| JP6806532B2 (en) * | 2016-11-09 | 2021-01-06 | アズビル株式会社 | Excitation circuit of electromagnetic flowmeter, and electromagnetic flowmeter |
-
1994
- 1994-08-09 JP JP6187170A patent/JP3062916B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0850043A (en) | 1996-02-20 |
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