JPH0228807B2 - DENJIRYURYOKEI - Google Patents
DENJIRYURYOKEIInfo
- Publication number
- JPH0228807B2 JPH0228807B2 JP7136481A JP7136481A JPH0228807B2 JP H0228807 B2 JPH0228807 B2 JP H0228807B2 JP 7136481 A JP7136481 A JP 7136481A JP 7136481 A JP7136481 A JP 7136481A JP H0228807 B2 JPH0228807 B2 JP H0228807B2
- Authority
- JP
- Japan
- Prior art keywords
- excitation
- noise
- signal
- periods
- circuit
- 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
Links
- 230000005284 excitation Effects 0.000 claims description 24
- 238000005070 sampling Methods 0.000 claims description 16
- 230000005674 electromagnetic induction Effects 0.000 claims description 14
- 230000005279 excitation period Effects 0.000 claims description 10
- 230000004907 flux Effects 0.000 claims description 2
- 238000012545 processing Methods 0.000 description 13
- 239000012530 fluid Substances 0.000 description 6
- 238000000034 method Methods 0.000 description 5
- 230000004044 response Effects 0.000 description 5
- 230000008859 change Effects 0.000 description 4
- 230000001360 synchronised effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 3
- 238000007796 conventional method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000002123 temporal effect Effects 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】
本発明は電磁流量計の励磁方式とそれに伴う信
号処理の改良に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation method for an electromagnetic flowmeter and an improvement in signal processing associated therewith.
一般に電磁流量計においてその電磁流量計発信
器の電極間に発生する電圧は、(1)流体の流速に比
例する信号電圧、(2)励磁の磁束密度が時間的に変
化することに起因して発生する電磁誘導ノイズ電
圧、(3)電極と流体の間で電気化学的に発生し、し
かも緩慢ながら時間的に変化する直流ノイズ電
圧、(4)商用電源に起因する商用周波ノイズ電圧、
の４つがある。 Generally, in an electromagnetic flowmeter, the voltage generated between the electrodes of the electromagnetic flowmeter transmitter is caused by (1) a signal voltage proportional to the flow velocity of the fluid, and (2) a temporal change in the excitation magnetic flux density. electromagnetic induction noise voltage generated; (3) DC noise voltage that is electrochemically generated between the electrode and fluid and changes slowly over time; (4) commercial frequency noise voltage caused by commercial power supply;
There are four.
電磁流量計としては、これら４つの電圧のう
ち、(1)の信号電圧だけを得る必要がある。そこ
で、例えば矩形波励振などの低周波励振形の電磁
流量計が従来から用いられており、下記(A)〜(D)の
技術が知られている。 As an electromagnetic flowmeter, it is necessary to obtain only the signal voltage (1) among these four voltages. Therefore, electromagnetic flowmeters of low frequency excitation type, such as rectangular wave excitation, have been used for a long time, and the following techniques (A) to (D) are known.
(A) 特開昭53−75966号；「電磁流量計」
(B) 特公昭54−39750号；「交流式電磁血流量計」
(C) 特開昭50−128551号；「２つの磁気誘導時間
で切換られる直流磁界を用いた電磁流量計の電
気化学的障害直流電圧補償方式」
(D) 特開昭54−89658号；「誘導型流量測定方法お
よび装置」
しかし従来の低周波励振形の電磁流量計には、
(2)の電磁誘導ノイズ電圧、(3)の電気化学的な直流
ノイズ電圧及び(4)の商用周波ノイズ電圧を十分に
除去でき、且つ出力応答特性が早くて回路構成が
簡単であるというものは見当らない。つまり、
(イ) 電磁誘導ノイズ電圧があると流体の流速がゼ
ロであつても一定の出力となつて現われてこれ
がゼロ点バイアスとなるため、その都度流体を
止めてゼロ点調整を行う必要がある。しかし一
旦ゼロ点調整を行つたとしても、例えば電極表
面に絶性の付着物が付いたりすると、電磁誘導
ノイズ量が変つてしまうためゼロ点変動を生じ
てしまう。前記従来技術(A)と(B)ではこの問題の
改善が図られているが、(C)と(D)では改善されて
いないため励磁周波数をできるだけ低くするこ
とでノイズから逃れる必要があり、この結果、
応答性能が悪くなる欠点があつた。(A) JP-A No. 53-75966; “Electromagnetic flow meter” (B) JP-A No. 54-39750; “AC electromagnetic flow meter” (C) JP-A No. 50-128551; “Two magnetic induction ``Electrochemical disturbance DC voltage compensation method for electromagnetic flowmeter using time-switched DC magnetic field'' (D) JP-A-54-89658; ``Inductive flow measurement method and device'' However, the conventional low frequency excitation type The electromagnetic flowmeter has
It can sufficiently remove (2) electromagnetic induction noise voltage, (3) electrochemical DC noise voltage, and (4) commercial frequency noise voltage, and has fast output response characteristics and a simple circuit configuration. I can't find it. In other words, (a) If there is an electromagnetic induction noise voltage, it will appear as a constant output even if the fluid flow velocity is zero, and this will become the zero point bias, so it is necessary to stop the fluid and adjust the zero point each time. be. However, even if the zero point is once adjusted, if, for example, permanent deposits are attached to the electrode surface, the amount of electromagnetic induction noise will change, resulting in a zero point fluctuation. Although this problem has been improved in the conventional techniques (A) and (B), it has not been improved in (C) and (D), so it is necessary to avoid noise by lowering the excitation frequency as much as possible. As a result,
It had the disadvantage of poor response performance.
(ロ) 一方、従来技術(C)と(D)では電気化学的直流ノ
イズ電圧を除去するための補償手段が図られて
いるが、(A)と(B)ではこの補償手段が講じられて
いないため電気化学的直流ノイズ電圧が時間的
に変動した場合は出力に誤差がでたり、ひげ状
のノイズがでる欠点があるため、電気化学的直
流ノイズ電圧の変動し易いスラリー流体測定に
(A)と(B)は不向きであつた。(b) On the other hand, in the conventional techniques (C) and (D), compensation means are taken to remove electrochemical DC noise voltage, but in (A) and (B), this compensation means is not taken. Therefore, if the electrochemical DC noise voltage fluctuates over time, there will be an error in the output or whisker-like noise will appear.
(A) and (B) were unsuitable.
(ハ) また工業用電磁流量計では、商用電源からの
誘導ノイズが電源に混入した場合に誤差となる
が、この場合の対策も必要である。(c) In addition, industrial electromagnetic flowmeters cause errors when inductive noise from commercial power sources enters the power supply, and countermeasures are also required in this case.
そこで商用周波ノイズ電圧、電気化学的直流ノ
イズ電圧及び電磁誘導ノイズ電圧を十分に除去で
きしかも出力応答特性が早く構成の簡単な電磁流
量計の開発が進められている。この場合、サンプ
リングにより得た複数のサンプル値を演算処理し
て上記３種のノイズ成分を除去することが行われ
る。しかし、実際の電磁流量計の設置環境では付
近を商用周波数の大電流が流れる場合があり、商
用周波のノーマルモードノイズが大きく重畳する
ことがある。そのため、演算処理に必要な増幅器
やアナログ−デジタル変換器のダイナミツクレン
ジを大ノイズを許容できる程度まで広くしておか
ねばならないという問題が生じる。特にマイクロ
コンピユータにより演算処理する場合に必要とな
るアナログ−デジタル変換器はダイナミツクレン
ジが広いと極めて高価である。 Therefore, the development of an electromagnetic flowmeter that can sufficiently eliminate commercial frequency noise voltage, electrochemical DC noise voltage, and electromagnetic induction noise voltage, has fast output response characteristics, and has a simple configuration is underway. In this case, the three types of noise components mentioned above are removed by arithmetic processing of a plurality of sample values obtained by sampling. However, in the actual installation environment of an electromagnetic flowmeter, a large current at a commercial frequency may flow nearby, and a large amount of normal mode noise at the commercial frequency may be superimposed. Therefore, a problem arises in that the dynamic range of amplifiers and analog-to-digital converters required for arithmetic processing must be widened to the extent that large noises can be tolerated. In particular, the analog-to-digital converter required for arithmetic processing by a microcomputer is extremely expensive if the dynamic range is wide.
本発明は商用周波ノイズ、電気化学的直流ノイ
ズ及び電磁誘導ノイズを十分に除去できしかも出
力応答特性が早く構成が簡単な電磁流量計である
ことはもとより、演算処理に必要な機器のダイナ
ミツクレンジが狭くて済む電磁流量計を提供する
ことを目的とする。そのため、本発明ではノイズ
成分のうち相当大きいと予想される商用周波ノイ
ズを予め除去したのち他のノイズ成分を除去する
という信号処理を採用する。以下、図面を参照し
て本発明を実施例とともに説明する。 The present invention is an electromagnetic flowmeter that can sufficiently eliminate commercial frequency noise, electrochemical DC noise, and electromagnetic induction noise, has fast output response characteristics, and is simple in configuration. The purpose of the present invention is to provide an electromagnetic flowmeter that requires only a small space. Therefore, the present invention employs signal processing in which commercial frequency noise, which is expected to be quite large, is removed in advance among the noise components, and then other noise components are removed. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below along with examples with reference to the drawings.
第１図に本発明の一実施例の全体構成を示し、
第２図にその動作タイミングを示す。この例は励
磁のサイクルとして休止期間を介在して相互に反
対の極性で励磁するサイクルを採用した例であ
る。第１図において、１は励磁コイルであり、こ
の例では流体の流れ方向と電極３ａ，３ｂの取付
方向とにそれぞれ直交する磁界を発生するもので
ある。２は流体を流すための絶縁導管、４と５は
電極に高インピーダンスで接続されたバツフアア
ンプ、６は外部抵抗R1〜R4を有する差動アンプ
である。７は演算制御回路であり、この例では２
つのサンプルホールド回路８，９、増幅器１０、
及びマイロコンピユータによる演算回路１１で構
成してある。演算回路１１中で、１１ａはアナロ
グ−デジタル変換器（以下、Ａ／Ｄ変換器と略称
する）、１１ｂはマイクロプロセツサ、１１ｃは
メモリ、１１ｄは入出力ポート（以下、Ｉ／Ｏポ
ートと略称する）、１１ｅデジタル−アナログ変
換器（以下、Ｄ／Ａ変換器と略称する）、１１ｆ
はアドレス・バス、１１ｇはデータ・バスであ
る。 FIG. 1 shows the overall configuration of an embodiment of the present invention,
FIG. 2 shows the operation timing. This example is an example in which a cycle of excitation with mutually opposite polarities with a pause period in between is adopted as the excitation cycle. In FIG. 1, reference numeral 1 denotes an excitation coil, which in this example generates a magnetic field perpendicular to the direction of fluid flow and the mounting direction of electrodes 3a and 3b. 2 is an insulated conduit for flowing fluid; 4 and 5 are buffer amplifiers connected to electrodes at high impedance; and 6 is a differential amplifier having external resistors R1 to R4 . 7 is an arithmetic control circuit; in this example, 2
sample and hold circuits 8, 9, amplifier 10,
and an arithmetic circuit 11 using a microcomputer. In the arithmetic circuit 11, 11a is an analog-digital converter (hereinafter abbreviated as A/D converter), 11b is a microprocessor, 11c is a memory, and 11d is an input/output port (hereinafter abbreviated as I/O port). ), 11e digital-to-analog converter (hereinafter abbreviated as D/A converter), 11f
is an address bus, and 11g is a data bus.
励磁コイル１は直流定電流源１２に電界効果ト
ランジスタなどのスイツチ素子SW1-a，SW1-b，
SW2-a，SW2-bを介して接続され、各スイツチ素
子が演算回路１１内のＩ／Ｏポート１１ｄからの
タイミング信号１３により第２図ａ，ｂの波形で
開閉することによつて商用周波数の1/4の周波数
で第２図ｃに示す低周波矩形波状状の励磁電流が
流れる。第２図ｃ中、正の励磁期間Ａ、負の励磁
期間Ｂ及び各休止期間Ｃ、Ｄは同じ時間幅とされ
ている。 The excitation coil 1 includes a DC constant current source 12 and switch elements such as field effect transistors SW 1-a , SW 1-b ,
SW 2-a and SW 2-b are connected to each other, and each switch element is opened and closed according to the waveforms shown in FIG. A low frequency rectangular waveform excitation current shown in FIG. 2c flows at a frequency of 1/4 of the commercial frequency. In FIG. 2c, the positive excitation period A, the negative excitation period B, and each of the rest periods C and D have the same time width.
信号処理について述べると、差動アンプ６の出
力はサンプルホールド回路８，９によりサンプリ
ングされるが、サンプルホールド回路の各スイツ
チ素子SW3-a，SW3-bは演算回路１１からのタイ
ミング信号１４によつて第２図ｄ，ｅ，ｆに示す
如く商用周波数に同期して開閉され、励磁サイク
ルの各期間Ａ、Ｂ、Ｃ、Ｄ毎に２回のサンプリン
グが第２図ｇのタイミングで行われる。なお、第
２図ｄは商用周波数の波形を示す。各サンプルホ
ールド回路８，９の出力はそれぞれ抵抗R5，R6
を介して増幅器１０の入力端子に接続されてお
り、この接続により各期間の２つのサンプル値が
加算され、増幅器の入力前に商用周波ノイズが除
去される。即ち、
今、サンプリングの処理サイクルを第２図ｇに
おけるt1〜t8のタイミングにとり、各タイミング
のサンプル値をv1〜v8とすれば増幅器１０はV1
＝v1＋v2、V2＝v3＋v4、V3＝v5＋v6及びV4＝v7
＋v8なる４つの加算値が入力される。ここで電極
からの信号の成分を考えると、差動アンプ６の出
力には、第２図ｈに示す流量と励磁電流に比例す
る流量比例信号、同図ｉに示す商用周波ノイズ成
分、同図ｊに示す電気化学的直流ノイズ成分、並
びに同図ｋに示す電磁誘導ノイズ成分が含まれて
いる。これらの各成分は斜線を付した部分が重畳
してサンプリングされるが、サンプリングが商用
周波数に同期していること、及び電気化学的直流
ノイズは励磁の１サイクル程度の短時間では時間
に対して一定変化率で変化する電圧とみなせるこ
とにより、各サンプル値v1〜v8は次式(1)の値をと
る。 Regarding signal processing, the output of the differential amplifier 6 is sampled by the sample and hold circuits 8 and 9, and each switch element SW 3-a and SW 3-b of the sample and hold circuit receives the timing signal 14 from the arithmetic circuit 11. The circuit is opened and closed in synchronization with the commercial frequency as shown in Figure 2 d, e, and f, and sampling is performed twice for each period A, B, C, and D of the excitation cycle at the timing shown in Figure 2 g. be exposed. Note that FIG. 2d shows a waveform of a commercial frequency. The outputs of each sample and hold circuit 8 and 9 are connected to resistors R 5 and R 6 , respectively.
is connected to the input terminal of the amplifier 10 via this connection, the two sample values of each period are summed and main frequency noise is removed before input to the amplifier. That is, if the sampling processing cycle is set at the timings t1 to t8 in FIG. 2g, and the sample values at each timing are set to v1 to v8 , the amplifier 10 will be
= v 1 + v 2 , V 2 = v 3 + v 4 , V 3 = v 5 + v 6 and V 4 = v 7
Four additional values of + v8 are input. Considering the signal components from the electrodes, the output of the differential amplifier 6 includes a flow rate proportional signal proportional to the flow rate and exciting current shown in Fig. 2h, a commercial frequency noise component shown in Fig. 2I, and a commercial frequency noise component shown in Fig. 2I. The electrochemical direct current noise component shown in j and the electromagnetic induction noise component shown in k in the figure are included. Each of these components is sampled with the shaded area superimposed, but it is important to note that the sampling is synchronized with the commercial frequency and that electrochemical DC noise changes over time in a short period of time, such as one cycle of excitation. Since it can be regarded as a voltage that changes at a constant rate of change, each sample value v 1 to v 8 takes the value of the following equation (1).
v1＝v0＋ｆ＋Ｅ＋d1
v2＝v0−ｆ＋Ｅ＋ΔE＋d2
v3＝ｆ＋Ｅ＋2ΔE−d1
v4＝−ｆ＋Ｅ＋3ΔE−d2
v5＝−v0＋ｆ＋Ｅ＋4ΔE＋d1
v6＝−v0−ｆ＋Ｅ＋5ΔE＋d2
v7＝ｆ＋Ｅ＋6ΔE−d1
v8＝−ｆ＋Ｅ＋7ΔE−d2 ………式(1)
但し式(1)中、v0は流量比例信号、ｆは商用周波
ノイズ成分、Ｅは最初のサンプリングにおける電
気化学的直流ノイズ成分、ΔEはサンプリング毎
の電気化学的直流ノイズ成分の変化量、d1とd2は
電磁誘導ノイズ成分の各値である。v 1 = v 0 +f+E+d 1 v 2 = v 0 −f+E+ΔE+d 2 v 3 = f+E+2ΔE−d 1 v 4 = −f+E+3ΔE−d 2 v 5 = −v 0 +f+E+4ΔE+d 1 v 6 = −v 0 −f+E+5ΔE+d 2 v 7 = f+E+6ΔE−d 1 v 8 =−f+E+7ΔE−d 2 ………Equation (1) However, in Equation (1), v 0 is the flow rate proportional signal, f is the commercial frequency noise component, and E is the electrochemical direct current at the first sampling. The noise component, ΔE, is the amount of change in the electrochemical DC noise component for each sampling, and d 1 and d 2 are the respective values of the electromagnetic induction noise component.
したがつて、増幅器１０へ入力される４つの加
算値V1〜V4は次式(2)に与えられ、商用周波ノイ
ズが除去されていることがわかる。 Therefore, it can be seen that the four summed values V 1 to V 4 input to the amplifier 10 are given by the following equation (2), and commercial frequency noise is removed.
V1＝2v0＋2E＋ΔE＋d1＋d2
V2＝2E＋5ΔE−d1−d2
V3＝−2v0＋2E＋9ΔE＋d1＋d2
V4＝2E＋13ΔE−d1−d2 ………式(2)
これにより、演算回路１１の入力部であるＡ／
Ｄ変換器１１ａのダイナミツクレンジは、商用周
波ノイズを考慮しない狭いもので良いことにな
る。V 1 =2v 0 +2E+ΔE+d 1 +d 2 V 2 =2E+5ΔE−d 1 −d 2 V 3 =−2v 0 +2E+9ΔE+d 1 +d 2 V 4 =2E+13ΔE−d 1 −d 2 ......Formula (2) This allows the calculation A/ which is the input part of the circuit 11
The dynamic range of the D converter 11a may be narrow, without considering commercial frequency noise.
増幅器１０の出力はt2とt3、t4とt5、t6とt7、t8
とt1の各タイミングの間にＡ／Ｄ変換器１１ａに
よつて演算回路１１に取込まれ、上記４つの加算
値V1〜V4について次式(3)の演算が行われて演算
結果V0がアナログ流量信号１５又はデジタル流
量信号１６として出力される。但しＫはゼロ以外
の定数である。 The outputs of the amplifier 10 are t 2 and t 3 , t 4 and t 5 , t 6 and t 7 , t 8
and t1 , the A/D converter 11a inputs the data into the arithmetic circuit 11, and performs the calculation of the following formula (3) on the above four added values V1 to V4 to obtain the calculation result. V 0 is output as an analog flow signal 15 or a digital flow signal 16 . However, K is a constant other than zero.
V0＝Ｋ（−V1＋3V2−3V3＋V4） ………式(3)
これを説明すると、
V0＝aV1＋bV2＋cV3＋bV4 ………式(4)
なる加算式に上記４つの加算値V1〜V4を代入す
ると、V0は次式(5)となる。 V 0 = K (-V 1 +3V 2 -3V 3 +V 4 ) ......Equation (3) To explain this, we get the addition formula V 0 =aV 1 +bV 2 +cV 3 +bV 4 ......Equation (4) When the above four added values V 1 to V 4 are substituted, V 0 becomes the following equation (5).
V0＝２（ａ−ｃ）V0
＋２（ａ＋ｂ＋ｃ＋ｄ）Ｅ
＋（ａ＋5b＋9c＋13d）ΔE
＋（ａ−ｂ＋ｃ−ｄ）（d1＋d2） ………式(5)
そこで各ノイズ成分をゼロとするには各係数
ａ、ｂ、ｃ、ｄが次式(6)を満足すれば良い。V 0 = 2 (a-c) V 0 + 2 (a + b + c + d) E + (a + 5b + 9c + 13d) ΔE + (a-b + c-d) (d 1 + d 2 ) ......Equation (5) Therefore, each noise component is set to zero. It is only necessary that the coefficients a, b, c, and d satisfy the following equation (6).
ａ−ｃ＝2K≠０
ａ＋ｂ＋ｃ＋ｄ＝０
ａ＋5b＋9c＋13d＝０
ａ−ｂ＋ｃ−ｄ＝０ ………式(6)
この式(6)の解はａ＝−Ｋ、ｂ＝3K、ｃ＝−
3K、ｄ＝Ｋであるから、これらの係数を前式(4)
に代入すれば式(3)となる。したがつて(5)に式(6)を
代入すれば、
V0＝4Kv0
となつてV0は全てのノイズ成分が除去された値
となる。この場合、サンプルホールド回路８，９
の出力が十分には平滑されずリツプル分が残つて
いても式(3)の演算によりこのリツプル分も除去さ
れる。a-c=2K≠0 a+b+c+d=0 a+5b+9c+13d=0 a-b+c-d=0...Equation (6) The solution to this equation (6) is a=-K, b=3K, c=-
3K, d=K, so these coefficients can be expressed in the previous equation (4).
Substituting into , we get equation (3). Therefore, by substituting equation (6) into (5), V 0 =4Kv 0 and V 0 becomes a value from which all noise components have been removed. In this case, sample and hold circuits 8 and 9
Even if the output of is not smoothed sufficiently and some ripple remains, this ripple is also removed by the calculation of equation (3).
なお、上記の説明はサンプリングの処理サイク
ルを第２図ｇ中のt1〜t8とした場合であるが、t2
〜t8〜t1やt3〜t8〜t2などと処理サイクルが異なる
場合でもv2＋v3、v4＋v5、v6＋v7、v8＋v1等の加
算値から商用周波ノイズが除去されており、また
これらの加算値に上述と同様の手順により求めた
係数を掛けて加算すれば全ノイズ成分が除去され
た流量信号が得られる。また、励磁の周波数は第
２図では商用周波数（50Hz、60Hz）の1/4として
あるが、1/6、1/8など1/4以下であれば良い。更
に、直流定電流源１２の代りに励磁電流が変動し
てしまう直流源を用いることができるが、この場
合は、励磁電流を検出してこの値で電極からの信
号を除算する回路を設けて励磁電流の変動による
誤差を取除けば良い。更に、演算回路１１はマイ
クロコンピユータによる構成に限らず通常の回路
構成としても良い。 Note that the above explanation assumes that the sampling processing cycle is t 1 to t 8 in Figure 2g, but t 2
Even if the processing cycles are different from ~ t8 ~ t1 , t3 ~ t8 ~ t2, etc., commercial frequency noise is generated from the added values of v2 + v3 , v4 + v5 , v6 + v7 , v8 + v1 , etc. are removed, and if these added values are multiplied by a coefficient obtained by the same procedure as described above and added, a flow rate signal from which all noise components have been removed can be obtained. Further, although the excitation frequency is set to 1/4 of the commercial frequency (50Hz, 60Hz) in Fig. 2, it may be 1/4 or less, such as 1/6 or 1/8. Furthermore, a DC source whose excitation current fluctuates can be used instead of the DC constant current source 12, but in this case, a circuit is provided to detect the excitation current and divide the signal from the electrode by this value. It is sufficient to remove errors due to fluctuations in excitation current. Furthermore, the arithmetic circuit 11 is not limited to a microcomputer configuration, but may have a normal circuit configuration.
第３図は上述した第１，２図の実施例の変形例
であり、サンプルホールド回路８，９の代りに同
期整流器１７を用いて、サンプリングと商用周波
ノイズ除去用の回路を兼用させてある。同期整流
回路１７のスイツチ素子SW4の開閉は、この場
合、第２図ｇの波形と同波形のタイミング信号１
８によつて制御される。 FIG. 3 is a modification of the embodiment shown in FIGS. 1 and 2 described above, in which a synchronous rectifier 17 is used in place of the sample and hold circuits 8 and 9, and the circuit is used for both sampling and commercial frequency noise removal. . In this case, the switching element SW 4 of the synchronous rectifier circuit 17 is opened and closed using a timing signal 1 having the same waveform as that shown in FIG. 2g.
8.
次に励磁のサイクルとして相互に反対極性の２
つの励磁期間が連続するサイクルを採用した場合
について第４図を参照して説明する。第４図の例
では同図ａに示すように正の励磁期間Ａと負の励
磁期間Ｂとが連続し、従つて２つの休止期間Ｃ、
Ｄも連続している。この例を実現する回路構成は
励磁のためのスイツチ素子の開閉タイミングが異
なり、また演算回路１１における加算の係数が異
なるだけで、第１図や第３図の回路と同じで良
く、従つてサンプリングのタイミングも同じであ
る。そこで第４図ｂに示すタイミングでサンプリ
ングをすれば、電極からの信号の成分である流量
比例信号（同図ｃ）、商用周波ノイズ（同図ｄ）、
電気化学的直流ノイズ（同図ｅ）及び電磁誘導ノ
イズ（同図ｆ）のうち同図ｃ〜ｆの斜線部分が重
畳してサンプリングされる。この場合の処理サイ
クルも第１，２図の例と同じくサンプリングの処
理サイクルを第４図ｂ中のt1〜t8のタイミングと
すれば、各タイミングにおけるサンプル値v′1〜
v′8は次式(7)となる。 Next, as an excitation cycle, two
A case where a cycle in which two consecutive excitation periods are adopted will be described with reference to FIG. 4. In the example of FIG. 4, the positive excitation period A and the negative excitation period B are consecutive, as shown in FIG.
D is also consecutive. The circuit configuration for realizing this example can be the same as the circuit shown in Figures 1 and 3, except that the opening/closing timing of the switch element for excitation is different, and the addition coefficient in the arithmetic circuit 11 is different. The timing is also the same. Therefore, if sampling is performed at the timing shown in Figure 4b, the flow rate proportional signal (Figure 4c), which is a component of the signal from the electrode, the commercial frequency noise (Figure 4D),
Of the electrochemical direct current noise (e in the figure) and the electromagnetic induction noise (f in the figure), the shaded portions c to f in the figure are sampled in a superimposed manner. The processing cycle in this case is the same as the example in FIGS. 1 and 2, and if the sampling processing cycle is set to the timings t 1 to t 8 in FIG. 4b, the sample values at each timing are
v′ 8 becomes the following equation (7).
v′1＝v0＋ｆ−ｅ＋d1
v′2＝v0−ｆ＋Ｅ＋ΔE＋d2
v′3＝−v0＋ｆ＋Ｅ＋2ΔE−2d1
v′4＝−v0−ｆ＋Ｅ＋3ΔE−2d2
v′5＝ｆ＋Ｅ＋4ΔE＋d1
v′6＝−ｆ＋Ｅ＋5ΔE＋d2
v′7＝ｆ＋Ｅ＋6ΔE
v′8＝ｆ＋Ｅ＋7ΔE ………式(7)
但し、式(7)中のv0、ｆ、Ｅ、ΔE、d1、d2の意
味は式(1)と同じである。v′ 1 =v 0 +f−e+d 1 v′ 2 =v 0 −f+E+ΔE+d 2 v′ 3 =−v 0 +f+E+2ΔE−2d 1 v′ 4 =−v 0 −f+E+3ΔE−2d 2 v′ 5 =f+E+4ΔE+d 1 v′ 6 = −f+E+5ΔE+d 2 v′ 7 = f+E+6ΔE v′ 8 = f+E+7ΔE ………Equation (7) However, the meanings of v 0 , f, E, ΔE, d 1 , and d 2 in Equation (7) are as follows from Equation (1). ) is the same as
そこで各サンプリング値v′1〜v′8について２つ
ずつの加算値V′1＝v′1＋v′2、V′2＝v′3＋v′4、V
′3
＝v′5＋v′6、V′4＝v′7＋v′8を予め演算すれば各加
算値には商用周波ノイズがなくなる。このように
して得られた４つの加算値V′1〜V′4は前式(4)によ
り係数ａ、ｂ、ｃ、ｄを掛けて加算されるが、こ
の場合の各係数は式(7)を式(4)に代入して得た次式
(8)のノイズ成分の項を全てゼロとする解を求める
ことにより次式(9)の如く得られる。 Therefore, for each sampling value v' 1 to v' 8 , two added values V' 1 = v' 1 + v' 2 , V' 2 = v' 3 + v' 4 , V
' 3
If =v' 5 +v' 6 and V' 4 =v' 7 +v' 8 are calculated in advance, commercial frequency noise will be eliminated from each added value. The four added values V' 1 to V' 4 obtained in this way are multiplied by the coefficients a, b, c, and d according to the previous formula (4) and added, but each coefficient in this case is calculated by the formula (7). ) obtained by substituting equation (4) into the following equation
By finding a solution in which all noise component terms in (8) are set to zero, the following equation (9) can be obtained.
V0＝２（ａ−ｂ）v0＋２（ａ＋ｂ＋ｃ＋ｄ）Ｅ
＋（ａ＋5b＋9c＋13d）ΔE＋（ａ−2b＋ｃ）（d1
＋d2） ………式(8)
ａ＝2K
ｂ＝−Ｋ
ｃ＝−4K
ｄ＝3K
Ｋ≠０ ………式(9)
この結果、
V0＝Ｋ（2V′1−V′2−4V′3＋3V′4）
の演算を行うこととなり、
V0＝6Kv0
という値のノイズ成分を含まない流量信号が得ら
れる。V 0 =2(a-b)v 0 +2(a+b+c+d)E +(a+5b+9c+13d)ΔE+(a-2b+c)(d 1
+d 2 ) ......Formula (8) a=2K b=-K c=-4K d=3K K≠0 ......Formula (9) As a result, V 0 =K(2V' 1 -V' 2 - 4V′ 3 +3V′ 4 ), and a flow rate signal containing no noise component with a value of V 0 =6Kv 0 is obtained.
なお、サンプリングの処理サイクルがt2〜t8〜
t1などと異なる場合、負の励磁期間Ｂが正の励磁
期間Ａに先行する場合のいずれにおいても、式(4)
の演算前に商用周波ノイズが除去され、式(4)の各
係数は同様の手順順により求めることができる。 Note that the sampling processing cycle is from t 2 to t 8 to
In any case where the negative excitation period B precedes the positive excitation period A, Equation (4)
Commercial frequency noise is removed before the calculation of , and each coefficient in equation (4) can be obtained using the same procedure.
以上詳細に説明したように、本発明の電磁流量
計ではサンプリングの直後に商用周波ノイズが除
去されるので演算処理に必要とされる次段の増幅
器やＡ／Ｄ変換器のダイナミツクレンジが狭くて
済み、低コスト化を図れる。もちろんこの電磁流
量計は電磁誘導ノイズ及び電気化学直流ノイズを
簡単な構成で除去でき、しかも演算に用いるサン
プリング値には電磁誘導ノイズが含まれていても
かまわないのでサンプリングは電磁誘導ノイズが
十分に減衰しないうちに行つても良いこととな
り、励磁のサイクルを短くできて出力応答特性が
早くなる。なお、本発明は電極が一対だけでなく
３個以上の電磁流量計にも適用できることは言う
までもない。 As explained in detail above, in the electromagnetic flowmeter of the present invention, commercial frequency noise is removed immediately after sampling, so the dynamic range of the next stage amplifier and A/D converter required for calculation processing is narrowed. This allows for cost reduction. Of course, this electromagnetic flowmeter can remove electromagnetic induction noise and electrochemical direct current noise with a simple configuration, and it does not matter if the sampled values used for calculations contain electromagnetic induction noise, so the sampling is sufficient to eliminate electromagnetic induction noise. It is possible to do this before attenuation occurs, and the excitation cycle can be shortened, resulting in faster output response characteristics. It goes without saying that the present invention can be applied not only to an electromagnetic flowmeter having one pair of electrodes but also to an electromagnetic flowmeter having three or more electrodes.
第１図は本発明の一実施例を示すブロツク構成
図、第２図ａ〜ｋは第１図中各部の動作を説明す
るための波形図、第３図は第１図の例の変形例を
示すブロツク構成図、第４図ａ〜ｆは他の実施例
を説明するための波形図である。
図面中、１は励磁コイル、２は絶縁導管、３
ａ，３ｂは電極、７は演算制御回路、８，９はサ
ンプルホールド回路、１１は演算回路、１７は同
期整流回路である。
FIG. 1 is a block configuration diagram showing one embodiment of the present invention, FIGS. 2 a to k are waveform diagrams for explaining the operation of each part in FIG. 1, and FIG. 3 is a modification of the example in FIG. 1. FIGS. 4a to 4f are waveform diagrams for explaining other embodiments. In the drawing, 1 is an excitation coil, 2 is an insulated conduit, and 3
Reference numerals a and 3b are electrodes, 7 is an arithmetic control circuit, 8 and 9 are sample and hold circuits, 11 is an arithmetic circuit, and 17 is a synchronous rectifier circuit.
Claims (1)
等時間長の期間であつて２つの休止期間と相互に
反対極性の２つの励磁期間との計４期間を所定の
順序で組合せて励磁を繰返す励磁回路と、電極か
らの信号をサンプリングしサンプル値を演算して
商用周波ノイズ、電気化学的直流ノイズ及び磁束
密度変化による電磁誘導ノイズを低減した流量信
号を出力する演算制御回路であり、上記電極から
の信号を商用周波数に同期して上記４期間の夫々
で偶数回サンプリングするサンプリング回路、こ
のサンプリング回路からの信号を入力しサンプル
値を偶数個ずつ加算して商用周波ノイズを相殺す
る加算回路、並びにこの加算回路からの信号を入
力し各加算値夫々に係数を掛けて加算する演算に
より上記流量信号を出力し、各係数は上記４期間
の組合せ順序と上記加算回路での加算組合せとで
定まり演算により上記電気化学的直流ノイズ及び
電磁誘導ノイズを夫々相殺する数値とした演算回
路からなる上記演算制御回路とを具備したことを
特徴とする電磁流量計。 ２ 上記の１サイクルが相互に反対極性の励磁期
間の間に休止期間が１つずつ介在する組合せであ
ることを特徴とする特許請求の範囲第１項記載の
電磁流量計。 ３ 上記の１サイクルが相互に反対極性の２つの
励磁期間が連続する組合せであることを特徴とす
る特許請求の範囲第１項記載の電磁流量計。[Claims] 1. In an electromagnetic flowmeter with rectangular wave excitation, a total of four periods, two rest periods and two excitation periods of opposite polarity, both of which are equal in length, are combined in a predetermined order. An excitation circuit that repeats excitation by the electrode, and a calculation control circuit that samples the signal from the electrode, calculates the sample value, and outputs a flow signal with reduced commercial frequency noise, electrochemical DC noise, and electromagnetic induction noise due to changes in magnetic flux density. Yes, there is a sampling circuit that samples the signal from the electrodes an even number of times in each of the four periods in synchronization with the commercial frequency, and the signal from this sampling circuit is input and the sample values are added in even numbers to cancel the commercial frequency noise. The above flow rate signal is outputted by inputting the signal from the adder circuit and the signal from this adder circuit, multiplying each added value by a coefficient, and adding them, and each coefficient is calculated based on the combination order of the above four periods and the addition in the above adder circuit. 1. An electromagnetic flowmeter comprising: an arithmetic control circuit which is determined by a combination of arithmetic and arithmetic values to cancel each of the electrochemical direct current noise and the electromagnetic induction noise. 2. The electromagnetic flowmeter according to claim 1, wherein the one cycle is a combination in which one rest period is interposed between excitation periods of opposite polarity. 3. The electromagnetic flowmeter according to claim 1, wherein said one cycle is a combination of two consecutive excitation periods of mutually opposite polarity.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7136481A JPH0228807B2 (en) | 1981-05-14 | 1981-05-14 | DENJIRYURYOKEI |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7136481A JPH0228807B2 (en) | 1981-05-14 | 1981-05-14 | DENJIRYURYOKEI |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57187620A JPS57187620A (en) | 1982-11-18 |
| JPH0228807B2 true JPH0228807B2 (en) | 1990-06-26 |
Family
ID=13458364
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7136481A Expired - Lifetime JPH0228807B2 (en) | 1981-05-14 | 1981-05-14 | DENJIRYURYOKEI |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0228807B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS58115323A (en) * | 1981-12-29 | 1983-07-09 | Yokogawa Hokushin Electric Corp | Electromagentic flowmeter |
-
1981
- 1981-05-14 JP JP7136481A patent/JPH0228807B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57187620A (en) | 1982-11-18 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4210022A (en) | Method for the inductive measurement of fluid flow | |
| US6845330B2 (en) | Electromagnetic flowmeter | |
| KR100186888B1 (en) | Electromagnetic flowmeter | |
| EP0629843B1 (en) | Electromagnetic flowmeter and method for electromagnetically measuring flow rate | |
| US4644799A (en) | Electromagnetic flow meter | |
| JPH0554886B2 (en) | ||
| EP0322802B1 (en) | Watthour meter or wattmeter comprising hall sensors | |
| JP2661933B2 (en) | Circuit for measuring the DC component of the current flowing through the primary winding of the output transformer of the inverter | |
| US5808208A (en) | Inductive flow meter | |
| JPH0228807B2 (en) | DENJIRYURYOKEI | |
| JPH0735788A (en) | Power-computing device | |
| JPS60102567A (en) | Method and device for compensating electric signal nonlinearly changing with time | |
| US4733191A (en) | Circuit for changing a periodic intelligence signal into a direct-current signal | |
| JPH0258569B2 (en) | ||
| JP3197309B2 (en) | Electrical measuring device | |
| EP0228809B1 (en) | Electromagnetic flowmeters | |
| JPH0477850B2 (en) | ||
| JPH0228806B2 (en) | DENJIRYURYOKEI | |
| JPS5965771A (en) | Current detecting circuit | |
| JP2017142068A (en) | Current sensor and filtering method thereof | |
| JPH0212018A (en) | Electromagnetic flow meter | |
| JPS58115323A (en) | Electromagentic flowmeter | |
| SU1739199A1 (en) | Device for information recording | |
| SU1086495A1 (en) | Error compensator of current transformer | |
| JPH04339217A (en) | Electromagnetic flowmeter |