JP5522473B2 - Electromagnetic flow meter - Google Patents
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本発明は、高周波励磁信号と低周波励磁信号による磁界を測定管内を流れる流体に与え、前記測定管内に設けられた一対の検出電極に発生する検出信号に基づき前記流体の流量を測定する電磁流量計における付着診断機能に関するものである。 The present invention provides an electromagnetic flow rate that applies a magnetic field generated by a high-frequency excitation signal and a low-frequency excitation signal to a fluid flowing in a measurement tube, and measures the flow rate of the fluid based on detection signals generated in a pair of detection electrodes provided in the measurement tube. This relates to the adhesion diagnosis function in the meter.
図6は、付着診断機能を有する電磁流量計の構成例を示す機能ブロック図である。測定管1内に電極21,22設けられている。管路を流れる流体は励磁回路4から励磁コイル31,32を介して励磁され、電極21,22に流量に比例した検出電圧e1,e2を誘起する。 FIG. 6 is a functional block diagram showing a configuration example of an electromagnetic flow meter having an adhesion diagnosis function. Electrodes 21 and 22 are provided in the measurement tube 1. The fluid flowing through the pipe line is excited from the excitation circuit 4 via the excitation coils 31 and 32, and induces detection voltages e1 and e2 proportional to the flow rate to the electrodes 21 and 22, respectively.
検出電圧e1,e2は、バッファ51,52を経由して差動増幅回路6で差動演算され、可変ゲイン回路7でゲイン調節された後、A/D変換器8でデジタル変換され、CPU9でデータ処理され、流量信号が演算される。 The detection voltages e1 and e2 are differentially calculated by the differential amplifier circuit 6 via the buffers 51 and 52, adjusted in gain by the variable gain circuit 7, and then digitally converted by the A / D converter 8, and the CPU 9 Data processing is performed, and a flow rate signal is calculated.
付着診断機能は、付着診断を実施するための付着信号付与手段10から電極21,22へ付着信号i1,i2を印加し、付着抵抗r1,r2に発生する電圧を電極21,22より検出する。 The adhesion diagnosis function applies adhesion signals i1 and i2 to the electrodes 21 and 22 from the adhesion signal applying means 10 for performing the adhesion diagnosis, and detects voltages generated at the adhesion resistances r1 and r2 from the electrodes 21 and 22.
従って、バッファ51,52は、励磁により電極間に誘起される流量信号と付着に関する信号が重畳された電圧を受信する。CPU9は、重畳された検出電圧から信号処理によって、流量信号と付着信号を分離処理して出力する。付着診断機能を備えた電磁流量計については、特許文献1に基本的な技術開示がある。 Accordingly, the buffers 51 and 52 receive a voltage in which a flow rate signal induced between the electrodes by excitation and a signal related to adhesion are superimposed. The CPU 9 separates and outputs the flow rate signal and the adhesion signal by signal processing from the superimposed detection voltage. Patent Document 1 discloses a basic technical disclosure of an electromagnetic flow meter having an adhesion diagnosis function.
電磁流量計では、電極間に励磁に伴う微分ノイズが必然的に発生する。流量信号については、微分ノイズの少ないタイミングでのサンプリングや、CPU9における演算で微分ノイズを除去して流量信号を抽出して出力する。 In an electromagnetic flow meter, differential noise accompanying excitation is inevitably generated between electrodes. As for the flow rate signal, the differential signal is removed by sampling at a timing with little differential noise or calculation in the CPU 9 to extract and output the flow rate signal.
また付着信号については、流量信号と干渉しないような付着信号の波形、印加タイミングを励磁のタイミングと同期させる等の処理を追加して付着信号を抽出しなければならない。 For the adhesion signal, it is necessary to extract the adhesion signal by adding processing such as the waveform of the adhesion signal that does not interfere with the flow rate signal and the application timing being synchronized with the excitation timing.
このため、付着診断機能を持たない場合に比べ、微分ノイズについての条件、付着診断信号印加の条件が厳しくなり、励磁回路の設計が困難になったり、消費電力が増大することがある。 For this reason, as compared with the case where the adhesion diagnosis function is not provided, conditions for differential noise and conditions for application of an adhesion diagnosis signal become strict, and it may be difficult to design an excitation circuit or increase power consumption.
図7は、図6の信号処理手順を示すフローチャートである。ステップS1で処理ルーチンが開始されると、ステップS2の励磁とステップS3の付加信号印加が実行される。ステップS4で検出される流量信号とステップS5で検出される微分ノイズは付着信号と重畳され、ステップS6で増幅される。 FIG. 7 is a flowchart showing the signal processing procedure of FIG. When the processing routine is started in step S1, excitation in step S2 and application of an additional signal in step S3 are executed. The flow rate signal detected in step S4 and the differential noise detected in step S5 are superimposed on the adhesion signal and amplified in step S6.
増幅された信号は、ステップS7でAD変換され、ステップS8のCPU処理演算で流量信号と付着信号が分離され、ステップS9で流量信号を出力すると共に、ステップS10で付着信号を出力し、ステップS11で処理ルーチンを終了する。 The amplified signal is AD converted in step S7, the flow rate signal and the adhesion signal are separated by the CPU processing calculation in step S8, the flow rate signal is output in step S9, the adhesion signal is output in step S10, and step S11. The processing routine is finished.
高周波励磁信号と低周波励磁信号による磁界を測定管内を流れる流体に与える、いわゆる2周波励磁電磁流量計における付着信号分離の手法についても特許文献1及び特許文献2に技術開示がある。 Patent Document 1 and Patent Document 2 also disclose a technique for separating adhesion signals in a so-called two-frequency excitation electromagnetic flowmeter that applies a magnetic field generated by a high-frequency excitation signal and a low-frequency excitation signal to a fluid flowing in a measurement tube.
特許文献1及び特許文献2に技術開示されている2周波励磁電磁流量計における付着信号分離の手法は、特許文献2の段落[0063]に「励磁及び流量信号(励磁電流波形)と診断信号(診断信号波形)との同期をとる。そして、診断信号にかかる診断タイミング(診断信号波形)の周波数を、2つの周波数より構成される励磁電流波形における高周波数(H)と低周波数(L)の中間の周波数にする。そして、診断信号の検出即ち診断信号サンプリングのタイミングを低周波(L)の偶数倍とするとともに、高周波(H)の偶数分の1とし、診断信号のサンプリングは、微分ノイズが充分に減少する、低周波(L)の周期の後半部で行う。」の記載がある。 The technique for separating the adhesion signal in the two-frequency excitation electromagnetic flowmeter that is technically disclosed in Patent Document 1 and Patent Document 2 is described in paragraph [0063] of Patent Document 2 as “Excitation and flow signal (excitation current waveform) and diagnostic signal ( The frequency of the diagnosis timing (diagnostic signal waveform) applied to the diagnostic signal is set to the high frequency (H) and low frequency (L) in the excitation current waveform composed of two frequencies. The timing of the detection of the diagnostic signal, that is, the sampling of the diagnostic signal is an even multiple of the low frequency (L) and the even number of the high frequency (H). Is performed in the latter half of the low frequency (L) period. ”.
このような従来手法では、付着信号が微分ノイズに対して十分大きくない場合には、微分ノイズの影響により付着物の抵抗値を高精度に測定することができない。更に。診断信号の周波数を、2つの励磁周波数より構成される励磁電流波形における高周波数(H)と低周波数(L)の中間の周波数に選定する等、回路構成が煩雑である。 In such a conventional method, when the adhesion signal is not sufficiently large with respect to the differential noise, the resistance value of the deposit cannot be measured with high accuracy due to the influence of the differential noise. Furthermore. The circuit configuration is complicated, such as selecting the frequency of the diagnostic signal as a frequency intermediate between the high frequency (H) and the low frequency (L) in the excitation current waveform composed of two excitation frequencies.
本発明の目的は、2周波励磁を行う電磁流量計において、微分ノイズの影響を効果的に除去し、高精度で付着信号を抽出可能な電磁流量計を実現することにある。 An object of the present invention is to realize an electromagnetic flowmeter capable of effectively removing the influence of differential noise and extracting an adhesion signal with high accuracy in an electromagnetic flowmeter performing two-frequency excitation.
このような課題を達成するために、本発明は次の通りの構成になっている。
(1)高周波励磁信号と低周波励磁信号による磁界を測定管内を流れる流体に与え、前記測定管内に設けられた一対の検出電極に発生する検出信号に基づき前記流体の流量を測定する電磁流量計において、
前記測定管内に設けられ前記流量測定時の基準電位となるアース電極と、前記検出電極に接続され、前記高周波励磁信号に同期し、その整数倍の周波数を持つ付着物の診断のための交流信号を発生する付着物信号付与手段と、
前記低周波励磁信号の極性反転タイミングより前の前記交流信号と同期する複数の連続した半周期でサンプルした前記検出電極間のサンプル電圧信号に基づいて前記付着物の量を演算する付着物診断部と、
を備えることを特徴とする電磁流量計。
In order to achieve such a subject, the present invention has the following configuration.
(1) An electromagnetic flowmeter that applies a magnetic field generated by a high-frequency excitation signal and a low-frequency excitation signal to a fluid flowing in a measurement tube and measures the flow rate of the fluid based on detection signals generated at a pair of detection electrodes provided in the measurement tube. In
An AC signal for diagnosing deposits having a frequency that is an integral multiple of the ground electrode provided in the measuring tube and connected to the detection electrode and serving as a reference potential at the time of the flow rate measurement, synchronized with the high-frequency excitation signal A deposit signal giving means for generating
A deposit diagnostic unit that calculates the amount of deposit based on sample voltage signals between the detection electrodes sampled in a plurality of consecutive half cycles synchronized with the AC signal before the polarity inversion timing of the low frequency excitation signal When,
An electromagnetic flow meter comprising:
(2)前記サンプル電圧信号は、前記低周波励磁信号の微分ノイズ、前記高周波励磁信号の微分ノイズ、前記流体の流量信号、付着信号であることを特徴とする(1)に記載の電磁流量計。 (2) The electromagnetic flow meter according to (1), wherein the sample voltage signal is a differential noise of the low frequency excitation signal, a differential noise of the high frequency excitation signal, a flow rate signal of the fluid, or an adhesion signal. .
(3)前記付着物診断部は、前記サンプル電圧信号に対して係数を与える係数付加手段を備えることを特徴とする(1)または(2)に記載の電磁流量計。 (3) The electromagnetic flowmeter according to (1) or (2), wherein the deposit diagnostic unit includes coefficient adding means for giving a coefficient to the sample voltage signal.
(4)前記付着物診断部は、係数が付加された前記サンプル電圧信号を加減算し、付着物信号を抽出する付着演算手段を備えることを特徴とする(3)に記載の電磁流量計。 (4) The electromagnetic flowmeter according to (3), wherein the deposit diagnostic unit includes an adhesion calculation unit that adds and subtracts the sample voltage signal to which a coefficient is added to extract the deposit signal.
(5)前記複数の連続した半周期のサンプル個数は3個であることを特徴とする(1)乃至(4)のいずれかに記載の電磁流量計。 (5) The electromagnetic flowmeter according to any one of (1) to (4), wherein the number of samples in the plurality of consecutive half cycles is three.
(6)前記複数の連続した半周期のサンプル個数は4個であることを特徴とする(1)乃至(4)のいずれかに記載の電磁流量計。 (6) The electromagnetic flowmeter according to any one of (1) to (4), wherein the number of samples in the plurality of consecutive half cycles is four.
(7)前記複数の連続した半周期のサンプル個数は5個であることを特徴とする(1)乃至(4)のいずれかに記載の電磁流量計。 (7) The electromagnetic flowmeter according to any one of (1) to (4), wherein the number of samples in the plurality of consecutive half cycles is five.
本発明によれば、流量信号抽出のためサンプルされた電極信号から演算により電磁流量計に本質的に付随するノイズ成分(ランプノイズ:電極に生ずる比較的長時間にわたって変化する直流電位変化で電磁流量計に固有のノイズ成分、励磁磁束の時間変化(δB/δt)で発生する微分ノイズ)及び流量信号とは独立した付着信号を得ることができる。 According to the present invention, a noise component (ramp noise: a direct current potential change that occurs in an electrode for a relatively long time, which is inherently associated with an electromagnetic flowmeter by calculation from a sampled electrode signal for extraction of a flow rate signal, is detected. It is possible to obtain an adhesion signal independent of the noise component inherent to the meter, the differential noise generated by the time variation of the excitation magnetic flux (ΔB / Δt), and the flow rate signal.
以下本発明を、図面を用いて詳細に説明する。図1は、本発明を適用した電磁流量計の一実施例を示す機能ブロック図である。図6で説明した従来構成と同一要素には同一符号を付して説明を省略する。 Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a functional block diagram showing an embodiment of an electromagnetic flow meter to which the present invention is applied. The same elements as those in the conventional configuration described with reference to FIG.
図6の従来構成に追加される特徴部は、CPU9内のデータ処理構成にある。CPU9は従来機能と共通する流量演算部91と、本発明の適用対象である付着診断部100を具備している。 A feature added to the conventional configuration of FIG. 6 is a data processing configuration in the CPU 9. The CPU 9 includes a flow rate calculation unit 91 that is common to conventional functions, and an adhesion diagnosis unit 100 to which the present invention is applied.
付着診断部100は、サンプルデータに係数を付する係数付加手段101、係数が付加されたデータを加減算して付着信号を高精度で抽出する付着演算手段、演算結果を評価する判定手段103で構成されている。更に、付着信号付与手段10には、高周波励磁信号に同期し、その整数倍の周波数を持つ付着物の診断のための交流信号を発生させる制御信号mがCPU9より与えられている。 The adhesion diagnosis unit 100 includes a coefficient adding means 101 for adding a coefficient to sample data, an adhesion calculating means for adding and subtracting the data to which the coefficient is added and extracting an adhesion signal with high accuracy, and a determining means 103 for evaluating the calculation result. Has been. Further, the control signal m for generating an AC signal for diagnosis of the deposit having a frequency that is an integral multiple of the high frequency excitation signal is supplied from the CPU 9 to the adhesion signal applying means 10.
図2は、本発明を適用した電磁流量計の信号処理手順を示すフローチャートである。図7に示したフローチャートに追加されるステップは、S12乃至S15である。ステップS12は、ステップS8で分離された付着信号演算ルートのスタートステップである。ステップS13ではサンプルデータに対して係数が付加され、ステップS14で係数が付加されたデータの加減算演算で付着信号を抽出し、ステップS15で評価判定され、ステップS11で付着信号処理のルーチンを終了する。 FIG. 2 is a flowchart showing a signal processing procedure of the electromagnetic flow meter to which the present invention is applied. Steps added to the flowchart shown in FIG. 7 are S12 to S15. Step S12 is a start step of the adhesion signal calculation route separated in step S8. In step S13, a coefficient is added to the sample data, an adhesion signal is extracted by addition / subtraction of the data to which the coefficient is added in step S14, evaluation is determined in step S15, and the adhesion signal processing routine is terminated in step S11. .
図3、図4、図5は、本発明を適用した電磁流量計の動作を説明するタイムチャートである。本発明では、低周波励磁信号の極性反転タイミングより前の付着信号と同期する複数の連続した半周期でサンプルした検出電極間のサンプル電圧信号に係数を付与して加減算するが、図3では連続3個、図4では連続4個、図5では連続5個のサンプルデータを利用する。これら実施形態では、付着信号の周波数を高周波励磁信号の2倍の周波数としている。 3, 4 and 5 are time charts for explaining the operation of the electromagnetic flow meter to which the present invention is applied. In the present invention, a coefficient is given to the sample voltage signal between the detection electrodes sampled in a plurality of consecutive half cycles synchronized with the adhesion signal before the polarity inversion timing of the low frequency excitation signal, and addition and subtraction are performed in FIG. Three, four consecutive sample data in FIG. 4, and five consecutive sample data in FIG. 5 are used. In these embodiments, the frequency of the adhesion signal is twice that of the high frequency excitation signal.
図3、図4、図5のタイムチャートにおいて、(A)乃至(F)の波形は以下を示す。
(A)励磁波形:2周波励磁の励磁波形
(B)ランプノイズ:電極に生ずる比較的長時間にわたって変化する直流電位変化で電磁流量計に固有のノイズ成分
(C)L側微分ノイズ:低周波の励磁磁束変動によって生ずる低周波微分ノイズ成分
(D)H側微分ノイズ:高周波の励磁磁束変動によって生ずる高周波微分ノイズ成分
(E)流量信号
(F)付着信号診断のため付加した付着信号
In the time charts of FIGS. 3, 4, and 5, the waveforms (A) to (F) indicate the following.
(A) Excitation waveform: Excitation waveform of 2-frequency excitation (B) Lamp noise: Noise component inherent to the electromagnetic flowmeter due to a change in DC potential that occurs at the electrode over a relatively long time (C) L side differential noise: Low frequency Low frequency differential noise component (D) H side differential noise caused by fluctuations in excitation magnetic flux: High frequency differential noise component (E) flow rate signal (F) caused by high frequency excitation magnetic flux fluctuations Adhesion signal added for diagnosis of adhesion signal
図3の実施形態の信号処理を説明する。(A)乃至(F)示した各波形から、(B)ランプノイズ、(C)L側微分ノイズ、(D)H側微分ノイズを除去して、(E)流量信号及び(F)付着信号を分離取り出すことが必要となる。 The signal processing of the embodiment of FIG. 3 will be described. (B) Lamp noise, (C) L side differential noise, (D) H side differential noise are removed from each waveform shown in (A) to (F), and (E) flow rate signal and (F) adhesion signal are removed. Need to be separated and removed.
本発明では、(F)付着信号の分離取り出しについての演算を提案するものであり、
(E)流量信号を分離する技術については、従来の2周波励磁の演算によるもので、本発明の目的とするところではない。
In the present invention, (F) an operation for separating and extracting the adhesion signal is proposed,
(E) The technique for separating the flow rate signal is based on the conventional two-frequency excitation calculation and is not the object of the present invention.
図3で、(C)L側微分ノイズが減少する(a)〜(c)および(d)〜(f)のタイミングで(B)〜(F)が重畳された電極電圧信号をサンプルする。各タイミングでサンプルれた信号成分を図3の下部に、(a)=… etc.で示している。 In FIG. 3, (C) the electrode voltage signal on which (B) to (F) are superimposed is sampled at the timings (a) to (c) and (d) to (f) at which the L-side differential noise decreases. The signal components sampled at each timing are indicated by (a) =... Etc. at the bottom of FIG.
(B)ランプノイズを除去するため、(a)〜(c)および(d)〜(f)の各サンプル値に対し、(−1,―2,1)の重み付け係数を付与した上で加算すると、
(a)-2*(b)-(c)=(n+9N+L9+H1+S-A)-2*(n+10N+L10-H0+A)+(n+11N+L11-H1-A)
=+L9-2L10+L11+2H0+S-4A
(d)-2*(e)-(f)=(n+21N-L9-H1-S-A)-2*(n+22N-L10+H0+A)+(n+23N-L11+H1-A)
=-L9+2L10-L11-2H0-S-4A
((a)-2*(b)-(c))+((d)-2*(e)-(f))=(+L9-2L10+L11+2H0+S-4A)+(-L9+2L10-L11-2H0-S-4A)
=-8A (式1)
となる。
(B) In order to remove lamp noise, each sample value of (a) to (c) and (d) to (f) is added after adding a weighting coefficient of (-1, -2, 1). Then
(a) -2 * (b)-(c) = (n + 9N + L9 + H1 + SA) -2 * (n + 10N + L10-H0 + A) + (n + 11N + L11-H1-A )
= + L9-2L10 + L11 + 2H0 + S-4A
(d) -2 * (e)-(f) = (n + 21N-L9-H1-SA) -2 * (n + 22N-L10 + H0 + A) + (n + 23N-L11 + H1-A )
= -L9 + 2L10-L11-2H0-S-4A
((a) -2 * (b)-(c)) + ((d) -2 * (e)-(f)) = (+ L9-2L10 + L11 + 2H0 + S-4A) + (-L9 + 2L10-L11-2H0-S-4A)
= -8A (Formula 1)
It becomes.
また、次の低周波の周期でサンプルされる(g)〜(l)の信号についても同様の結果を得る。
即ち、付着信号を各ノイズ成分および流量信号から分離して、付着信号のみを大きさ-8Aで抽出して付着診断を実施できる。
Similar results are obtained for the signals (g) to (l) sampled at the next low frequency period.
That is, the adhesion signal can be separated from each noise component and the flow rate signal, and the adhesion diagnosis can be performed by extracting only the adhesion signal with a magnitude of -8A.
この実施形態の場合、(B)ランプノイズの変化が低周波周期にたいし小さいとみなせる場合には、演算を簡易化して、(b),(c)および(e),(f)のタイミングの信号のみを用いた演算でも付着信号を抽出できる。この場合(b),(c),(e),(f)に対し(1,-1)の係数を付して加算する。
(b)-(c)=(n+10N+L10-H0+A)-(n+11N+L11-H1-A)
=-N+L10-L11-H0+H1+2A
(e)-(f)=(n+24N-L10+H0+A)-(n+25N-L11+H1-A)
=-N-L10+L11+H0-H1+2A
((b)-(c))+((e)-(f))=(-N+L10-L11-H0+H1+2A)+(-N-L10+L11+H0-H1+2A)
=-2N+2A=+2A (2N≪2A)
となり、付着信号2Aを抽出できる。
In the case of this embodiment, when (B) the change in lamp noise can be regarded as being small with respect to the low frequency period, the calculation is simplified and the timings (b), (c) and (e), (f) are simplified. The adhesion signal can be extracted even by calculation using only the above signal. In this case, a coefficient (1, -1) is added to (b), (c), (e), and (f) and added.
(b)-(c) = (n + 10N + L10-H0 + A)-(n + 11N + L11-H1-A)
= -N + L10-L11-H0 + H1 + 2A
(e)-(f) = (n + 24N-L10 + H0 + A)-(n + 25N-L11 + H1-A)
= -N-L10 + L11 + H0-H1 + 2A
((B)-(c)) + ((e)-(f)) = (-N + L10-L11-H0 + H1 + 2A) + (-N-L10 + L11 + H0-H1 + 2A)
= -2N + 2A = + 2A (2N << 2A)
Thus, the adhesion signal 2A can be extracted.
3個のサンプル値を使用する図3の処理方式に比べて付着診断に使用するサンプル値の数が少なく、AD変換するための消費電力を少なくできるので、2線式電磁流量計等への適用が考えられる。 Compared to the processing method shown in FIG. 3 that uses three sample values, the number of sample values used for adhesion diagnosis is small, and power consumption for AD conversion can be reduced. Can be considered.
付着診断のために使用するサンプル値の数を増やすことにより、他の演算による付着信号の抽出が可能になる。図3の実施形態では、H成分微分ノイズをタイミング(a),(b),(c)および(d),(e),(f)でサンプルして、すべてのノイズを除去するため、微分ノイズの大きなタイミング(b),(e)に係数2を乗じて演算している。 By increasing the number of sample values used for adhesion diagnosis, it is possible to extract adhesion signals by other calculations. In the embodiment of FIG. 3, the H component differential noise is sampled at timings (a), (b), (c) and (d), (e), (f) to eliminate all noise. Calculation is performed by multiplying the timing (b), (e) with a large noise by a factor of 2.
このため、タイミング(b),(e)のサンプル値は他のサンプル値と比べ2倍の重みが要求される。他のサンプル値と同じ重み付けで信号処理する手法を図4により説明する。この実施形態では、正負の低周波励磁周期の最後のタイミングより4個前までのサンプル値を用いて演算する。 For this reason, the sample values at the timings (b) and (e) are required to be twice as heavy as the other sample values. A method of performing signal processing with the same weight as other sample values will be described with reference to FIG. In this embodiment, calculation is performed using up to four sample values before the last timing of the positive and negative low-frequency excitation periods.
この実施形態では、演算処理のための消費電力が増加するが、L側微分ノイズ、H側微分ノイズに対する係数付与の条件が緩和し、より正確な付着信号の抽出が可能となる。 In this embodiment, although the power consumption for the arithmetic processing increases, the condition for applying the coefficients to the L-side differential noise and the H-side differential noise is relaxed, and a more accurate adhesion signal can be extracted.
タイミング(a),(b),(c),(d)および(e),(f),(g),(h)でサンプリングされた信号に、(+1,―1,+1,―1)の係数を付与し、加算演算する。タイミングでの(a),(b),(c),(d)演算結果は、
(式2)で表記される。
Signals sampled at timings (a), (b), (c), (d) and (e), (f), (g), (h) are added to (+1, -1, +1, -1) Is added and the addition operation is performed. (A), (b), (c), (d) calculation results at the timing are
It is expressed by (Formula 2).
タイミングの(e),(f),(g),(h)演算結果は、(式3)で表記される。 The timing (e), (f), (g), and (h) calculation results are expressed by (Expression 3).
であり、(式2)+(式3)=8Aとなり、1回の演算周期で図3の実施形態と同一の抽出結果を得ることができる。 (Expression 2) + (Expression 3) = 8A, and the same extraction result as that of the embodiment of FIG. 3 can be obtained in one calculation cycle.
1回の演算周期でより大きな付着信号を得る手法として、図5の実施形態を説明する。この実施形態では、正負の低周波励磁周期の最後のタイミングより5個前までのサンプル値を用いて演算する。付着診断に使用するサンプル値の増加により、診断の精度を上げることができる。 The embodiment of FIG. 5 will be described as a technique for obtaining a larger adhesion signal in one calculation cycle. In this embodiment, calculation is performed using up to five sample values before the last timing of the positive and negative low frequency excitation periods. The accuracy of the diagnosis can be increased by increasing the sample value used for the adhesion diagnosis.
タイミング(a),(b),(c),(d),(e)および(f),(g),(h),(i),(j)でサンプルされた信号に、(+1,―2,+2,―2,+1)の係数を付与し、加算演算する。タイミング(a),(b),
(c),(d),(e)の演算結果は、(式4)で表記される。
Signals sampled at timings (a), (b), (c), (d), (e) and (f), (g), (h), (i), (j) are (+1, -2, +2, -2, +1) coefficients are added and the addition operation is performed. Timing (a), (b),
The calculation results of (c), (d), and (e) are expressed by (Expression 4).
タイミング(f)(g)(h)(i)(j)の演算結果は、(式5)で表記される。 The calculation result of timing (f) (g) (h) (i) (j) is expressed by (Formula 5).
(式4)+(式5)の演算結果は、(式6)で表記される。 The calculation result of (Expression 4) + (Expression 5) is expressed by (Expression 6).
この実施形態では、図3、図4の実施形態の感度8Aに対して2倍の感度16Aで付着信号を抽出することが可能である。 In this embodiment, it is possible to extract the adhesion signal with a sensitivity 16A that is twice the sensitivity 8A of the embodiment of FIGS.
1 測定管
21,22 電極
31,32 励磁コイル
4 励磁回路
51,52 バッファ
6 差動増幅回路
7 可変ゲイン回路
8 A/D変換器
9 CPU
10 付着信号付与手段
91 流量演算部
100 付着診断部
101 係数付加手段
102 付着演算手段
103 判定手段
DESCRIPTION OF SYMBOLS 1 Measuring tube 21,22 Electrode 31,32 Excitation coil 4 Excitation circuit 51,52 Buffer 6 Differential amplification circuit 7 Variable gain circuit 8 A / D converter 9 CPU
DESCRIPTION OF SYMBOLS 10 Adhesion signal provision means 91 Flow volume calculating part 100 Adhesion diagnostic part 101 Coefficient addition means 102 Adhesion calculating means 103 Determination means
Claims (7)
前記測定管内に設けられ前記流量測定時の基準電位となるアース電極と、前記検出電極に接続され、前記高周波励磁信号に同期し、その整数倍の周波数を持つ付着物の診断のための交流信号を発生する付着物信号付与手段と、
前記低周波励磁信号の極性反転タイミングより前の前記交流信号と同期する複数の連続した半周期でサンプルした前記検出電極間のサンプル電圧信号に基づいて前記付着物の量を演算する付着物診断部と、
を備えることを特徴とする電磁流量計。 In an electromagnetic flowmeter that applies a magnetic field by a high-frequency excitation signal and a low-frequency excitation signal to a fluid flowing in a measurement tube and measures a flow rate of the fluid based on a detection signal generated in a pair of detection electrodes provided in the measurement tube,
An AC signal for diagnosing deposits having a frequency that is an integral multiple of the ground electrode provided in the measuring tube and connected to the detection electrode and serving as a reference potential at the time of the flow rate measurement, synchronized with the high-frequency excitation signal A deposit signal giving means for generating
A deposit diagnostic unit that calculates the amount of deposit based on sample voltage signals between the detection electrodes sampled in a plurality of consecutive half cycles synchronized with the AC signal before the polarity inversion timing of the low frequency excitation signal When,
An electromagnetic flow meter comprising:
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