JPS586412A - Electromagnetic flow meter - Google Patents

Abstract

PURPOSE:To compensate the span fluctuation with high accuracy over a wide range of the exciting frequency and without using any RC delay circuit, by using a microcomputer for the signal process and compensating the span fluctuation with an operation. CONSTITUTION:The span compensation degree alpha due to the type of a transmitter based on its caliber, etc. and the exciting frequency is obtained previously and stored in an ROM12. Then a CPU11 reads the degree alpha out of the ROM12 based on the designation of selection for the caliber of the transmitter via a setting switch 16 and the frequency of a power supply 8 which is measured by a frequency counter 17. Thus the correct flow rate value is obtained from V0= Vs/alpha to the measured flow rate value Vs. At the same time, the frequency (f) of the using mode is counted by the counter 17 and stored in an ROM14. The selection of the transmitter caliber is designated by the switch 16, and the corresponding compensation data beta and gamma are read out of the ROM12. Then the CPU11 calculates the correct flow rate value V0 from V0=Va/[beta+gamma(f-f0)]. This result can be converted into an analog signal through a D/A converter 13 and then delivered.

Description

【発明の詳細な説明】 本発明紘励振周波数の違いによるスパン変動を補償し喪
電磁流量針に関する。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electromagnetic flow needle that compensates for span fluctuations due to different excitation frequencies.

電磁流量針の発信器には流量と磁束に比例した信号が発
生するが、励磁電流の値が同じであっても励振周波数に
よって実際の磁束の値が異表るので、励振周波数に伴っ
て変換器出力のスパンが変動してしまう。このスパン変
動を補償した電磁流量計の一従来例を第１図に示す。図
において、１社励磁コイル、２社測定用管路、３ａと３
ｂａ電極、４は変換器、５は励振回路、６は励磁電流検
出用抵抗、７はＲｅ遅れ回路である。変換器４は電極か
らの流量比例信号に重畳する種々のノイズを除去すると
共和磁束に比例した比較電圧信号”ｒｄ　　で流量比例
信号を割算し、この割算結果を所定の出力形式で出力す
る。磁束の波形は第２図にφで示す如く、磁気回路の渦
流損等のため励磁電流波形１よりもやや遅れ且つなまっ
ている。そこで、励磁電流に比例した電圧を抵抗６で取
り出し、この電圧をＲＣ遅れ回路Ｔで波形調整して比較
電圧信号＋５ｒ社　としている。The electromagnetic flow needle transmitter generates a signal that is proportional to the flow rate and magnetic flux, but even if the excitation current value is the same, the actual magnetic flux value varies depending on the excitation frequency, so it is necessary to convert it according to the excitation frequency. The span of the instrument output fluctuates. FIG. 1 shows a conventional example of an electromagnetic flowmeter that compensates for this span variation. In the figure, one company's excitation coil, two companies' measurement pipes, 3a and 3
ba electrode, 4 is a converter, 5 is an excitation circuit, 6 is an excitation current detection resistor, and 7 is a Re delay circuit. After removing various noises superimposed on the flow rate proportional signal from the electrodes, the converter 4 divides the flow rate proportional signal by a comparison voltage signal "rd" proportional to the mutual magnetic flux, and outputs this division result in a predetermined output format. As shown by φ in Fig. 2, the waveform of the magnetic flux is slightly delayed and rounded compared to the excitation current waveform 1 due to eddy current loss in the magnetic circuit.Therefore, a voltage proportional to the excitation current is taken out by the resistor 6, and this The waveform of the voltage is adjusted by an RC delay circuit T to obtain a comparison voltage signal +5r.

ところが、第１図の従来例には次のような欠点がある。However, the conventional example shown in FIG. 1 has the following drawbacks.

■　ＲＣ遅れ回路７によシ波形合せしているため、高精
度表補償を必要とする場谷は、広範囲な励振周波数に対
しては不十分である。例えば、５０Ｈｚ励振と６０Ｈｚ
励振に発信器を共用できない。(2) Since the waveform is matched by the RC delay circuit 7, the frequency which requires high-precision table compensation is insufficient for a wide range of excitation frequencies. For example, 50Hz excitation and 60Hz
The oscillator cannot be shared for excitation.

■　磁束波形社測定用管路の口径など発信器のサイズに
よっても異なるため、ＲＣ遅れ回路７０時定数を発信器
のサイズ毎に調整せねばならない。■ Magnetic Flux Waveform Co., Ltd. The time constant of the RC delay circuit 70 must be adjusted for each size of the transmitter because it varies depending on the size of the transmitter, such as the diameter of the measuring pipe.

■　ＲＣ遅れ回路７を必要、とするが、これによシ発信
器が小形化できず、また回路自体に費用が掛ると共に比
較電圧の配線と工事が必要となってコスト高が免れない
。(2) The RC delay circuit 7 is required, but this makes it impossible to downsize the oscillator, and the circuit itself is expensive, as well as wiring and construction for the comparison voltage, which inevitably increases costs.

本発明は上記従来技術の欠点に鑑み、ＲＣ遅れ回路を必
要とせず、広範図表励振周波数に対してスパン変動を高
精度に補償できる電磁流量計の提供を目的とする。SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, it is an object of the present invention to provide an electromagnetic flowmeter that does not require an RC delay circuit and can compensate span fluctuations with high accuracy over a wide range of chart excitation frequencies.

この目的を達成するため、本発明では、励振周、波数や
発信器の種別によって異なるスパン変動を準算に本って
補正することとする。以下、図面を□参照して本発明の
詳細な説明する。In order to achieve this objective, in the present invention, span fluctuations that differ depending on the excitation frequency, wave number, and type of oscillator are corrected using quasi-calculation. Hereinafter, the present invention will be described in detail with reference to the drawings.

第３図に本発明の一実施例の回路構成を示す。FIG. 3 shows a circuit configuration of an embodiment of the present invention.

この例の電磁流量針は、信号処理にマイクロコンピュー
タを使用した定電流駆動式の低屑波励振形電磁流量針で
ある。予め、電磁流量針としての基本構成及び動作を簡
単に説明すると、商用周波数の誘導ノイズを除去するた
め励振回路５は商用電源８に同期して商用周波数の１　
、１　ｔ’　１等の周数２　４　８ 数の励磁電流を作る。励磁電流波形は正・負、正ｅゼロ
、負・ゼロ、正・ゼロ・負・ゼロの極性の吃のや、ある
いは正弦波、三角波２台形波などいずれでも良いが、こ
こでは第４図（ａ）の如き正・ゼロ・負・ゼロの繰返し
の矩形波励磁電流を側圧してｉ明する、この励磁電流に
対し電極３ａ　、　３ｂ間には第４図（ｂ）の流量比例
信号が発生するが、これには第４図（ｃ）の電磁誘導ノ
イズ、同図（ｄ）の商用周波ノイズ及び同図（・）の電
気化学的直流ノイズが重畳する。そこでプリアンプ９の
増幅出力ｔ−〜Φ変換器（アナログ・デジタル変換器）
１０でデジタル信号に変換し、第４図（ｆ）のタイミン
グａ、ｂ、ｃ、ｄ・・・でそれぞれのサンプル値Ｖａ、
Ｖｌ）、Ｖｃ、ＶｄをＣＰＵ　（マイクロコンピュータ
）１１に取込む。ＣＰＵｊｌはＲＯＭ（リード・オンリ
ー・メモリ）１２に記憶しているプロ５グラムによって
動作し、この例ではす、ンプル値を用いて次式（１）の
演算をすることによ、す、流量値Ｖ、を得ている。The electromagnetic flow needle in this example is a constant current driven, low waste wave excitation type electromagnetic flow needle that uses a microcomputer for signal processing. To briefly explain the basic configuration and operation of the electromagnetic flow needle in advance, the excitation circuit 5 synchronizes with the commercial power supply 8 to remove the commercial frequency induced noise.
, 1 t' 1, etc., and the number of cycles is 2 4 8 . The excitation current waveform may be positive/negative, positive/zero, negative/zero, positive/zero/negative/zero polarity, or a sine wave, triangular wave, two trapezoidal waves, etc., but here, the waveform shown in Figure 4 ( A rectangular wave excitation current with a repetition of positive, zero, negative and zero as shown in a) is applied to the side, and a flow rate proportional signal as shown in Fig. 4(b) is generated between the electrodes 3a and 3b in response to this excitation current. However, this is superimposed on the electromagnetic induction noise shown in FIG. 4(c), the commercial frequency noise shown in FIG. 4(d), and the electrochemical DC noise shown in FIG. 4(•). Therefore, the amplified output of preamplifier 9 t- to Φ converter (analog-to-digital converter)
10, it is converted into a digital signal, and the sample values Va,
Vl), Vc, and Vd are taken into the CPU (microcomputer) 11. The CPUjl operates according to a program stored in the ROM (read-only memory) 12, and in this example calculates the flow rate value by calculating the following equation (1) using the sample value. I am getting V.

但し、ＫＢｌｋＪ−例、示教である。However, KBlkJ-example is Jikyo.

Ｖ、＝Ｋ（−Ｖａ＋３Ｖｂ−３Ｖｃ＋Ｖｄ）　　＝式（
υつまり、各タイミングでのサンプル値には第４図（ｂ
）〜（ｅ）の波形にて斜線を付した部分が成分として含
まれるが、電磁誘導、ノイズは各サンプそタイミングが
励磁電流の変移時点から吟時１間ｔであることにより、
商用周波ノイズ、は−サンプルタイミングが商用周波数
に同期１７Ｃいること罠より、更に電気化学的ノイズ−
鵜サンプルタイミングが勢間隔であり励磁周部程度の短
時間ではサンプリング毎に一定変化量ΔＥで変化するも
のと見なせることＫよシ、それぞれ式（１）の演ＩＩＩ
Ｋよって各ノイズ成分が相殺されて除去される。このよ
うにして得られた流量値ｖ８はＤ／Ａ変換器（デジタル
争アナログ変換器）１３等により所定の出力形式の信号
よして出力される。なお、１４はＲＡＭ（ランダム・ア
クセ、ス、・メモリ）でサンプル値や定数の記憶に用４
いられる。また、１５はバス・ラインであ、る。V,=K(-Va+3Vb-3Vc+Vd)=Formula(
υIn other words, the sample value at each timing is as shown in Figure 4 (b
) to (e), the shaded parts are included as components, but electromagnetic induction and noise are caused by the fact that the timing of each sampling is 1 hour t from the time of change of the excitation current.
Commercial frequency noise is caused by electrochemical noise, which is caused by the fact that the sample timing is synchronized to the commercial frequency.
The cormorant sample timing is at regular intervals, and can be considered to change by a constant amount of change ΔE for each sampling in a short period of time such as the excitation period.
Each noise component is canceled out and removed by K. The flow rate value v8 thus obtained is output as a signal in a predetermined output format by a D/A converter (digital/analog converter) 13 or the like. Note that 14 is RAM (random access memory) used for storing sample values and constants.
I can stay. Further, 15 is a bus line.

次に、スパン変動の補償につりて説明する。補償方法は
２通シあシ、１つは、発信器口径などに基やく発信器種
類と励振周波数によるスパン補償量とを予め求めて第１
表のようなテーブルとしてＲＯＭ１２に記憶させておき
、第５図（ａ）の手順で、設定スイッチ１６による発信
器口径の・選択指定と、周波数カウンタ１Ｔによシ計測
された商用電源８０周波数とからＣＰＵ１１が補償量・
ｑをＲＯＭ１２よシ読み出し、前述した実測、の流量値
Ｖ−に対して次賽（２）の補償演算をする。Next, compensation for span fluctuations will be explained. There are two compensation methods: one is based on the transmitter caliber, the type of transmitter and the amount of span compensation based on the excitation frequency is determined in advance;
The table is stored in the ROM 12 as shown in the table below, and according to the procedure shown in FIG. The CPU 11 calculates the compensation amount from
q is read out from the ROM 12, and the following compensation calculation (2) is performed on the above-mentioned actually measured flow rate value V-.

１Ｉ ｖｏ＝　　□　　・・・式（２） 但し、Ｖｏは発信器磁気回路に渦流損がなく磁束が定常
値に達しているときの流量信号である。、ｖ８は実際に
得られる信号であり渦流損のためＶ、）よりやや小さく
発信器口径や励振周波数でその程度が異なる。なお、カ
ウンタ１Ｔの出力はＣＰＵ１１を商用周波数に同期させ
るためＣＰＵ１１の割込指令信号ともなる。また、符号
１８は入出力ボート（Ｉｌｏ）であシ、設定スイッチ１
６の読込指令信号を出す。1I vo= □ ...Equation (2) However, Vo is a flow rate signal when there is no eddy current loss in the transmitter magnetic circuit and the magnetic flux has reached a steady value. , v8 is the signal actually obtained, and is slightly smaller than V, ) due to eddy current loss, and its degree differs depending on the transmitter diameter and excitation frequency. Note that the output of the counter 1T also serves as an interrupt command signal for the CPU 11 in order to synchronize the CPU 11 with the commercial frequency. Also, reference numeral 18 is an input/output boat (Ilo), and setting switch 1
Issues a reading command signal of 6.

第１表 一方、他の補償方法は変換器と組合せる発信器が限られ
ていて励振周波数対スパン変動量の関係式が発信器口径
側に判っている場合に都合の良い方法であり、この関係
式の演算補正プログラムをＲＯＭ１２　Ｋ記憶させてお
き、使用状態で読込まれる周波数信号に応じた演算補正
を第ｓｒＩ！Ｊ（ｂ）の手順で行うのである。Table 1 On the other hand, other compensation methods are convenient when the number of oscillators that can be combined with the converter is limited and the relational expression between excitation frequency and span variation is known for the oscillator aperture. A computation correction program for the relational expression is stored in the ROM 12K, and the computation correction according to the frequency signal read in the usage state is performed in the srI! This is done using the procedure J(b).

つまり、商用周波数の５０Ｈｚ　　と６ＧＨｚ相互間程
１ｉｔ）周波数変化に対しては実測値Ｖ、の変動は直線
近似でも十分な補償精度が得られるので、次式（３）の
演算で正しい流量値Ｖ（、を算出できる。In other words, for the frequency change between the commercial frequency of 50 Hz and 6 GHz (1 it), sufficient compensation accuracy can be obtained for the fluctuation of the actual measured value V by linear approximation, so the correct flow rate value V can be obtained by calculating the following equation (3). (, can be calculated.

ここで、ｆｔ１ｉ使用状態の周波数、ｆｏは基準周波数
、βとｒは発信器口径ではぼ決定される値であり、βと
γはＲＯＭ１２　Ｋ第２表のようなテーブルとして予め
記憶させておく。Here, ft1i is the frequency in use, fo is the reference frequency, β and r are values roughly determined by the oscillator aperture, and β and γ are stored in advance in the ROM 12 K as a table such as Table 2.

第２表 使用状＠（Ｄ周波数ｆはカウンタ１７により計測されて
ＲＡＭ１４に記憶される。一方、設定スイッチ１６ｒ−
より発信器口径が選択指定されると、口径に対応するβ
とｒがＲＯＭＩ２から読出される。Table 2 Usage statement @(D Frequency f is measured by counter 17 and stored in RAM 14. On the other hand, setting switch 16r-
When the transmitter aperture is selected and specified, β corresponding to the aperture is
and r are read from ROMI2.

ＣＰＵ１１は、ＲＯＭ１２に記憶された補正式（３）の
アルゴリズムによｌ）　ｆ　、　ｆｏ　、β、ｒ及びＶ
、を用いて補正式（３）の演算をし、この結果がＤ／Ａ
変換器１３によシアナログ信号として出力される。The CPU 11 uses the algorithm of correction formula (3) stored in the ROM 12 to calculate f, fo, β, r, and V.
, is used to calculate the correction formula (3), and the result is D/A
The converter 13 outputs it as an analog signal.

なお、上記各実施例では商用電源８０局波数を計測して
演算に用いているが、励磁電流の周波数を直接計測する
構成としても良い。また各偶は定電流励振の場合である
が、励振回路が電圧励振の場合は励磁電流変動による出
力誤差を除去するため、励磁電流で流量信号を除算する
演算を行うと良い。更に、励振方式及びｖ８を求める信
号処理方式は例示した方式に限定されず、各種の方式に
対して本発明を適用てきることれ言うまでもない。In each of the above embodiments, the wave numbers of 80 stations of the commercial power supply are measured and used for calculation, but a configuration may also be adopted in which the frequency of the excitation current is directly measured. Further, each case is for constant current excitation, but if the excitation circuit is voltage excitation, it is preferable to perform an operation of dividing the flow rate signal by the excitation current in order to eliminate output errors due to excitation current fluctuations. Further, the excitation method and the signal processing method for determining v8 are not limited to the exemplified method, and it goes without saying that the present invention can be applied to various methods.

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

第１．２図社従来技術に係〕、第１図れ構成図、第２図
社波形図、第３〜５図は本発明に係シ、第３図は構成図
、第４図は波形−、第５図は演算手順の図である。 図面中、１＃ｉ励磁コイル、２は側足用管路、３ａと３
ｂｔｉ電極、５Ｌ励振回路、８＃Ｓｊ：商用電源、１１
はＣＰＵ（Ｗイタ０コンピユータ）、１１ｔＲｏＭ（リ
ード−オンリー−メモリ）、１４はＲＡＭ（ランダム・
アクセス・メモリ）、１５ｔｊ：パス・ライン、１６紘
発信器ロ径の設定スイッチ、１Ｔは周波数カウンタであ
る。Figure 1.2 is related to the prior art], Figure 1 is a block diagram, Figure 2 is a waveform diagram, Figures 3 to 5 are related to the present invention, Figure 3 is a configuration diagram, and Figure 4 is a waveform diagram. , FIG. 5 is a diagram of the calculation procedure. In the drawing, 1#i excitation coil, 2 are side leg conduits, 3a and 3
bti electrode, 5L excitation circuit, 8#Sj: Commercial power supply, 11
is CPU (Wita 0 computer), 11tRoM (read-only-memory), 14 is RAM (random
access memory), 15tj: pass line, 16 oscillator diameter setting switch, 1T is a frequency counter.

Claims (1)

【特許請求の範囲】[Claims] （１）　　電磁流量、計において、励振周波数を計測す
る手段と、電磁流置針発信器の種別を設定する手段と、
発信器種別毎に各励振周波数が流量値に及ぼすスパン変
動の補償データを予め記憶しているメモリと、計測した
周波数及び設定された発信器種別に対応する補償データ
を上記メモリから読出してこの補償データで流量値のス
パン変動を補償するプログラム動作の演算手段とを備え
たことを特徴とする電磁流量針。 （２１電磁流量針において、励振周波数を計測する手段
と、電磁流置針発信器の種別を設定する手段と、流量値
に対する励振周波数対スパン変動量の補正式のアルゴリ
ズムを記憶しているメモリと、発信器種別により決まり
種別設定によってメモリから読出される定数及び計測し
た周波数を用いて上記アルゴリズムにより流量値のスパ
ン変動を補正するプログラム動作の演算手段とを備えた
ことを特徴とする電磁流量針。(1) In an electromagnetic flow rate meter, a means for measuring the excitation frequency, a means for setting the type of the electromagnetic flow pointer transmitter,
This compensation is performed by reading out from the memory the compensation data for the span fluctuations that each excitation frequency affects on the flow rate value for each oscillator type, and the compensation data corresponding to the measured frequency and the set oscillator type. An electromagnetic flow needle characterized by comprising a program operation calculation means for compensating for span fluctuations in flow rate values using data. (In the electromagnetic flow needle No. 21, a means for measuring the excitation frequency, a means for setting the type of the electromagnetic flow needle transmitter, and a memory storing an algorithm for a correction formula of the excitation frequency versus span fluctuation amount for the flow rate value, An electromagnetic flow needle characterized in that it is equipped with a calculation means for program operation that corrects span fluctuations in the flow rate value according to the above algorithm using a constant determined by the type of transmitter and read from the memory according to the type setting and the measured frequency.