JPS58115324A - Electromagnetic flowmeter - Google Patents
Electromagnetic flowmeterInfo
- Publication number
- JPS58115324A JPS58115324A JP21252481A JP21252481A JPS58115324A JP S58115324 A JPS58115324 A JP S58115324A JP 21252481 A JP21252481 A JP 21252481A JP 21252481 A JP21252481 A JP 21252481A JP S58115324 A JPS58115324 A JP S58115324A
- Authority
- JP
- Japan
- Prior art keywords
- zero
- negative
- positive
- excitation
- voltage
- 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.)
- Granted
Links
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
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Fluid Mechanics (AREA)
- General Physics & Mathematics (AREA)
- Measuring Volume Flow (AREA)
Abstract
Description
【発明の詳細な説明】
本発明は、低周波励磁方式の電磁流量針の改良に関する
。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a low frequency excitation type electromagnetic flow needle.
一般に電磁流量針は、流体の流れ′方向に対して喬直に
磁界を与え、同時に流体流路中の電気的信号の変化を検
出し、これに基づいて流体の流量を計測するように構成
されている。最近の電磁流量針は、交流励磁方式や直流
励磁方式に比して零点の安定性にすぐれている台形波励
磁や方形波励磁などと呼ばれている低周波励磁方式のも
のが多く用いられている。この種の低周波励磁方式の電
磁流量計において、特に電磁流量計発信器の励磁コイル
に定常値が負・零・正・零の順で繰り返す励磁電流を供
給し、電磁流量計発信器から与えられる励磁電流の定常
値が負・零・正・零の各期間の信号電圧eal”a2”
a3”a4を用いて、信号処理回路で実質的K Cea
1+ ea□) −(ea3+ea4’ 7する演算を
行うものは、電気化学的な直流電圧や回路に基づくオフ
セット電圧成分および励磁電流の切換えに伴うノイズ成
分の影響を除去し、流量成分に関連し死出力を得ている
。゛ところでこの方式の電磁流量針においても、電気化
学的な直流電圧が変動しオフセット電圧成分が変化する
とその影響をもろに受け、出力変動はまぬがれ得なかっ
た。しかもオフセット電圧は、数百mVにも達し、流量
成分のスパン(1〜10mV)に対し非常に大きく、か
つその過渡変化は直線と見做すことができない。そこで
、信号電圧ea2とea3にそれぞれ係数を乗じた後(
ea4−3ea2 ” 3ea2− eal)なる演算
を行えば、オフセット電圧成分を2次式近似で除去でき
る。しかし実験によればオフセット電圧成分は正および
負方向に振れるが、その振れは一1v〜+1vていどを
越えることが々く、その電位変化、は変曲点を必ずもっ
て・いることが確認された。このためオフセット電圧成
分を2次式近似で除去する場合には、電位変化の変曲点
で大きな誤差が生ずる。また電磁流量計における励磁電
流の最小値は、信号処理回路の入力換算ノイズとの比に
よって決定され、入力換算ノイズはほぼベクトル加算さ
れるため、(ea工+ea2 ’−ea3− ea4)
なる演算を行う本のと(ea4−3ea3 ”3ea2
−ea□)なる演算を行うものとの比は五すyJ〒1”
: D−[す藷−284,4□となり、後者の演算を
行うものの方が同一の大きさの流量信号を得る丸めの励
磁電流の大きさが2.24倍となシ、消費電力は5倍も
大きくなる。In general, an electromagnetic flow needle is configured to apply a magnetic field perpendicularly to the fluid flow direction, simultaneously detect changes in electrical signals in the fluid flow path, and measure the fluid flow rate based on this. ing. Most recent electromagnetic flow needles use low-frequency excitation methods, such as trapezoidal wave excitation and square wave excitation, which have superior zero point stability compared to AC excitation and DC excitation methods. There is. In this type of low-frequency excitation type electromagnetic flowmeter, in particular, an excitation current is supplied to the excitation coil of the electromagnetic flowmeter transmitter with a steady value that repeats in the order of negative, zero, positive, and zero. The signal voltage eal"a2" during each period when the steady value of the excitation current is negative, zero, positive, and zero.
Using a3"a4, the signal processing circuit can effectively convert K Cea
1+ea□) -(ea3+ea4'7) The device that calculates By the way, even with this type of electromagnetic flow needle, when the electrochemical DC voltage fluctuates and the offset voltage component changes, it is affected by this, and output fluctuations cannot be avoided. reaches several hundred mV, which is extremely large compared to the span of the flow rate component (1 to 10 mV), and its transient change cannot be regarded as a straight line.Therefore, the signal voltages ea2 and ea3 are multiplied by coefficients, respectively. After (
By performing the calculation ea4-3ea2 '' 3ea2- eal), the offset voltage component can be removed by quadratic approximation. However, according to experiments, the offset voltage component swings in the positive and negative directions, but the swing is between -1v and +1v. It was confirmed that the potential change always has an inflection point.Therefore, when removing the offset voltage component by quadratic approximation, it is necessary to remove the inflection point of the potential change. In addition, the minimum value of the excitation current in an electromagnetic flowmeter is determined by the ratio to the input conversion noise of the signal processing circuit, and since the input conversion noise is almost vector added, (ea + ea2' - ea3-ea4)
There is a book that performs the calculation (ea4-3ea3 ”3ea2
-ea□) is the ratio of 5yJ〒1”
: D-[Size=-284,4□, and the one that performs the latter calculation has 2.24 times the magnitude of the rounded excitation current that obtains the same magnitude of flow signal, and the power consumption is 5 It will be twice as big.
本発明は、電磁流量計発信器から与えられる励磁電流の
定常値が負・零・正・零・負・零・正・零の各期間の信
号電圧をそれぞれeal”a2”a3’ea4’ ea
5”a6”a7’ ea8としたとき、信号処理回路で
実質的K(ea6−3ea5+2ea4+2ea3−3
ea2+ea1)または(ea8−3efL7+2ea
6+2ea5−3ea4+ea3)なる演算を行い、少
ない消費電力でオフセット電圧成分を3次式近似で除去
できる低周波励磁方式の電磁流量針を実現したものであ
る。In the present invention, the steady value of the excitation current given from the electromagnetic flowmeter transmitter is negative, zero, positive, zero, negative, zero, positive, zero, and the signal voltages in each period are eal"a2"a3'ea4'ea
5"a6"a7' ea8, the signal processing circuit effectively calculates K(ea6-3ea5+2ea4+2ea3-3
ea2+ea1) or (ea8-3efL7+2ea
6+2ea5-3ea4+ea3) to realize a low frequency excitation type electromagnetic flow needle that can remove offset voltage components by cubic approximation with low power consumption.
第1図は本発明電磁流量計の〒実施例を示す接続図であ
る。図において、1は励磁回路で 直流定電流源11と
、定電流源11からの電流を切換えるスイッチ12.1
3とを有している。2は電磁流量計発信器で、励磁゛コ
イル21電流体が流れるパイプ22および電極23.2
4を備えている、)3は信号処理回路で、電磁流量計発
信器2の電極23.24間に誘起する電圧eを増幅する
交流増幅器31と 交流増幅器31の出力電圧ebが加
えられる直列接続された6側のサンプルホールド回路3
2 〜32.と、これらサンプルホールド回路32 〜
32 の出力ec工〜a f
ec6が各々係数器331〜33.を介して加えられる
演算回路34と、演算回路34の出力edを反転するイ
ンバータ35と、演算回路34の出力edとインバータ
35の出力exとを切換えるスイ、゛チ36と、スイッ
チ36で選択されたeまたはe、をサンプルホールドす
るサンプルホールド回路37および、励磁回路1の゛ス
イッチ12.13を制御するパルスPla”lbと、サ
ンプルホールド回路32 〜32fのサンプリングを制
御するパルスP2a = p2fと、切換スイッチ36
を制御するパルスp3および、サンプルホールド回路3
r?のす/ブリングを制御するパルスp4を第2図に示
す如きタイミングで発生するタイミングパルス発生回路
ユ8とを有している。そして係数器33 〜33fの係
数に1〜に6はそれぞれに1− K6謂1. K2−に
5−3゜K3−に4−2に選ばれており、演算器34で
、(ecl−3e02” 2e03+ 2e04−3e
c5+ ”c6 )なる加減演算を行うようになってい
る。FIG. 1 is a connection diagram showing an embodiment of the electromagnetic flowmeter of the present invention. In the figure, 1 is an excitation circuit that includes a DC constant current source 11 and a switch 12.1 that switches the current from the constant current source 11.
3. 2 is an electromagnetic flowmeter transmitter, which includes an exciting coil 21, a pipe 22 through which a current flows, and an electrode 23.2.
) 3 is a signal processing circuit, which is connected in series with an AC amplifier 31 that amplifies the voltage e induced between the electrodes 23 and 24 of the electromagnetic flowmeter transmitter 2, and to which the output voltage eb of the AC amplifier 31 is applied. sample hold circuit 3 on the 6 side
2 to 32. and these sample and hold circuits 32 ~
The outputs ec~af ec6 of 32 are sent to the coefficient multipliers 331~33.33, respectively. an arithmetic circuit 34 added through the arithmetic circuit 34, an inverter 35 that inverts the output ed of the arithmetic circuit 34, a switch 36 that switches between the output ed of the arithmetic circuit 34 and the output ex of the inverter 35, and a switch 36 selected by the switch 36. A sample hold circuit 37 that samples and holds e or e, a pulse Pla'lb that controls the switches 12 and 13 of the excitation circuit 1, and a pulse P2a = p2f that controls sampling of the sample hold circuits 32 to 32f, Changeover switch 36
pulse p3 that controls the sample and hold circuit 3
r? It has a timing pulse generating circuit 8 which generates a pulse p4 for controlling the stop/bring at the timing shown in FIG. The coefficients 1 to 6 of the coefficient units 33 to 33f are respectively 1-K6, so-called 1. 5-3 degrees are selected for K2- and 4-2 are selected for K3-, and the arithmetic unit 34 calculates (ecl-3e02" 2e03+ 2e04-3e
c5+"c6)" addition/subtraction operation is performed.
このように構成した本発明の動作”を第2図の波形図を
参照して以下に説明する。まずスイッチ12゜13は第
2図に示す如き駆動パルスp1.. p工、で制御され
、plaがオンとなっている期間T工に定電流源11か
らの電流工、を正方向に励磁コイル21に流し、plb
がオンとなっている期間T3に定電流源11からの電流
Iwを逆方向に切換えて励磁コイル21に流(7、Pl
a”lbが共(オフと表りている期間T2.T4には励
磁コイル21に電流を流さない。よって励磁コイル21
Cは第2図に示すように定常値が正の励磁期間T工と負
の励磁期間T3および零の休止期間T2IT4があり、
定常値が正・零・負・零の順で繰り返す励磁電流Iwが
供給される。なお、励磁電流IWはスイッチ12.13
で切換えられたとき、定電流源11は有限の出力電圧し
か供給できぬから励磁コイル21のインダクタンスと抵
抗による時定数で実際には立上り、立下りの部分で遅れ
を伴ったのち定常値となるが図では省略しである。電磁
流量計発信器2の電極23.24間には励磁電流工wK
応じた誘起電圧eが発生−する、誘起電圧eKは第2図
に示すよa
aうに、パイプ22を流れる流体の流量FK
比例した流量成分v8の外に、電気化学的な直流電位や
回路によるオフセット電圧成分vnと、励磁電流の切換
えに伴うノイズ成分V。とが重畳されている。その結果
第2図に示す励磁電流の定常値が負・零・正・零・負・
零・正・零・負の各期間に発生する誘起電圧eを画定関
隔Δtでサンプリングした信号電圧eat”a2”a3
’ ”a4’ ”a5”a6”a7’ %8”a9はそ
れぞれ次式で与えられる。なおオフセット電圧成分Vは
テーラ展1して3次式近似で示しである。The operation of the present invention constructed in this way will be explained below with reference to the waveform diagram in FIG. 2. First, the switches 12 and 13 are controlled by drive pulses p1... During the period T when pla is on, the current from the constant current source 11 is sent to the excitation coil 21 in the positive direction, and plb
During the period T3 when Pl is on, the current Iw from the constant current source 11 is switched in the opposite direction to flow through the exciting coil 21 (7, Pl
During the period T2 and T4 in which both a''lb are shown as OFF, no current is passed through the excitation coil 21. Therefore, the excitation coil 21
As shown in FIG. 2, C has an excitation period T with a positive steady-state value, a negative excitation period T3, and a rest period T2IT4 with a zero value.
An excitation current Iw whose steady-state value repeats in the order of positive, zero, negative, and zero is supplied. Note that the excitation current IW is controlled by switches 12 and 13.
When switched, the constant current source 11 can only supply a finite output voltage, so it actually rises and falls with a delay due to the time constant due to the inductance and resistance of the exciting coil 21, and then reaches a steady value. is omitted in the figure. There is an excitation current wire wK between the electrodes 23 and 24 of the electromagnetic flowmeter transmitter 2.
A corresponding induced voltage e is generated, and the induced voltage eK is a as shown in Fig. 2.
a, the flow rate FK of the fluid flowing through the pipe 22
In addition to the proportional flow rate component v8, there is an offset voltage component vn due to an electrochemical DC potential or circuit, and a noise component V accompanying switching of the excitation current. are superimposed. As a result, the steady-state values of the excitation current shown in Figure 2 are negative, zero, positive, zero, negative,
Signal voltage eat"a2"a3 obtained by sampling the induced voltage e generated in each period of zero, positive, zero, and negative at a defined interval Δt
``a4''``a5''a6''a7'%8''a9 are given by the following equations.The offset voltage component V is expressed by Taylor expansion 1 and approximated by a cubic equation.
信号処理回路3では、まず電磁流置針発信器2かもの誘
起電圧eaを増幅器31で増幅し、第2図に示す如きタ
イミングで発生するサンプリングツ(ルスP21LKよ
って、信号電圧e、L1〜’a9 K 相”4 t ;
b増幅器31の出力が順次サンプルホールド回路321
にホールドされる。サンプルホールド回@ 32.のホ
ールド値”clは第2図に示す如きタイミングで発生す
るサンプリングパルスP2b Kよってサンプルホール
ド回路32bにホールドされる。同様にサンプルホール
ド回路32b〜32eのホールド値ec2〜e05は第
2図に示す如きタイミングで発生する’t y )IJ
y /パルスP2゜〜P2fKよってそれぞれサンプ
ルホールド回路32 〜32.にホールドされる。し九
がりて、サンプルホールド回路32aに信号圧”a6に
関連した電圧がホールドされ死時点では、サンプルホー
ルド回路32b〜32fにはea5〜elL1にそれぞ
れ関連した電圧がホールドされ、サンプルホールド回路
32. K ’a7に関連した電圧がホールドさ五た時
点では、サンプルホールド回路32b〜32 KはeI
L6〜01□にそれぞれ関連した電圧がホールドされる
。これらサンプルホールド回路321〜32.のホール
ド電圧”cl〜e、sはそれぞれ係数器331〜33.
を介して演算回路34で”cl−3e02+ 2ec3
+ 2e、 −3e、5+・136)なる演算が行われ
る。In the signal processing circuit 3, first, the induced voltage ea of the electromagnetic flow pointer oscillator 2 is amplified by the amplifier 31, and the signal voltage e, L1 to 'a9 K phase”4t;
The output of the b amplifier 31 is sequentially transferred to the sample hold circuit 321.
is held. Sample hold time @ 32. The hold value "cl" is held in the sample hold circuit 32b by the sampling pulse P2bK generated at the timing shown in FIG. 2. Similarly, the hold values ec2 to e05 of the sample hold circuits 32b to 32e are shown in FIG. 't y ) IJ that occurs at a timing like
y/pulses P2° to P2fK, sample and hold circuits 32 to 32. is held. Then, the sample and hold circuit 32a holds the voltage related to the signal voltage "a6," and at the time of death, the sample and hold circuits 32b to 32f hold the voltages related to ea5 to elL1, respectively, and the sample and hold circuits 32. At the point when the voltage associated with K'a7 is held, the sample and hold circuits 32b to 32K are eI
Voltages associated with L6 to 01□ are held. These sample and hold circuits 321-32. The hold voltages ``cl~e, s'' are the coefficient multipliers 331~33., respectively.
"cl-3e02+ 2ec3" in the arithmetic circuit 34 via
+2e, -3e, 5+·136) are performed.
その結果演算回路34の出力端にはサンプルホールド回
路32sLK信号電圧@、6 K相当する増幅器31の
出力がホールドされたと自の演算結果ed1と、信号電
圧01□に相当する増幅器31の出力がホールドされた
ときの演算結果”d2と、信号電圧e、8に相当する増
幅器31の出力がホールドされたときの演算結果e と
、信号電圧−8に相当する増幅器313
の出力がホールドされたときの演算結果ed4を順次繰
に返す波形の電圧eが得られる゛。そしてe6、〜ed
4は増幅器31のゲインをkとするとそれぞれ次式で与
えられる。As a result, at the output terminal of the arithmetic circuit 34, the output of the amplifier 31 corresponding to the sample and hold circuit 32sLK signal voltage @6K is held, the own arithmetic result ed1, and the output of the amplifier 31 corresponding to the signal voltage 01□ are held. The calculation result "d2" when the signal voltage e,8 is held, the calculation result e when the output of the amplifier 31 corresponding to the signal voltage e,8 is held, and the calculation result "d2" when the output of the amplifier 313 corresponding to the signal voltage -8 is held. A waveform voltage e is obtained by sequentially repeating the calculation result ed4. Then, e6, ~ed
4 are given by the following equations, where k is the gain of the amplifier 31.
edlxk(ea6−3elL5+2ea、+2e、3
−3e、2+elL1)w4kV、 (2)e
d211Ik(e、7−36.6+2e、5+2@、、
−3ea3+8,2)−4k(V、+2V、) (3
)ed3−k(eIL8−3e、7+2e、6+2e、
5−3ea、+esL3)−−4kV、
(4)ed4−IJ−、−3e、8+2e、7+2
e、6−3aIL5+e’、4)−4k(V、+2V、
) (5)よって演算回路34の出力には、サ
ンプルホールド囲路5zKIIlk電流の定常値が正ま
たは負のときの信号電圧に相当゛する増幅器31の出力
がホールドされ死時点では励磁電流の切換えに伴うノイ
ズ成分Vが重畳されているが、定常値が零のと色の信号
電圧に相当する増幅器31の出力がホールドされ死時点
では5次式近似のオフセット電圧成分vnO〜vn3が
除去されるとともに励磁電流の切換えに伴うノイズ成分
veも除去され流量成分vsのみを得ることができる。edlxk(ea6-3elL5+2ea,+2e,3
-3e, 2+elL1)w4kV, (2)e
d211Ik(e, 7-36.6+2e, 5+2@,,
-3ea3+8,2)-4k(V,+2V,) (3
) ed3-k (eIL8-3e, 7+2e, 6+2e,
5-3ea, +esL3)--4kV,
(4) ed4-IJ-, -3e, 8+2e, 7+2
e, 6-3aIL5+e', 4)-4k(V, +2V,
) (5) Therefore, the output of the amplifier 31 corresponding to the signal voltage when the steady-state value of the sample-and-hold circuit 5zKIIlk current is positive or negative is held at the output of the arithmetic circuit 34, and the excitation current is not switched at the time of death. Although the accompanying noise component V is superimposed, the output of the amplifier 31 corresponding to the color signal voltage whose steady value is zero is held, and at the time of death, the offset voltage components vnO to vn3 approximated by the quintic equation are removed. The noise component ve accompanying the switching of the excitation current is also removed, and only the flow rate component VS can be obtained.
そこで第2図に示すタイミングで発生するパルスp3で
切換スイッチ36を駆動し、演算回路34の出力がea
□のときはインバータ35を介して取シ出し第2図に示
すタイミングで発生するサンプリングパルスpで演算回
路34の出力e6、とインバータ35を介して取り出す
ed3をす/プルホールド回路37に交互に与える。そ
の結果サンプルホールド回路37の出力端には流量成分
VKfi連した出力電圧eが得られる。Therefore, the selector switch 36 is driven by the pulse p3 generated at the timing shown in FIG. 2, and the output of the arithmetic circuit 34 is
When □, the output e6 of the arithmetic circuit 34 and the output ed3 of the arithmetic circuit 34 are taken out via the inverter 35 and the output e6 of the arithmetic circuit 34 is taken out via the inverter 35, and the output ed3 is sent to the pull-hold circuit 37 alternately with the sampling pulse p generated at the timing shown in FIG. give. As a result, an output voltage e connected to the flow rate component VKfi is obtained at the output end of the sample hold circuit 37.
このように本発明においては、励磁電流の切換えに伴う
ノイズ成分Vおよびオフセ、ト電圧成分を5次式近似で
除去できる丸め、オフセット電圧成分が変曲点をもつよ
うな場合にも有効に除去できる。しかも信号処理回路5
の入力換算ノイズは12+32+ 22+ 22+ 3
+ 1 露5.68と表る逅、流量成分Vが4倍さ
れているため、オフセット電圧成分を2次式近似で除去
する場合に比して、同一の大暑さの流量信号を得るのに
必要な励磁電流は59χでよく、消費電力d 35%
Kも減少させることができる。更に、この方武嬬流量変
動に対して、積算誤差を生じない特質も有しておシ、ラ
ンプ状の流量変化に対するオフセットも生じない。In this way, in the present invention, the noise component V and the offset voltage component accompanying switching of the excitation current can be removed by fifth-order approximation, and the offset voltage component can be effectively removed even when the offset voltage component has an inflection point. can. Moreover, the signal processing circuit 5
The input equivalent noise is 12+32+ 22+ 22+ 3
Since the flow rate component V is multiplied by 4, which is expressed as + 1 dew 5.68, it takes more time to obtain the same flow rate signal of large heat than when the offset voltage component is removed by quadratic approximation. The required excitation current may be 59χ, and the power consumption d is 35%.
K can also be reduced. Furthermore, this method has the characteristic that no integration error occurs due to fluctuations in flow rate, and no offset occurs due to ramp-like flow rate changes.
なお上述では、励磁電流の定常値が負・零・正零・負・
零の各期間の信号電圧を用いる(2)式の演算結果と正
・零・負・零・正・零の各期間の信号電圧を用いる(4
)式の演算結果を交互に出力する場合を例示し九が、い
ずれか一方を出力するようにしてもよい。ただし実施例
のように交互に出力する場合の方が応答性を2倍よくで
牟る利点がある。In addition, in the above, the steady value of the excitation current is negative, zero, positive zero, negative,
Using the calculation result of equation (2) using the signal voltage for each period of zero and the signal voltage for each period of positive, zero, negative, zero, positive, and zero (4
9 is an example of a case in which the calculation results of the formula ( ) are output alternately, but either one may be output. However, the case where the signals are output alternately as in the embodiment has the advantage that the response is twice as good.
また上述では、増幅器31の出力ebをサンプルホール
ド回路32 K直接部え為場合を例示したが、第3図
に示すように増幅器出力ebを積分器39で一定時間積
分し死後サンプルホールド回路32aに与えるよう和し
てもよい。この場合積分時間T8を商用電源周期の整数
倍に選べば電源周波数ノイズの影響を除去できる。なお
第5図においては、積分器39として抵抗RIと、演算
増幅器Opと、 opの帰還回路に接続された積分用コ
ンデンサCIと、入力積分時間T8を制御するタイミン
グスイッチTSおよび積分値をリセットするリセットス
イッチR3を有し、T8およびR8はタイミングパルス
発生器38からのパルスP5.P6によって駆動される
ものが例示されている。また信号処理回路5は第4図に
示すようにディジタル演算を行うマイクロプロセ、す4
0を用・
いて構成してもよい。第4図においては、積分器39の
出力e工がA/D変換器41でディジタル信号に変換さ
れてマイクロプロセ、す40に与えられ、マイクpプロ
セ、す40で卜(2)式または(4)式に相当するディ
ジタル演算を行い流量成分VIC相当するディジタル値
を出力し、D/A変換器42でアナログ信号に変換した
後サンプルホールド回路37にホールドして、その出力
端に流量成分VK関連した出力電圧eoを得るものが例
示されている。なお第4図において積分器39で基準電
圧・1をパルスp7で駆動されるスイッチTSIを介し
て与え、eを一定時間だけ積分した値をA/D変換器4
1でディジタル信号に変換後マイクロプロセ、す40に
与えて、スパン調整等を行うようKしてもよい。さらに
上述では励磁電流工、として矩形波の、場合を例示した
が、台形液や商用交流電源を周波数変換し死後整流して
得た波形のもの等必要に応じて種々の波形のものを用い
ることができる。Furthermore, in the above description, the case where the output eb of the amplifier 31 is directly transferred to the sample and hold circuit 32K is illustrated, but as shown in FIG. You can also sum it up to give. In this case, if the integration time T8 is selected to be an integral multiple of the commercial power supply cycle, the influence of power supply frequency noise can be removed. In FIG. 5, the integrator 39 includes a resistor RI, an operational amplifier Op, an integrating capacitor CI connected to the feedback circuit of op, a timing switch TS that controls the input integration time T8, and resets the integral value. has a reset switch R3, T8 and R8 are pulses P5. The one driven by P6 is illustrated. Further, the signal processing circuit 5 includes a microprocessor that performs digital calculations, as shown in FIG.
It may also be configured using 0. In FIG. 4, the output e of the integrator 39 is converted into a digital signal by the A/D converter 41 and given to the microprocessor 40. 4) A digital calculation corresponding to the formula is performed and a digital value corresponding to the flow rate component VIC is output, which is converted into an analog signal by the D/A converter 42 and held in the sample hold circuit 37, and the flow rate component VK is output to the output terminal. An example is shown that yields an associated output voltage eo. In FIG. 4, the integrator 39 applies the reference voltage 1 via the switch TSI driven by the pulse p7, and the A/D converter 4 integrates e over a certain period of time.
After converting the signal into a digital signal in step 1, the signal may be sent to a microprocessor 40 to perform span adjustment or the like. Furthermore, although the above example uses a rectangular wave as the excitation current, various waveforms may be used as necessary, such as a waveform obtained by converting the frequency of a trapezoidal liquid or a commercial AC power source and rectifying it after death. I can do it.
このように本実INにおいては、励磁電流の定常値が負
・零・正・零・負・零・正・零の順で変化するときの各
期間の信号電圧をeee ・al’ a2ラ a3
’ a4’
”a5’ ”a6’ %7’ ”a8とし九とL信号処
理回路で実質的K (”−−−3e、s + 2e、4
+ 2e、3−3e、L2 +”al ) t 九は(
e、8−3e、7+ 2e、、 + 2e、5−3*、
4+ @IL3) lkる演算を行りているので、少な
い消費電力で励磁電流の切換に伴うノイズ成分およびオ
フセット電圧成分を5次式近似で除去で―る低周波励磁
方式の電磁流量針が得られる。In this way, in the actual IN, the signal voltage in each period when the steady value of the excitation current changes in the order of negative, zero, positive, zero, negative, zero, positive, zero is eee ・al' a2 la a3
'a4'``a5'``a6'%7' ``A8, 9 and L signal processing circuit effectively K (''---3e, s + 2e, 4
+ 2e, 3-3e, L2 +”al ) t Nine is (
e, 8-3e, 7+ 2e,, + 2e, 5-3*,
4+ @IL3) Since the computation is performed, it is possible to obtain a low-frequency excitation type electromagnetic flow needle that can remove noise components and offset voltage components associated with excitation current switching using quintic approximation with low power consumption. It will be done.
第1図は本発明電磁流量針の一実施例を示す接続図、第
2図はその動作説明の丸め波形図、第5図および111
4図は本発明電磁流量針の他の実施例を示す接続図であ
る。
1・・・励磁回路、2・・・電磁流置針発信器、21・
・・励磁コイル、23.24・・・電極、3・・・信号
処理回路、31・・・交流増幅器、32〜32 ・・
・サンプルホールド回a f
路、34・・・演算器、37・・サンプルホールド回路
、39・・・積分器、40・・・マイク資プロ七、す、
41・・・A/D 変変器、42・・・D/A変換器、
38・・・タイミングバk x 発生器。Figure 1 is a connection diagram showing one embodiment of the electromagnetic flow needle of the present invention, Figure 2 is a rounded waveform diagram explaining its operation, Figures 5 and 111.
FIG. 4 is a connection diagram showing another embodiment of the electromagnetic flow needle of the present invention. 1... Excitation circuit, 2... Electromagnetic flow pointer transmitter, 21.
... Excitation coil, 23.24 ... Electrode, 3 ... Signal processing circuit, 31 ... AC amplifier, 32-32 ...
・Sample hold circuit a f circuit, 34... Arithmetic unit, 37... Sample hold circuit, 39... Integrator, 40... Microphone equipment processor 7,
41...A/D converter, 42...D/A converter,
38...timing bar k x generator.
Claims (1)
正の願で繰り返す励磁電流を供給する励磁回路と、電磁
流量計発信器から与えられる励磁電流の定常値が負・零
・正・零・負・零・正・零の各期間の信号電圧を’al
”a2’ ”a3”a4’ ea5’ea6’ ea7
”a8としたとき実質的K(ea6−3ea5+2e1
4+2ea3−3ea2 ” ”at”たは”a8−3
eEL7” 2elLe + 2e、5−3elL4+
ea3)なる演算を行い、オフセット電圧成分を3次式
近似で除去して流量信号を得る信号処理回路とを有する
電磁流量針。If the excitation coil of the electromagnetic flowmeter transmitter has a steady value of zero, negative,
An excitation circuit that repeatedly supplies an excitation current with a positive request and a steady value of an excitation current given from an electromagnetic flowmeter transmitter are used to detect signal voltages during each period of negative, zero, positive, zero, negative, zero, positive, and zero. 'al
"a2""a3"a4'ea5'ea6' ea7
``When a8 is set, the actual K (ea6-3ea5+2e1
4+2ea3-3ea2 ” “at” or “a8-3”
eEL7” 2elLe + 2e, 5-3elL4+
an electromagnetic flow needle having a signal processing circuit that performs calculations such as ea3) and obtains a flow rate signal by removing an offset voltage component by cubic approximation.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP21252481A JPS58115324A (en) | 1981-12-29 | 1981-12-29 | Electromagnetic flowmeter |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP21252481A JPS58115324A (en) | 1981-12-29 | 1981-12-29 | Electromagnetic flowmeter |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS58115324A true JPS58115324A (en) | 1983-07-09 |
JPH0153403B2 JPH0153403B2 (en) | 1989-11-14 |
Family
ID=16624091
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP21252481A Granted JPS58115324A (en) | 1981-12-29 | 1981-12-29 | Electromagnetic flowmeter |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS58115324A (en) |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS57149919A (en) * | 1981-03-13 | 1982-09-16 | Yokogawa Hokushin Electric Corp | Electromagnetic flow meter |
-
1981
- 1981-12-29 JP JP21252481A patent/JPS58115324A/en active Granted
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS57149919A (en) * | 1981-03-13 | 1982-09-16 | Yokogawa Hokushin Electric Corp | Electromagnetic flow meter |
Also Published As
Publication number | Publication date |
---|---|
JPH0153403B2 (en) | 1989-11-14 |
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