JPH08304139A - Converter of mass flowmeter - Google Patents
Converter of mass flowmeterInfo
- Publication number
- JPH08304139A JPH08304139A JP10890195A JP10890195A JPH08304139A JP H08304139 A JPH08304139 A JP H08304139A JP 10890195 A JP10890195 A JP 10890195A JP 10890195 A JP10890195 A JP 10890195A JP H08304139 A JPH08304139 A JP H08304139A
- Authority
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- Prior art keywords
- time difference
- frequency
- flow tube
- flow rate
- time
- 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.)
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Links
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- Measuring Volume Flow (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、質量流量計変換器に関
し、より詳細には、フローチューブを一定振幅の固有振
動で駆動したとき、フローチューブに作用するコリオリ
の力から質量流量を求め、固有振動数から流体の密度を
求めるコリオリ流量計のドリフトを補正する質量演算器
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass flowmeter converter, and more specifically, when a flow tube is driven by a natural vibration having a constant amplitude, the mass flow rate is obtained from the Coriolis force acting on the flow tube, The present invention relates to a mass calculator that corrects the drift of a Coriolis flowmeter that obtains a fluid density from a natural frequency.
【０００２】[0002]
【従来の技術】流体工業においては、流量計測は不可欠
であり、流量計測には目的に応じた各種流量計が使用さ
れる。従来、流量計としては、主に、容積流量計，オリ
フィス，渦流量計，電磁流量計等が用いられているが、
これらは体積流量計であり、求められた体積流量から質
量流量を求める場合は、密度，温度を補正する演算を施
す必要がある。このような方式では、密度，温度の検出
誤差を伴うものであり、例えば、高価な流体を扱うファ
インケミカル用としては、近年、直接質量をコリオリ流
量計が多く用いられるようになった。2. Description of the Related Art In the fluid industry, flow rate measurement is indispensable, and various flow meters according to the purpose are used for flow rate measurement. Conventionally, as flowmeters, volumetric flowmeters, orifices, vortex flowmeters, electromagnetic flowmeters, etc. have been mainly used.
These are volumetric flow meters, and when the mass flow rate is obtained from the obtained volumetric flow rate, it is necessary to perform calculations to correct the density and temperature. In such a system, detection errors of density and temperature are involved, and for example, for fine chemicals dealing with expensive fluids, in recent years, Coriolis flowmeters with direct mass have been widely used.
【０００３】周知のように、コリオリ流量計は、被測流
体が流れるフローチューブを両端で支持し、支持された
測定管の中央部を支持線に直角な方向に交番駆動したと
き、フローチューブに質量流量に比例する位相差が生ず
ることを利用した質量流量計である。具体的には、フロ
ーチューブの両端支持部と中央部との間の対称位置に質
量流量に比例したコリオリの力による位相差信号を検出
し、位相差信号に比例した質量流量を求めるが、駆動周
波数を一定とすると、位相差信号は測定管の前記対称位
置におけるフローチューブが基準線を通過したときの時
間差信号として検出することができる。As is well known, in a Coriolis flowmeter, a flow tube through which a fluid to be measured flows is supported at both ends, and when the central portion of the supported measurement tube is alternately driven in a direction perpendicular to the support line, the flow tube is connected to the flow tube. It is a mass flow meter that utilizes the fact that a phase difference proportional to the mass flow rate occurs. Specifically, the phase difference signal due to the Coriolis force proportional to the mass flow rate is detected at the symmetrical position between the both ends of the flow tube and the central part, and the mass flow rate proportional to the phase difference signal is obtained. If the frequency is constant, the phase difference signal can be detected as a time difference signal when the flow tube at the symmetrical position of the measuring tube passes the reference line.
【０００４】フローチューブを共振周波数で交番駆動さ
せ、フローチューブの寸法，材質，被測流体の密度に応
じた一定の駆動周波数が得られ、小さい駆動エネルギで
駆動することが可能となり、駆動周波数に応じた被測流
体の密度を求めることができることから、最近では測定
管を固有振動数で駆動するのが一般的となっている。By alternatingly driving the flow tube at the resonance frequency, a constant drive frequency according to the size and material of the flow tube and the density of the fluid to be measured can be obtained, and it becomes possible to drive with a small drive energy. Since it is possible to obtain the density of the measured fluid according to the measured fluid, it has become common in recent years to drive the measuring tube at the natural frequency.
【０００５】図３は、従来の質量流量計変換器の構成を
説明するためのブロック図であり、図中、１はドライブ
回路、２は駆動コイル、３,４は検出コイル、５は位相
検出回路、６は全波整流回路、８はＣＰＵ（中央演算処
理装置）である。FIG. 3 is a block diagram for explaining the configuration of a conventional mass flowmeter converter. In the figure, 1 is a drive circuit, 2 is a drive coil, 3 and 4 are detection coils, and 5 is phase detection. A circuit, 6 is a full-wave rectifier circuit, and 8 is a CPU (Central Processing Unit).
【０００６】図３において、駆動部は、被測流体が流れ
る両端支持されたフローチューブ（図示せず）の中央部
に位置して支持体（図示せず）との間に取り付けられ、
例えば、駆動コイル２と、該駆動コイル２から磁気を受
けるコア（図示せず）等からなり、検出コイル３,４
は、フローチューブの支持部と駆動部との間の対称位置
で支持体との間に設けられ、例えば、検出コイル３,４
と磁石（図示せず）から構成される。In FIG. 3, the drive unit is located at the center of a flow tube (not shown) supported at both ends and through which a fluid to be measured flows, and is mounted between the drive unit and a support (not shown).
For example, the detection coil 3 and 4 are composed of a drive coil 2 and a core (not shown) that receives magnetism from the drive coil 2.
Is provided between the support of the flow tube and the support at a symmetrical position between the support and the drive, and, for example, the detection coils 3 and 4 are provided.
And a magnet (not shown).
【０００７】駆動コイル２は、ドライブ回路１の出力端
に接続され駆動されるが、ドライブ回路１の入力端に
は、検出コイル３で検出された正弦波信号を全波整流回
路６により整流した直流信号が接続され、検出コイル
３，全波整流回路６，ドライブ回路１，駆動コイル２か
らなる正帰還回路により、フローチューブ２の固有振動
数の正弦波発振回路が構成されている。このとき、検出
コイル３から出力されるＰ点での検出信号は、全波整流
回路６により直流電圧に変換され、ドライブ回路１にお
いて基準電圧と比較され、Ｐ点の正弦波信号ピーク電圧
が常に一定となるように制御されている。The drive coil 2 is connected to the output end of the drive circuit 1 and is driven. At the input end of the drive circuit 1, the sine wave signal detected by the detection coil 3 is rectified by the full-wave rectifier circuit 6. A DC signal is connected, and a positive feedback circuit including a detection coil 3, a full-wave rectification circuit 6, a drive circuit 1, and a drive coil 2 constitutes a sine wave oscillation circuit having a natural frequency of the flow tube 2. At this time, the detection signal at the point P output from the detection coil 3 is converted into a DC voltage by the full-wave rectifier circuit 6 and compared with the reference voltage in the drive circuit 1, and the sine wave signal peak voltage at the point P is always It is controlled to be constant.
【０００８】この結果、検出コイル４の検出電圧は、検
出コイル３の正弦波信号に対して、コリオリの力に比例
した位相差をもった一定振幅正弦波信号となり、位相差
は位相検出回路５により検出される。図４は、コリオリ
質量流量計の時間差測定の一例を説明するための図であ
る。図４（ａ）は、フローチューブの検出位置における
フローチューブの変位信号を示す図であり、検出された
正弦波信号を増幅整形して得られた台形波信号で、横軸
に時間、縦軸に電圧をとっている。図において台形ＡＢ
ＣＤ…および台形Ａ1Ｂ1Ｃ1Ｄ1…は時間軸Ｘ−Ｘに対し
電圧ピーク値の絶対値が等しく正負（±Ｅ）の電圧をも
った位相の異なるフローチューブの変位信号を示したも
ので、各々の変位信号は時間軸上連続した同形の台形波
形であり位相差時間をあらわす基準時間は、例えば、一
つの台形波形ＡＢＣＤの斜辺ＣＤのピーク値Ｃ（＋Ｅ）
あるいはＤ（−Ｅ）と、時間軸をクロスする位置Ｏとの
時間Ｔである。As a result, the detection voltage of the detection coil 4 becomes a constant amplitude sine wave signal having a phase difference proportional to the Coriolis force with respect to the sine wave signal of the detection coil 3, and the phase difference is the phase detection circuit 5. Detected by. FIG. 4 is a diagram for explaining an example of time difference measurement of the Coriolis mass flowmeter. FIG. 4A is a diagram showing a displacement signal of the flow tube at the detection position of the flow tube, which is a trapezoidal wave signal obtained by amplifying and shaping the detected sine wave signal, where the horizontal axis represents time and the vertical axis represents Is taking voltage. Trapezoid AB in the figure
CD ... and trapezoid A 1 B 1 C 1 D 1 ... Show displacement signals of flow tubes having different phases with positive and negative (± E) voltages having the same absolute value of the voltage peak value with respect to the time axis XX. Each displacement signal is a trapezoidal waveform of the same shape continuous on the time axis, and the reference time representing the phase difference time is, for example, the peak value C (+ E) of the hypotenuse CD of one trapezoidal waveform ABCD.
Alternatively, it is the time T between D (-E) and the position O crossing the time axis.
【０００９】位相の異なる前記台形ＡＢＣＤおよびＡ1
Ｂ1Ｃ1Ｄ1の変位信号において、例えば、辺ＣＤおよび
Ｃ1Ｄ1において位相差信号を説明する。四辺形ＣＣ1Ｄ1
Ｄ1は平行四辺形で、平行辺ＣＤとＣ1Ｄ1の時間差ΔＴ
は位相差信号であり、辺ＣＣ1ＤＤ1は時間軸ＯＯ1と等
しい長さを持っており、点Ｃ1およびＤ1から時間軸への
投影点を各々Ｏ2Ｏ3とすると辺Ｏ2Ｏは時間（Ｔ−Δ
Ｔ），辺ＯＯ3は時間（Ｔ＋ΔＴ）を示す。The trapezoids ABCD and A 1 having different phases
In the displacement signal of B 1 C 1 D 1, for example, describing the phase difference signal in the sides CD and C 1 D 1. Quadrilateral CC 1 D 1
D 1 is a parallelogram, and the time difference ΔT between the parallel side CD and C 1 D 1 is ΔT.
Is a phase difference signal, the side CC 1 DD 1 has a length equal to the time axis OO 1 , and the side O 2 is the projection point from the points C 1 and D 1 to the time axis O 2 O 3. O is time (T-Δ
T), side OO 3 indicates time (T + ΔT).
【００１０】時間（Ｔ−ΔＴ）は図４（ｃ）、時間（Ｔ
＋ΔＴ）は、図４（ｄ）に示すパルスで示され、時間差
ΔＴは、ＣＰＵ８において、図４（ｂ）に示す台形波一
周期の時間幅Ｍの時間パルスの２倍の時間２Ｍの間にお
ける各々のパルス幅の加算値を減算して平均を求めてい
る。例えば、 ｛４（Ｔ＋ΔＴ）−４（Ｔ−ΔＴ）｝／８＝ΔＴ …（１） により求められる。The time (T-ΔT) is shown in FIG.
+ ΔT) is shown by the pulse shown in FIG. 4D, and the time difference ΔT is in the CPU 8 during the time 2M which is twice the time pulse having the time width M of one period of the trapezoidal wave shown in FIG. 4B. The added value of each pulse width is subtracted to obtain the average. For example, it is obtained by {4 (T + ΔT) -4 (T-ΔT)} / 8 = ΔT (1).
【００１１】（１）式により求める時間差△Ｔは、誤差
が含まれていない理想条件での値である。例えば、図５
に示すように流量計測を開始するとき、流量零の状態で
は△Ｔ＝０でなければならないが、例えば、検出コイル
３,４の検出ゲインが正確に一致しないなどのため、△
Ｔ≠０であり、そのために計測する前に零点調整する必
要がある。しかし、零点調整が行われても時間経過にお
ける状態量の変化により零点が移動し、誤差要因とな
る。The time difference ΔT obtained by the equation (1) is a value under an ideal condition in which no error is included. For example, in FIG.
As shown in, when the flow rate measurement is started, ΔT = 0 must be satisfied when the flow rate is zero. However, for example, since the detection gains of the detection coils 3 and 4 do not exactly match,
Since T ≠ 0, it is necessary to adjust the zero point before measurement. However, even if the zero point adjustment is performed, the zero point moves due to a change in the state quantity over time, which causes an error.
【００１２】[0012]
【発明が解決しようとする課題】コリオリ流量計は、一
般の体積流量計と同様に、被測流体の種類，流量範囲，
温度，圧力条件等、各々異なる条件のもとでの流量計測
をしなければならない。フローチューブを共振駆動する
か固有振動数で駆動する方式のコリオリ流量計では、例
えば、被測流体の密度の相異によって振動周波数が異な
り、また、流量範囲により選ばれ、規格されたフローチ
ューブの口径，長さ等、幾何学形状の種類によっても振
動周波数が異なる。理想的なコリオリ流量計では、流体
密度が一定であり、これに伴って定められるフローチュ
ーブの固有振動数が一定であれば、計測される時間差△
Ｔが定まり、時間差△Ｔに比例した質量流量も一定に検
出できる。しかし、実際には、固有振動数が一定であっ
ても、時間差△Ｔは質量流量に比例せず、ドリフトが生
ずる。The Coriolis flowmeter is similar to a general volume flowmeter in that the type of fluid to be measured, the flow rate range,
The flow rate must be measured under different conditions such as temperature and pressure. In a Coriolis flowmeter that uses a resonance drive or natural frequency drive for the flow tube, for example, the vibration frequency varies depending on the density of the fluid to be measured, and the flow tube is selected and specified according to the flow rate range. The vibration frequency varies depending on the type of geometric shape such as the diameter and length. In an ideal Coriolis flowmeter, if the fluid density is constant and the natural frequency of the flow tube that is determined accordingly is constant, the measured time difference Δ
Since T is determined, the mass flow rate proportional to the time difference ΔT can also be detected constantly. However, actually, even if the natural frequency is constant, the time difference ΔT is not proportional to the mass flow rate, and a drift occurs.
【００１３】本発明は、ドリフトの大きさが振動周波数
に依存する値をもっていることから、ドリフト量と振動
周波数の関係に基づいて計測された時間差△Ｔに対し、
ドリフト量を補正し、理想に近い質量流量を求めること
を目的とする。In the present invention, since the magnitude of the drift has a value that depends on the vibration frequency, the time difference ΔT measured based on the relationship between the drift amount and the vibration frequency is
The purpose is to correct the drift amount and obtain a mass flow rate that is close to ideal.
【００１４】[0014]
【課題を解決するための手段】本発明は、上記課題を解
決するために、（１）被測流体が流れるフローチューブ
を離間した２点で支持し、該支持点まわりに一定振幅の
固有振動数で駆動したとき、該フローチューブに作用す
るコリオリの力を前記支持点から対称な各々の点が基準
線を通過する時間差として検知し、該時間差に比例した
質量流量を求める質量流量計変換器において、前記時間
差を求める時間差計測手段と、前記固有振動数を検知す
る周波数計測手段と、検知された固有振動数の逆数を演
算する逆数演算手段と、前記固有振動数の逆数に対応し
て予め定められたドリフト時間を記憶したドリフト時間
記憶手段と、前記時間差計測手段により求められた時間
差に対し、当該固有振動数のドリフト時間を補正し、質
量流量を算出する演算手段とからなることを特徴とす
る。In order to solve the above-mentioned problems, the present invention (1) supports a flow tube through which a fluid to be measured flows at two points separated from each other, and a natural vibration having a constant amplitude around the support point. A mass flowmeter converter for detecting the Coriolis force acting on the flow tube as a time difference when each of the symmetrical points from the support point passes a reference line when driven by a number, and for obtaining a mass flow rate proportional to the time difference. In, the time difference measuring means for obtaining the time difference, the frequency measuring means for detecting the natural frequency, the reciprocal calculating means for calculating the reciprocal of the detected natural frequency, and the reciprocal of the natural frequency in advance corresponding to The drift time of the natural frequency is corrected with respect to the time difference calculated by the time difference measuring means and the drift time storage means that stores the determined drift time, and the mass flow rate is calculated. Characterized in that comprising a calculation means.
【００１５】[0015]
【作用】フローチューブが一定振幅の固有振動で駆動さ
れるコリオリ流量計では、固有振動数が被測流体の密
度、およびフローチューブの幾何学形状によって変化
し、振動周波数に応じたドリフトが生ずる。ドリフト量
は振動周波数の逆数の関数であることが確められたの
で、このドリフト量を打消すため、振動周波数を検出し
てドリフト量と、振動周波数の関係からドリフト量を求
めて補正する。In the Coriolis flowmeter in which the flow tube is driven by the natural vibration of a constant amplitude, the natural frequency changes depending on the density of the fluid to be measured and the geometrical shape of the flow tube, causing a drift depending on the vibration frequency. Since it has been confirmed that the drift amount is a function of the reciprocal of the vibration frequency, in order to cancel this drift amount, the vibration frequency is detected, and the drift amount is obtained from the relationship between the drift amount and the vibration frequency and corrected.
【００１６】[0016]
【実施例】フローチューブの固有振動数が変化すること
により、コリオリの力に比例した時間差△Ｔにドリフト
が生ずるという現象に対して、本出願人は、時間差△Ｔ
のドリフト量Ｚｆと固有振動数ｆとの関係を調べた。EXAMPLES The applicant of the present invention has found that the time difference ΔT is caused by a change in the natural frequency of the flow tube, which causes a drift in the time difference ΔT proportional to the Coriolis force.
The relationship between the drift amount Zf and the natural frequency f was investigated.
【００１７】図１は、固有振動数と時間差△Ｔのドリフ
ト量との関係を説明するための実験結果を示した図であ
り、横軸が固有振動数ｆ、縦軸がドラフト量（時間）Ｚ
fである。FIG. 1 is a diagram showing experimental results for explaining the relationship between the natural frequency and the drift amount of the time difference ΔT, where the horizontal axis is the natural frequency f and the vertical axis is the draft amount (time). Z
f .
【００１８】図１に示す曲線は、固有振動数ｆが低周波
から高周波に向けて変化するとドリフト量Ｚfは漸時低
下し、その関係は、The curve shown in FIG. 1 shows that when the natural frequency f changes from a low frequency to a high frequency, the drift amount Z f gradually decreases.
【００１９】[0019]
【数１】 [Equation 1]
【００２０】であらわされることが確められた。It was confirmed that it can be expressed as follows.
【００２１】この関係が発生する原因は、図３に示した
ドライブ回路１の入力信号の大きさが変化しても検出コ
イル３の正弦波信号のピーク値が一定に制御され、更
に、位相検出回路５では、一定振幅の正弦波検出信号を
増幅整形して得られた、図４に示した台形波信号ＡＢＣ
Ｄは、時間軸Ｘ−Ｘに対して一定電圧（±Ｅ）の高さを
もっているから、固有振動数が変化すると、斜辺ＡＢ，
ＣＤの傾斜角が変化するが、斜辺ＡＢ，ＣＤは、正しい
直線ではなく、近似直線であることによるものと推察で
きる。The cause of this relationship is that the peak value of the sine wave signal of the detection coil 3 is controlled to be constant even if the magnitude of the input signal of the drive circuit 1 shown in FIG. In the circuit 5, the trapezoidal wave signal ABC shown in FIG. 4 obtained by amplifying and shaping the sine wave detection signal having a constant amplitude is obtained.
Since D has a height of a constant voltage (± E) with respect to the time axis XX, when the natural frequency changes, the hypotenuse AB,
Although the inclination angle of CD changes, it can be inferred that the hypotenuses AB and CD are not straight lines but approximate straight lines.
【００２２】従って、たとえば図１に示したTherefore, for example, as shown in FIG.
【００２３】[0023]
【数２】 [Equation 2]
【００２４】曲線の定数Ｋ値は一定であり、この関係か
らドリフト量を補正することが可能となる。The constant K value of the curve is constant, and the drift amount can be corrected from this relationship.
【００２５】図２は、本発明による質量流量計変換器の
回路ブロックを説明するための図で、図中、１はドライ
ブ回路、２は駆動コイル、３,４は検出コイル、５は位
相検出回路、６は全波整流回路、７は周波数計、８はＣ
ＰＵ（中央演算処理装置）、９は周波数の逆数演算部で
（以後、逆数演算部と記す）である。FIG. 2 is a diagram for explaining a circuit block of the mass flowmeter converter according to the present invention. In the figure, 1 is a drive circuit, 2 is a drive coil, 3 and 4 are detection coils, and 5 is phase detection. Circuit, 6 full-wave rectifier circuit, 7 frequency meter, 8 C
PU (Central Processing Unit), 9 is a frequency reciprocal calculation unit (hereinafter referred to as a reciprocal calculation unit).
【００２６】図２において、ドライブ回路１，駆動コイ
ル２，検出コイル３,４，位相検出回路５は、図３の場
合と同様の作用をするので、説明を省く。周波数計７
は、フローチューブの固有振動数を計測する手段である
が、実際には、前記固有振動数と同じ周波数を出力する
検出コイル３からの検出信号の周波数を計測するもの
で、検出コイル３の検出信号を整形し、得られた半周
期、又は１周期に対応した矩形波の零クロス時間をＣＰ
Ｕ８のクロック数として検知して呼び戻し、固有振動数
ｆを求めて逆数演算部９によりIn FIG. 2, the drive circuit 1, the drive coil 2, the detection coils 3 and 4, and the phase detection circuit 5 operate in the same manner as in FIG. Frequency meter 7
Is a means for measuring the natural frequency of the flow tube. Actually, it measures the frequency of the detection signal from the detection coil 3 that outputs the same frequency as the natural frequency. The signal is shaped and the zero crossing time of the rectangular wave corresponding to the obtained half cycle or one cycle is set to CP.
It is detected and recalled as the number of clocks of U8, the natural frequency f is obtained, and the reciprocal calculation unit 9 is used.
【００２７】[0027]
【数３】 (Equation 3)
【００２８】を求め、ＣＰＵ８に例えば簡略するために
ｎ＝１として記憶する。これが（２）に示すドリフト量
Ｚfとなる。Is calculated and stored in the CPU 8 as n = 1 for simplification. This is the drift amount Z f shown in (2).
【００２９】したがって、補正後の時間差Ｔｘは、 Ｔｘ＝Ｔａ−Ｚf …（３） （但し、Ｔａ：位相検出データ）（検出時間差） 更に、零点調整時のオフセットデータ値をＴoffとする
と、（３）式に加え、更にＴoffを補正することが精度
向上に寄与するので、ＣＰＵ８にＴoffを記憶しておく
ことにより、 Ｔｘ＝Ｔａ−Ｔoff−Ｚf …（４） とすることができる。[0029] Thus, the time difference Tx after correction, Tx = Ta-Z f ... (3) ( where, Ta: phase detection data) (detection time difference) Further, when the offset data value at the time of adjusting the zero point and T off, In addition to the equation (3), further correction of T off contributes to the improvement of accuracy. Therefore, by storing T off in the CPU 8, Tx = Ta−T off −Z f (4) You can
【００３０】また、（２）式は、一般式で表現すると、Further, when the expression (2) is expressed by a general expression,
【００３１】[0031]
【数４】 [Equation 4]
【００３２】（但し、Ｚａ，Ｚｂ，ＺｃはＺfの係数）
とあらわすこともでき、（５）式に従って、ドリフト量
Ｚfを補正することもできる。もちろん、（５）式は別
の表現される逆数算式であってもよい。このような考え
方により（４）式に従ってドリフト量が補正された時間
差Ｔｘに基づいて、ドリフト影響のない正確な質量流量
を求めることができる。(However, Za, Zb, Zc are coefficients of Z f )
The drift amount Z f can be corrected according to the equation (5). Of course, the expression (5) may be another expressed reciprocal expression. Based on such a concept, an accurate mass flow rate without the influence of drift can be obtained based on the time difference Tx in which the drift amount is corrected according to the equation (4).
【００３３】[0033]
【発明の効果】以上の説明から明らかなように、本発明
によれば、以下の効果がある。請求項１に対応する効
果：フローチューブを固有振動数で駆動する方式のコリ
オリ流量計においては、流量範囲により定められたフロ
ーチューブの寸法，諸元や被測流体の密度により固有振
動数が変化し、固有振動、すなわち駆動周波数に応じた
時間差信号のドリフト量が生じ、誤差となるが、ドリフ
ト量は駆動周波数の逆数の関数であることが知られたの
で、駆動周波数を検知することにより、ドリフト量の補
正が可能となり、正確な質量流量を求めることができ
る。As is apparent from the above description, the present invention has the following effects. Effect corresponding to claim 1: In a Coriolis flowmeter of a type in which a flow tube is driven at a natural frequency, the natural frequency changes depending on the size and specifications of the flow tube determined by the flow rate range and the density of the fluid to be measured. However, the natural vibration, that is, the drift amount of the time difference signal according to the drive frequency is generated, which causes an error, but since the drift amount is known to be a function of the reciprocal of the drive frequency, by detecting the drive frequency, The drift amount can be corrected, and an accurate mass flow rate can be obtained.
【図１】 固有振動数と時間差△Ｔのドリフト量との関
係を説明するための実験結果を示した図である。FIG. 1 is a diagram showing an experimental result for explaining a relationship between a natural frequency and a drift amount of a time difference ΔT.
【図２】 本発明による質量流量変換器の回路ブロック
を説明するための図である。FIG. 2 is a diagram for explaining a circuit block of the mass flow converter according to the present invention.
【図３】 従来の質量流量計変換器の構成を説明するた
めのブロック図である。FIG. 3 is a block diagram for explaining the configuration of a conventional mass flowmeter converter.
【図４】 コリオリ質量流量計の時間差測定の一例を説
明するための図である。FIG. 4 is a diagram for explaining an example of time difference measurement of a Coriolis mass flowmeter.
【図５】 従来のコリオリ流量計の零点オフセットを説
明するための図である。FIG. 5 is a diagram for explaining a zero point offset of a conventional Coriolis flowmeter.
１…ドライブ回路、２…駆動コイル、３,４…検出コイ
ル、５…位相検出回路、６…全波整流回路、７…周波数
計、８…ＣＰＵ（中央演算処理装置）、９…周波数の逆
数演算部。1 ... Drive circuit, 2 ... Drive coil, 3,4 ... Detection coil, 5 ... Phase detection circuit, 6 ... Full wave rectification circuit, 7 ... Frequency meter, 8 ... CPU (central processing unit), 9 ... Inverse frequency Arithmetic section.
Claims (1)
なくとも２点で支持し、該支持点まわりに一定振幅の固
有振動数で駆動したとき、該フローチューブに作用する
コリオリの力を位相差として検出し、位相差に比例した
時間差を計測して質量流量を求めるコリオリ流量計にお
いて、前記時間差を求める時間差計測手段と、前記固有
振動数を検出する周波数計測手段と、前記時間差に対し
検出された固有振動数の逆数を演算する逆数演算手段と
からなり、前記固有振動数に対応して零点ドリフト量を
前記時間差計測手段により求められた時間差に対し補正
することを特徴とする質量流量計変換器。1. A Coriolis force acting on a flow tube is detected as a phase difference when the flow tube through which a fluid to be measured flows is supported at at least two points and is driven around the support points with a natural frequency having a constant amplitude. Then, in the Coriolis flowmeter for measuring the mass flow rate by measuring the time difference proportional to the phase difference, the time difference measuring means for calculating the time difference, the frequency measuring means for detecting the natural frequency, and the natural frequency detected for the time difference. A mass flowmeter converter, comprising: a reciprocal number calculating means for calculating a reciprocal number of a frequency, and correcting a zero point drift amount with respect to a time difference obtained by the time difference measuring means corresponding to the natural frequency.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10890195A JP2965242B2 (en) | 1995-05-02 | 1995-05-02 | Mass flow meter converter |
| US08/455,420 US5602346A (en) | 1994-06-06 | 1995-05-31 | Mass flowmeter converter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10890195A JP2965242B2 (en) | 1995-05-02 | 1995-05-02 | Mass flow meter converter |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08304139A true JPH08304139A (en) | 1996-11-22 |
| JP2965242B2 JP2965242B2 (en) | 1999-10-18 |
Family
ID=14496507
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10890195A Expired - Fee Related JP2965242B2 (en) | 1994-06-06 | 1995-05-02 | Mass flow meter converter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2965242B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007521465A (en) * | 2003-08-29 | 2007-08-02 | マイクロ・モーション・インコーポレーテッド | Method and apparatus for correcting output information of flow measuring device |
| JP2011043515A (en) * | 2010-10-25 | 2011-03-03 | Micro Motion Inc | Method and device for correcting output information from flow rate measuring device |
-
1995
- 1995-05-02 JP JP10890195A patent/JP2965242B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007521465A (en) * | 2003-08-29 | 2007-08-02 | マイクロ・モーション・インコーポレーテッド | Method and apparatus for correcting output information of flow measuring device |
| KR101153465B1 (en) * | 2003-08-29 | 2012-06-05 | 마이크로 모우션, 인코포레이티드 | A method and apparatus for correcting output information of flow measurement apparatus |
| JP2011043515A (en) * | 2010-10-25 | 2011-03-03 | Micro Motion Inc | Method and device for correcting output information from flow rate measuring device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2965242B2 (en) | 1999-10-18 |
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