JP4112817B2 - Vibrating measuring apparatus and method for measuring fluid viscosity - Google Patents

Description

【００９３】
式（４）は実際には、１つまたは複数の測定管を励振して測定管長手軸線を中心としたねじれ振動を生じさせる測定値ピックアップの汎用手段を表している。この実施例での測定値ピックアップ１０に対しては、定数Ｋ_３の値は例えば０．２４〜０．２５の範囲で存在する。式（４）は特に、前述の形式の測定値ピックアップの動作領域内で前述のようにねじれ振動を発生させる測定管では、流体中で作用する粘性依存の摩擦力が励振電流成分Δｉ_ｅｘｃに対して半径方向で測定管長手軸線へ向かって次第にその影響を低下させるという事実を考慮している。定数Ｋ_３は実際には前述の逓減の２乗成分を表す係数である。励振電流成分Δｉ_ｅｘｃひいては摩擦測定値Ｘ_Δｉがきわめて小さな値へ向かう場合、式（４）は式（３）へ移行される。
【００９４】
式（３）または式（４）を実現するために、機能ブロック５４は、図７、図８に示された本発明の有利な実施例によれば除算器５４１を有している。この除算器は商の値Ｘ_Δｉ／Ｘ_θに対する被除数入力側と補正値Ｘ_ρ，ｆに対する除数入力側とを備えており、これにより第１の中間値が形成される。さらに機能ブロック５４は計算段５４２および乗算器５４３を有しており、計算段は第１の中間値に対する第１の入力側を備え、粘度ηに比例する第２の中間値が形成される。乗算器は第１の入力側に印加される第２の中間値を定数Ｋ_２との乗算により粘度測定値Ｘ_ηへ変換する。
【００９５】
式（３）を実現するために、計算段５４２は本発明の別の実施例によれば乗算器として構成されており、このことは図７に概略的に示されている。この乗算器は除算器５４１の出力としての第１の中間値を計算回路５４２の第２の入力側に印加される商の値Ｘ_Δｉ／Ｘ_θによって変換し、第２の中間値を得るために用いられる。
【００９６】
式（４）を実現するために、計算段５４２は本発明の別の実施例によれば、式（４）の根のなかの差に対する相応の開平器と、根を減算している項に対する相応の２乗器とを有している。さらに計算段５４２は２乗器を用いて形成される２乗値と定数Ｋ_３、Ｋ_４および補正値Ｘ_ρ，ｆとを乗算するために用いられ、これにより第２の中間値が形成される。
【００９７】
さらに上述の速度θの評価は式（１）によれば僅かではあるが流体密度ρに依存することがわかっている。これにより実際には
Ｋ_１＝Ｋ_１（ρ） （５）
が成り立つ。
【００９８】
研究により、この実施例の測定値ピックアップ１０に対しては比例係数Ｋ_１は密度依存性を考慮して次式により求められる。すなわち
Ｋ_１＝Ｋ_１，０／［１＋Ｋ_５・（Ｘ_ρ−ρ_０）］ （６）
が成り立つ。ここでρ_０は測定値ピックアップ１０のキャリブレーションに用いられるキャリブレーション用流体の調整密度または測定密度であり、Ｋ_１，０はキャリブレーション用流体を導通する測定管の比例係数であり、Ｋ_５は測定管１３の定格幅に依存するキャリブレーション定数である。
【００９９】
式（１）に類似して比例係数Ｋ_１，０について
Ｋ_１，０＝Ｘ_θ，０／Ｘ_Ｖ，０ （７）
が成り立つ。ここでＸ_θ，０はキャリブレーション用流体を導通する測定管１３の速度θを表す第１のキャリブレーション測定値であり、Ｘ_Ｖ，０はセンサ信号ｘ_ｓ１から導出された第２のキャリブレーション測定値であって、キャリブレーション用流体を導通する測定管１３のラテラル方向の偏向速度を表している。
【０１００】
式（６）は、図９に概略的に示されているように、入力段５１の機能ブロック５１４により実現される。
【０１０１】
粘度測定値Ｘ_ηの形成に利用される前述の機能ブロック５２、５３、５４、５１４および場合により乗算器５１２は、当業者に周知の手法で、例えば評価回路５０Ｂに設けられているマイクロコンピュータと相応にその内部に組み込まれて実行されるプログラムコードとにより実現される。前述の式（１）、（２）、（３）、（４）、（６）を相応の機能ブロックに変換し、式（１）、（２）、（３）、（４）、（６）の実現に用いられるマイクロコンピュータ用のプログラムコードを形成することは、当業技術者にとってはそれ自体は周知として実施されているので、ここでは詳細には説明しない。もちろんこれらの式は容易に全体またはその一部を相応に離散的に構成されたアナログおよび／またはディジタル計算回路によって評価回路５０Ｂ内で表すこともできる。相応に入力段５１も前述のマイクロコンピュータを介して実現可能であり、ここではセンサ信号ｘ_ｓ１、ｘ_ｓ２と検出された励振電流ｉ_ｅｘｃをアナログディジタル変換器によって相応のディジタル信号に変換可能であることも明らかである。これについては特に欧州特許出願公開第８６６３１９号明細書を参照されたい。
【０１０２】
この実施例による測定値ピックアップ１０では特にねじれ回転が生じ、励振電流成分Δｉ_ｅｘｃと励振電流ｉ_ｅｘｃとの比Δｉ_ｅｘｃ／ｉ_ｅｘｃは約４Ｐａｓの比較粘度に正規化される。これは９０％に達する値である。すなわち測定値ピックアップ１０は粘度ηに対して極めて高い感度を有する。
【０１０３】
また当業技術者に周知の振動タイプの他の測定値ピックアップ、例えばヘリカル形状に湾曲された測定管を有するピックアップを粘度ηの測定に使用することもできる。さらに前述したように、褶曲された測定管または湾曲された測定管を備えた振動タイプの測定値ピックアップを使用して、適切に粘度ηを測定することができる。これは例えば米国特許出願第５６４８６１６号明細書または同第５７９６０１１号明細書に記載されている。この種の測定値ピックアップは例えば比Δｉ_ｅｘｃ／ｉ_ｅｘｃを前述の比較粘度に関連して約７０％〜８０％有する。
【図面の簡単な説明】
【図１】流体用の振動式測定装置の概略図である。
【図２】図１の振動式測定装置の測定値ピックアップ１０の１つの実施例の第１の側面を示した図である。
【図３】図２の測定値ピックアップの第２の側面を示した図である。
【図４】図２の測定値ピックアップの拡大部分図である。
【図５】図１の振動式測定装置の評価回路の素子のブロック回路の形式を示す概略図である。
【図６】図５の評価回路の実施例の概略的なブロック回路図である。
【図７】図５の評価回路の実施例の概略的なブロック回路図である。
【図８】図５の評価回路の実施例の概略的なブロック回路図である。
【図９】図５の評価回路の実施例の概略的なブロック回路図である。
【符号の説明】
５０ 測定装置電子回路
１０ 測定値ピックアップ
１３ 測定管
１４ 支持フレーム
１６ 励振装置
１７、１８ センサ
１００ ケーシング[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for measuring the viscosity of a fluid guided in a pipeline and a corresponding vibration measuring device. The invention further relates to the use of a flexural vibration type Coriolis mass flow / density measuring device for measuring the viscosity of a fluid.
[0002]
[Prior art]
The Coriolis mass flow / density measuring device is preferably used to measure the mass flow and / or the density of the fluid guided in the conduit with high accuracy.
[0003]
The flexural vibration type Coriolis mass flow rate / density measuring device is a vibration measuring device as is well known, and this measuring device is designed to introduce fluid into at least one measuring tube inserted in a liquid-tight manner, in particular pressure-tight, into a pipe line. Have for. The measuring tube vibrates around a stationary state in multimode, in particular in bimode, with at least one frequency in the measuring operation. For this purpose, the measuring tube is excited by an electromechanical excitation device, usually in the first flexural vibration mode, as follows. That is, the Coriolis force is excited so as to be formed in the flowing fluid. When the measurement tube is linear, for example, the basic vibration mode of a flexible bar stretched with both sides fixed can be used as the first flexural vibration mode. This flexure bar has a single vibrating bell as is known. In particular, in a measurement tube curved in a U shape or Ω shape, the fundamental vibration mode of a bar stretched on one side is normally excited as the first flexural vibration mode.
[0004]
In this type of vibration type measuring apparatus, the second vibration mode is simultaneously excited based on the Coriolis force acting on the fluid fluid by the first flexural vibration mode. The amplitude of this second vibration mode also depends on the mass flow rate.
[0005]
In order to detect the mass flow rate, the vibration of the measuring tube at the inlet end and the vibration of the measuring tube at the outlet end are detected by corresponding sensor devices, and a first sensor signal representing the inlet vibration, It is converted into a second sensor signal representing the exit side vibration.
[0006]
Both detected vibrations have a second vibration mode superimposed on the first flexural vibration mode. This second vibration mode is a similar flexural vibration mode here, but out of phase with each other. This phase shift can accordingly be measured between the two sensor signals, and this phase shift is used as a measured quantity representing the mass flow rate in the Coriolis mass flow / density measuring device.
[0007]
In a Coriolis mass flow / density measuring device, the resonance frequency and / or the amplitude of the first flexural vibration mode usually depend measurable on the density of the fluid. Therefore, if the measurement tube is always excited at the resonance frequency of the first flexural vibration mode, this is a measure for the instantaneous density of the fluid.
[0008]
Vibrating measuring devices of the above-mentioned type, in particular Coriolis mass flow / density measuring devices, already belong to the prior art, and are described in US-A 4187721, US-A4801897, US-A4876879, US-A5648616, US-A5687100, US-A5796011, U.S. Pat. No. 6,006,609 and EP-A 866 319 describe a vibratory measuring device for measuring the mass flow rate and density of a fluid guided in a conduit. This vibration measuring device has a measurement value detector and a measuring device electronic circuit,
The measurement value detector comprises at least one measurement tube inserted in a pipe line, an electromechanical excitation device, and a sensor device responsive to lateral deflection of the measurement tube,
The measuring device electronic circuit has an excitation circuit and an evaluation circuit,
The measurement tube is stretched around the inlet end and the outlet end so as to vibrate,
And the measuring tube is vibrated relative to a stationary state by an adjustable excitation frequency during operation,
The electromechanical excitation device spatially deflects the measuring tube and at the same time deforms the measuring tube elastically,
The sensor device forms a first sensor signal representing the inlet side deflection of the measuring tube and a second sensor signal representing the outlet side deflection of the measuring tube;
The excitation circuit forms an excitation current supplied to the excitation device;
The evaluation circuit sends out a mass flow value representing the mass flow rate of the fluid and a density value representing the density of the fluid using the first sensor signal and the second sensor signal.
[0009]
Another physical parameter that is important for representing a flowing fluid is viscosity. Here, it is possible to distinguish between kinematic and dynamic as is well known.
[0010]
Viscosity and density measurement for flowing fluids Vibration measuring devices also belong to the prior art. For example, U.S. Pat. No. 4,524,610 describes a vibration measuring device for measuring the viscosity of a fluid led to a conduit, which has a measurement value detector and a measuring device electronic circuit. ,
The measurement value detector includes a linear measurement tube inserted in a pipe line, an electromechanical excitation device, and a sensor device that responds to torsion of the measurement tube,
The measuring device electronic circuit has an excitation circuit and an evaluation circuit,
The measurement tube has a measurement tube lumen for guiding a fluid, and is stretched to be able to vibrate at an inlet end and an outlet end,
The electromechanical excitation device forms a lateral deflection and / or twist in the measuring tube;
The sensor device forms a sensor signal representative of the average twist of the measuring tube;
The excitation circuit forms an excitation current supplied to an excitation device;
The evaluation circuit uses the sensor signal and the excitation current to form a viscosity measurement that represents the viscosity of the fluid.
[0011]
In this vibratory measuring device used as a density / viscosity measuring device, the measuring tube is alternately vibrated for density detection in the first flexural vibration mode described above, and for viscosity detection in the torsional vibration mode. Or simultaneously in both vibration modes but at different frequencies. Based on the torsional vibration performed by the measuring tube, a shear force is induced in the fluid, which counteracts the torsional vibration in a dampening manner.
[0012]
Further, WO-A9516897 describes a radial vibration type vibration measuring device used as a Coriolis mass flow rate / density / viscosity meter, and this measuring device measures the viscosity of a fluid guided in a pipe line. This vibration measuring device has a measurement value detector and a measuring device electronic circuit,
The measurement value detector includes a linear measurement tube inserted into a pipe line, an electromechanical excitation device, and a sensor device that responds to an axially symmetric variation of the measurement tube,
The measuring device electronic circuit has an excitation circuit and an evaluation circuit,
The measurement tube has a measurement tube lumen for guiding a fluid, and is stretched to be able to vibrate at an inlet end and an outlet end,
The electromechanical excitation device forms an axisymmetric deformation and / or a lateral deflection in the measuring tube;
The sensor device forms a sensor signal representing the deformation of the measuring tube,
The excitation circuit forms an excitation current supplied to an excitation device;
The evaluation circuit uses the sensor signal and the excitation current to form a viscosity measurement that represents the viscosity of the fluid.
[0013]
In a Coriolis mass flow / density / viscosimeter, the measuring tube is first signaled in an axisymmetric radial vibration mode to detect viscosity and mass flow. In this axially symmetric radial vibration mode, the measurement tube wall is deformed so as to remain elastic and the measurement tube centroid remains substantially statically stationary. Furthermore, the measuring tube is excited at least occasionally in the secondary vibration mode, which is used to detect the density and pressure of the fluid. The secondary vibration mode may be, for example, the first flexural vibration mode.
[0014]
WO-A9516897 describes that a radial vibration type vibration measuring device can be used for measurement of fluid mass flow rate and viscosity. However, for mass flow measurement, this device has been applied exclusively to gaseous gases. That is, the effect of viscosity damping is particularly large on the amplitude of the second vibration mode which depends on the mass flow rate, and this second vibration mode is substantially detected by the sensor at a viscosity already slightly higher than water. Can not do.
[0015]
US-A 5,359,881 further describes a method for measuring the viscosity of a flowing fluid. In this method, a flexural vibration type Coriolis mass flow / density measuring device is used to detect the mass flow rate, and additionally, a pressure difference along the flow direction in the flowing fluid is detected to detect the viscosity. .
[0016]
Furthermore, US Pat. No. 5,253,533 and US Pat. No. 6,606,609 describe flexural vibration type Coriolis mass flow / density detectors. This detector can detect the viscosity of the fluid in addition to the mass flow rate and / or density. The Coriolis mass flow / density detectors each have a linear measuring tube that is vibrated in the same torsional vibration mode simultaneously with the first flexural vibration mode during the measurement operation, thereby at least partly. Torsional vibration is performed around the longitudinal axis of the measuring tube.
[0017]
During the operation of such Coriolis mass flow measurement, until now it has been substantially detected only by the excitation current measurement, only for the compensation of the primary measurement, i.e. for the compensation of the mass flow measurement and the density measurement. Viscosity was detected incorrectly due to the output as an additional viscosity measurement.
[0018]
[Problems to be solved by the invention]
It is an object of the present invention to provide a vibration measuring device for accurately measuring the viscosity of a fluid guided in a conduit, which device is also suitable for measuring the mass flow rate and density of a fluid. Constitute. Furthermore, this invention makes it a subject to provide the method of improving the precision of the viscosity measurement using the quantity flow volume / density measuring apparatus which Coriolis knows.
[0019]
[Means for Solving the Problems]
  According to the present invention, the vibration measuring device has a measurement value detector and a measurement device electronic circuit, and the measurement value detector is inserted into the conduit and vibrates at the inlet side end and the outlet side end. At least one measurement tube stretched in a possible manner, an excitation device for forming a spatial deflection in the measurement tube, and a sensor device responsive to lateral deflection of the measurement tube, the measurement device electronics being excited Circuit and an evaluation circuit, the measuring tube has a measuring tube lumen for guiding the fluid, and laterally deflects to periodically change the spatial position of the measuring tube lumen by vibrating with respect to a stationary state during operation. Waking up, the sensor device forms a first sensor signal representative of the inlet side lateral deflection of the measuring tube and a second sensor signal representative of the outlet side lateral deflection of the measuring tube; Adjustable to form viscous friction on The excitation circuit generates an excitation current supplied to the excitation device, and the evaluation circuit determines the instantaneous mass flow rate of the fluid by the first sensor signal and the second sensor signal. A mass flow measurement value is transmitted, and the evaluation circuit uses the first sensor signal and / or the second sensor signal and an excitation current component corresponding to an attenuation amount of the excitation current due to viscous friction inside the fluid. And configured to form a viscosity measurement that represents the viscosity of the fluidThe
[0020]
The method of the present invention is a method for measuring the viscosity of a fluid guided through a pipe using a vibration measuring device,
The vibration measuring device comprises a measurement value detector (10) and a measurement device electronic circuit, the measurement value detector (10) comprising at least one measurement tube (13) inserted in a pipe line; An excitation device (16) for forming a spatial deflection in the measuring tube (13) and a sensor device (60) responsive to lateral deflection of the measuring tube;
The measuring device electronic circuit has an excitation circuit (50A) and an evaluation circuit (50B),
The measuring tube (13) is vibrated relative to a stationary position by an excitation frequency (fexc) adjustable during operation,
The sensor device (60) detects the inlet side deflection and the outlet side deflection of the measurement tube (13),
The excitation circuit (50A) forms an excitation current (iexc) supplied to the excitation device (16),
In operation, the vibration measuring device is a density measurement value (X_ρ) And an excitation frequency measurement value (Xf) representing the excitation frequency (fexc),
Vibrate the measuring tube (13) to form viscous friction in the fluid by the excitation frequency (fexc);
The excitation current (iexc) supplied to the excitation device (16) is expressed as a friction measurement value (X_Δi) And detect for the formation of
An estimate (X) representing the velocity of the fluid movement that causes the inlet and / or outlet deflection of the measuring tube (13) to produce viscous friction._θ) And detect for the formation of
Friction measurement (X_Δi) To estimate (X_θ), And the quotient value (X_Δi/ X_θ)
Correction value (X) depending on fluid density and excitation frequency (fexc)_{ρ, f}) The density measurement (X_ρ) And excitation frequency measurement (Xf),
Viscosity measurement value (X_η) To the quotient value (X_Δi/ X_θ) And correction value (X_{ρ, f}).
[0021]
DETAILED DESCRIPTION OF THE INVENTION
According to a first advantageous configuration of the vibratory measuring device according to the invention, the evaluation circuit uses the first sensor signal and / or the second sensor signal to form an estimate for the speed of movement of the fluid. Here, this fluid motion causes viscous friction.
[0022]
According to a second advantageous configuration of the vibration measuring device according to the invention, the evaluation circuit uses the excitation current to form a friction measurement representing the viscous friction in the fluid.
[0023]
According to a third advantageous configuration of the vibratory measuring device according to the invention, the evaluation circuit uses the friction value and the estimated value to form a quotient value, which is the damping of the vibration measuring tube acted on by viscous friction. Represents.
[0024]
According to the fourth configuration of the vibration type measurement apparatus of the present invention, an elastic deformation of the measurement tube lumen is generated in the measurement tube based on the spatial deflection.
[0025]
According to the fifth configuration of the vibration type measuring apparatus of the present invention, twist is generated around the longitudinal axis of the measuring tube in the measuring tube based on the spatial deflection.
[0026]
According to the sixth configuration of the present invention, the vibratory measuring device delivers a mass flow measurement value representing the instantaneous mass flow rate of the fluid.
[0027]
According to the seventh configuration of the present invention, the vibratory measuring device delivers a density measurement value representing the instantaneous density of the fluid.
[0028]
According to an advantageous first configuration of the method of the invention, the quotient value is divided by the correction value to form a viscosity measurement.
[0029]
According to an advantageous second configuration of the method of the invention, the quotient value is squared to form a viscosity measurement.
[0030]
The basic technical idea of the invention consists of the measured excitation current and the lateral direction of the measuring tube, which is always detected during operation of the described type of vibration measuring device, in particular the flexural vibration type Coriolis mass flow / density measuring device. Deriving the viscosity from the deflection, in particular the vibrations detected at the inlet and / or outlet side for mass flow measurement.
[0031]
An advantage of the present invention is that a conventional flexural vibration type Coriolis mass flow / density detector can be used for its realization, and in that case it does not need to be modified in terms of its mechanical structure. That is. Therefore, the method of the present invention can be realized in a Coriolis mass flow / density measuring apparatus that has already been used.
[0032]
【Example】
FIG. 1 schematically shows an oscillating measuring device used to detect the viscosity η of a fluid guided through a conduit (not shown), and a measured viscosity value x representing the viscosity η of the fluid._ηIs formed.
[0033]
Furthermore, the vibration measuring device advantageously determines the fluid density ρ and the mass flow rate m in addition to the viscosity η, for example, at the same time, and correspondingly these are the density measurement values X representing the density ρ._ρAnd mass flow value X representing mass flow m_mConvert to
[0034]
For this purpose, the vibration measuring device is advantageously configured as a Coriolis mass flow / density measuring device. The structure of a Coriolis mass flow / density measuring device for measuring this type of mass flow m and / or density ρ is disclosed in US Pat. Nos. 4,187,721, 4,876,879, 5,648,616, referred to at the beginning, Nos. 5687100, 5796011, and European Patent Application No. 866 319.
[0035]
In order to detect the aforementioned parameters describing the fluid, ie viscosity η, density ρ, and possibly mass flow m, the oscillating measuring device is fluid-tightly inserted (especially pressure-tight) into the conduit. It has a measured value pickup 10 of the formula.
[0036]
Furthermore, the vibration type measuring device has a measuring device electronic circuit 50 which is used for driving the measuring value pickup 10 and for forming the aforementioned measuring value. If the vibratory measuring device is designed to be coupled to a serial fieldbus in particular, the measuring device electronic circuit 50 has a corresponding communication interface for data communication so that, for example, measurement data can be stored in a higher-level memory. Sent to the program control unit or the upper process guide system. Of course, the measuring device electronics 50 can be accommodated in a correspondingly not shown electronics casing in a manner known to those skilled in the art.
[0037]
2 and 3 show an embodiment of a vibration type physical-electric conversion device used as the measurement value pickup 10. The structure of this type of conversion device is described in detail, for example, in US Pat. No. 6,006,609. Furthermore, for example, the Coriolis measurement flow rate / density measurement device “PROMASS I” series manufactured by the present applicant can be used as the aforementioned conversion device.
[0038]
The measurement value pickup 10 has a measuring tube 13 having a linear input side end 11 and an output side end 12, and this measuring tube is elastically deformable with a predetermined measuring tube inner diameter 13 A and a predetermined rating. Width. The measurement tube 13 is stretched in a rigid support frame 14 covered by the casing 100 so as to vibrate. The elastic deformation of the measuring tube inner diameter 13A here means that the fluid is conducted during the driving of the measurement pickup 10 in order to form a stress describing the fluid, ie Coriolis force, mass inertial force and / or shear force. This means that the spatial shape and / or the spatial position of the measuring tube inner diameter 13A is changed cyclically (especially periodically) as predetermined within the elastic region of the measuring tube 13. See, for example, U.S. Pat. Nos. 4,801,897, 5,648,616, 5,796,011, and / or 6,006,609. For example, a titanium alloy is particularly suitable as the material of the measuring tube 13. Instead of titanium alloys, other commonly used materials for bendable measuring tubes, such as stainless steel or zirconium, can also be used.
[0039]
The support frame 14 is fixed to the input side plate 213 covering the measurement tube 13 at the input side end 11, and is similarly fixed to the output side plate 223 covering the measurement tube at the output side end 12. ing. Further, the support frame 14 has a first support plate 24 and a second support plate 34, and these two support plates 24, 34 are fixed to the input side plate 213 and the output side plate 223. These plates are substantially parallel to the measuring tube 13, spaced from the measuring tube and spaced from each other. See FIG. 2 for this. The mutually facing sides of the two support plates 24, 34 are therefore also parallel to each other.
[0040]
A longitudinal stub 25 is preferably secured to the support plates 24, 34 at a distance from the measuring tube 13, which is used as a compensating mass that eliminates vibrations of the measuring tube 13. The longitudinal stub 25 is actually parallel to the entire length of the oscillating measuring tube 13, as shown in FIG. However, this is not necessarily so, and the longitudinal stub 25 can of course be made shorter if necessary.
[0041]
Thus, the support frame 14 with the two support plates 24, 34, the input side plate 213, the output side plate 223, and possibly the longitudinal stub 25, has a longitudinal center of gravity line. The barycentric line extends in parallel to the measurement tube longitudinal axis 13B in which the input side end 11 and the output side end 12 are virtually connected.
[0042]
2 and 3 show that the above-described support plates 24 and 34 are screwed to the input side plate 213 and the output side plate 223 by the illustrated screw head. However, other suitable fixing methods implemented by those skilled in the art may be applied to this.
[0043]
According to FIG. 2, the measured value pickup 10 further comprises an electromechanical excitation device 16. This electromechanical excitation device is used for spatially deflecting the measuring tube 13 from a stationary position during driving and elastically deforming it in a predetermined manner.
[0044]
As shown in FIG. 4, the excitation device 16 includes a T-shaped rigid lever device 15, which has a bending resistance and a bracket 154 fixed to the measuring tube. And a yoke 163. The yoke 163 is fixed to the end portion of the bracket 154 spaced from the measuring tube 13 in the same manner with bending resistance, and is oriented in the transverse direction with respect to the measuring tube longitudinal axis 13B. . As the bracket 154, for example, a metal disk that accommodates the measurement tube in the hole is used. In another suitable embodiment, an alternative lever device 15 is shown in the aforementioned US Patent Application No. 6006609.
[0045]
The lever device 15 is preferably arranged to act on the measuring tube 13 at approximately the center of the input end 11 and the output end 12, as can be seen easily from FIG. 2, so that the measuring tube 13 is in operation. On average, it has the maximum lateral deflection state.
[0046]
To drive the lever device 15, the excitation device 16 of FIG. 4 includes a first excitation coil 26 and a first permanent magnet 27 corresponding thereto, a second excitation coil 36 and a second permanent coil corresponding thereto. The two exciting coils 26 and 36 are detachably fixed to the support frame 14 below the yoke 163 on both sides of the measuring tube 13. The two excitation coils 26, 36 are electrically connected in series. However, these coils can of course be connected in parallel if necessary.
[0047]
As shown in FIGS. 2 and 4, the two permanent magnets 27 and 37 are fixed to the yoke 163 at a distance from each other. When the measurement value pickup 10 is driven, the permanent magnet 27 is mainly used as an excitation coil. The permanent magnet 37 is penetrated mainly by the magnetic field of the exciting coil 36 and moves based on the action of a corresponding electromagnetic force. For this purpose, the excitation device 16 has a unipolar or bipolar excitation current i delivered from a corresponding excitation circuit 50A of the measuring device electronic circuit 50._excThe excitation coils 26 and 36 conduct this current during driving, and correspondingly form a magnetic field, and the permanent magnets 27 and 37 move. This excitation current is likewise oscillating, with adjustable amplitude and adjustable excitation frequency f._excAnd have. Excitation current i_excFor example appears as harmonic vibration, triangular vibration or rectangular vibration. Especially the excitation current i_excOnly excitation frequency f_excCorresponds to the instantaneous mechanical resonance frequency of the measuring tube 13 that conducts the fluid, as in a conventional vibration measuring device.
[0048]
The movements of the permanent magnets 27 and 37 formed by the magnetic fields of the exciting coils 26 and 36 are transmitted to the measuring tube 13 through the yoke 163 and the bracket 154. The movement of the permanent magnets 27 and 37 is caused by the fact that the yoke 163 has a unique excitation frequency f._excAlternately to be deflected from the rest position in the direction of the support plate 24 or 34. The axis of rotation of the lever device 15 parallel to the corresponding measuring tube longitudinal axis 13B extends, for example, through the bracket 154.
[0049]
Advantageously, the support frame 14 further comprises a bearing member 29 for the electromagnetic exciter 16 detachably connected to the support plates 24, 34, which in particular will be described below with the excitation coils 26, 36 and possibly below. Used to support the individual components of the magnet support device 217.
[0050]
As described above, the excitation device 16 excites the measurement value pickup 10 when it is driven, and is used to mechanically vibrate the measurement tube 13 around the stationary position. As a result, the measuring tube generates at least a lateral deflection (oscillating deflection in the lateral direction).
[0051]
In the measurement value pickup 10 of this embodiment, the deflection in the lateral direction is simultaneously performed by the measurement tube inner diameter 13A of the measurement tube 13 fixedly stretched at the input side end portion 11 and the output side end portion 12 as described above. Generate elastic deformation. In this case, the deformation of the measuring tube inner diameter 13A actually acts over the entire length of the measuring tube 13.
[0052]
Further, the measurement tube 13 is at least partially twisted and rotated simultaneously with the lateral deflection based on the tensioned state of the measurement tube and the moment acting on the measurement tube 13 via the lever device 15. The rotation of the measuring tube 13 is performed so that the lateral deflection of the bracket end spaced from the measuring tube 13 is the same or opposite to the lateral deflection of the measuring tube 13. . In other words, the torsional vibration of the measuring tube 13 is generated in the first torsion mode corresponding to the former case, or in the second torsion mode corresponding to the latter case. At that time, in the measurement value pickup 10 of this embodiment, the natural frequency (for example, 900 Hz) of the second torsion mode is almost twice as high as that of the first mode.
[0053]
If the torsional vibration is performed only in the second torsional mode in response to the drive of the measuring tube 13, a magnet support device 217 based on the vortex principle is advantageously incorporated in the excitation device 16. This device is used in particular for adjusting and / or stabilizing the position of the axis of rotation depending on the instantaneous density of the fluid. For this reason, the magnet support device 217 guarantees that the measurement tube 13 always vibrates in the second torsion mode, and in any case, an external disturbance influence on the measurement tube 13 causes the other torsion mode (first mode) to enter. Does not cause spontaneous police box. Details of this type of magnet support device are described in detail, for example, in US Pat. No. 6,006,609. Furthermore, the use of this type of magnet support device is known from the “PROMASS I” series of measurement pickups described above.
[0054]
Advantageously for the measured value pickup 10 according to this embodiment, the excitation frequency f_excIs adjusted, and excitation is performed exclusively in the second torsion mode, and the first mode is substantially suppressed accordingly. However, if necessary, excitation can be performed in the first torsion mode.
[0055]
According to FIG. 1, the measurement value pickup 10 has a further sensor device 60, which detects the instantaneous spatial deflection of the measuring tube 13 and produces a corresponding analog signal. For this purpose, the sensor device 60 has a first sensor 17 responsive to the deflection of the measuring tube 13 causing the first lateral oscillation on the input side and the deflection of the measuring tube 13 causing the second lateral oscillation on the output side. And a second sensor 18 responsive to. As shown in FIG. 2, the two sensors 17 and 18 are fixedly arranged on the support frame 14 at a distance from each other along the measurement tube 13. These sensors are in particular arranged at the same distance with respect to the center of the measuring tube 13 and are fixedly arranged on the support frame 14, in particular on the support plate 24 or 34.
[0056]
As the sensors 17 and 18, velocity-measuring electrodynamic sensors are preferably used. However, a distance measurement type, acceleration measurement type electrodynamic sensor, or optical sensor can also be used. Of course, other deflection responsive sensors known to those skilled in the art may be used as the sensors 17,18.
[0057]
Via the sensors 17, 18, the sensor device 60 is driven by a first sensor signal x representing lateral deflection on the input side._s1And a second sensor signal x representing the lateral deflection on the output side_s2And form.
[0058]
Sensor signal x_s1, X_s2Is supplied to a programmable evaluation circuit 50B of the measuring device electronics 50 as shown in FIG. This evaluation circuit in particular has a viscosity measurement value x_ηAnd density measurement x_ρUsed to form. According to an advantageous embodiment of the invention, the evaluation circuit 50B further comprises a mass flow measurement x_mForm.
[0059]
2 measurement signals x_s1, X_s2Is the excitation frequency f_excEach having one signal frequency.
[0060]
Advantageously, the sensor device 60 further comprises an amplifier circuit, which comprises two sensor signals x._s1, X_s2Are used to adjust to the same amplitude. A suitable amplitude control circuit is shown, for example, in US Pat. No. 5,648,616 or EP-A-866319.
[0061]
Excitation frequency f_excThis adjustment is preferably performed by the phase control loop of the excitation circuit 50A, as is commonly done with this type of excitation device. The structure of this type of phase control loop and its use in adjusting the mechanical resonance frequency are described in detail in US Pat. No. 4,801,897.
[0062]
Of course, a frequency control circuit for adjusting the mechanical resonance frequency of a vibration measuring device of the above-mentioned type, known to other persons skilled in the art, may be used. See U.S. Pat. Nos. 4,524,610 and 4,801,897 for this. In addition, the use of this type of frequency control circuit for a vibration measuring device of the type described above is shown in the aforementioned “PROMASS I” series.
[0063]
Excitation current i_excFor this adjustment, a corresponding amplifier circuit is used, as is usually done with this type of vibration measuring device. This amplifier circuit has an excitation frequency f to be adjusted._excA frequency setting signal representing the excitation current i to be adjusted_excAnd an excitation current setting signal representing the amplitude of the. The frequency setting signal is, for example, a DC voltage sent from the above-described frequency control circuit, and this DC voltage has an amplitude representing a frequency.
[0064]
Excitation current i_excThe excitation circuit 50A has a corresponding amplitude control circuit that generates two sensor signals x via the instantaneous amplitude._s1, X_s2At least one of them and correspondingly constant or variable amplitude reference value W₁An excitation current setting signal is formed via In some cases, the excitation current i_excThe instantaneous amplitude of can also be used to form the excitation current setting signal. This type of amplitude control circuit is likewise well known to those skilled in the art. As an example of this type of amplitude control circuit, the “PROMASS I” series of Coriolis mass flow measuring devices is cited again. The amplitude control circuit of this measuring device is advantageously configured such that the vibration of each measuring tube is controlled to a constant amplitude, i.e. an amplitude independent of density, in the first flexural vibration mode.
[0065]
The process for determining the viscosity η of the fluid according to the present invention will be described in detail below using the example of the measurement value pickup 10 described above. Conceptual viscosity should be understood to mean both dynamic and kinematic viscosity of the fluid. This is because these viscosities can be easily converted into each other depending on the density measured in the same manner when the vibration type measuring device is driven. Further, instead of the viscosity η, the reciprocal thereof, that is, the fluidity of the fluid can be obtained.
[0066]
As described above, in the vibration type measurement apparatus including at least one measurement tube that oscillates, the spatial deflection of each measurement tube causes the movement of the fluid that generates a shearing force. The shearing force in the fluid is determined by the viscosity η of the fluid, and acts as a friction loss on the oscillating measuring tube in a damping manner.
[0067]
Excitation current i_excAnd the ratio i of the fluid motion speed θ that generates a shear force that cannot be measured directly_excIt has been found that / θ can be used as an alternative to evaluate the attenuation that acts against the deflection. Here, the attenuation of the deflection is determined together with a damping component attributed to the friction of the viscosity in the fluid, and the viscosity is determined using this. In order to determine the viscosity η accordingly, the excitation current i_excIn addition to the above, the fluid motion speed θ is also detected.
[0068]
In the process described in the aforementioned U.S. Pat. No. 4,524,610, the velocity [theta] is evaluated by the drive movement performed by the drive lever. This drive movement accordingly affects the torsional rotation of the measuring tube. This drive lever substantially corresponds to the lever device 15.
[0069]
For the purpose of viscosity measurement, the lever device 15 is only suitable for a limited range in order to detect the velocity θ via a measurement value pickup of the type described above. One reason is that, as described above, the position of the rotation axis of the lever device 15 is variable, and the actual state must always be detected accordingly. Another is that this type of lever device is often not provided at the location of a measurement value pickup of the type described above, in particular a Coriolis mass flow / density pickup.
[0070]
According to the basic idea of the present invention, therefore, the speed θ is not detected directly by the lever device 15 of the measurement value pickup 10, but the sensor signal x sent from the sensor device 60._s1, X_s2Get by.
[0071]
Sensor signal x_s1, X_s2Is used for measuring the viscosity η, the velocity θ of the fluid motion causing viscous friction, and the instantaneous lateral deflection of the measuring tube 13 reproducible at least in the operating region of the measurement value pickup 10 of the type described above. Is based on the recognition that is related to linearity. Assuming a good approximation
X_θ= K₁・ X_V                                                  (1)
Holds. Where X_VIs the sensor signal x_s1And / or x_s2, Which is a velocity measurement value derived from ## EQU3 ## instantaneously representing the lateral deflection speed of the measuring tube 13 and X_θIs an evaluation value of the velocity θ of the fluid motion, and acts on viscous friction in the fluid.₁Is a calibration measure for the proportionality factor to be obtained.
[0072]
Speed measurement X_VIs the only sensor signal x_s1Or x_s2Or two sensor signals x_s1, X_s2, Especially the sum of signals x_s1+ X_s2May be a signal value derived from (for example, instantaneous signal amplitude). The sensors 17, 18 are arranged symmetrically with respect to the center of the measuring tube 13, and the sensor signal x_s1, X_s2, Having the same signal amplitude or an equally controlled signal amplitude as described above, the signal sum x at the measurement pickup 10_s1+ X_s2Is proportional to the lateral deflection at the center of the measuring tube 13 according to this embodiment.
[0073]
Evaluation value X for speed θ_θ, The evaluation circuit 50B has an input stage 51 as schematically shown in FIGS. 5 and 6, which is the sensor signal x._s1And / or sensor signal x_s2The first measurement circuit 511 for digitally processing the speed measurement value X_VIs formed. Such a measurement circuit for measuring the signal amplitude is shown, for example, in US Pat. No. 5,648,616 or EP-A-866319.
[0074]
As schematically shown in FIG. 6, the input stage 51 further includes a multiplier 512 that is used to implement equation (1). This multiplier is a velocity measurement value X sent from the measurement circuit 511 and applied to the first input side._VAnd the proportional coefficient K applied to the second input side₁And the evaluation value X as the output_θIs sent out.
[0075]
The relationship formed by equation (1) is determined by a corresponding calibration measurement for each actual implementation of the measurement value pickup 10 and incorporated into the measurement value electronic circuit 50. Proportional coefficient K₁In the calibration measurement, for example, the actual speed of rotation at the center of the measurement tube 13 is obtained, and the sensor signal x formed simultaneously._s1And / or x_s2The relationship to is set. Proportional coefficient K₁Is numerically calculated for a series of measurement pickups, for example by the finite element method well known to those skilled in the art.
[0076]
In particular, when the fluid to be measured is a non-Newtonian fluid, the influence of the instantaneous mass flow rate on the velocity θ is evaluated as X._θShould be taken into account accordingly. That is, in a non-Newtonian fluid, the shear force decreases as the mass flow rate m increases.
[0077]
When calibrating the measurement pickup 10, typically two or more different fluids with known parameters, such as density ρ, mass flow m, viscosity η, and / or temperature, are sequentially passed through the measurement pickup 10. The corresponding measured value pickup 10 response, for example the instantaneous excitation current i_excAnd / or instantaneous excitation frequency f_excIs measured. The adjusted parameters and the response of the measured value pickup 10 each time are correspondingly interrelated, for example the proportionality factor K₁Is formed. The obtained calibration constant is stored in the table memory of the evaluation circuit 50B in the form of digital data, for example. These data are used as analog adjustment values for the corresponding calculation circuit. Here, it is pointed out that calibration of the measurement value pickup is well known to those skilled in the art, and detailed description thereof is omitted.
[0078]
The vibration of the measurement tube 13 is attenuated not only by a damping component attributed to viscous friction but also by a damping component that does not actually depend on the fluid. This damping component is caused by the frictional force and acts on the material in the excitation device 16 and the measuring tube 13, for example. In other words, the measured excitation current i_excRepresents the friction force and / or the entire friction force of the measurement value pickup 10. In determining the viscosity η of the fluid, the damping component that does not depend on the fluid is correspondingly proportional to the ratio Δi._excErased from / θ. Therefore, the excitation current i due to viscous friction_excExcitation current component Δi corresponding to the damping component of_excAnd the ratio of the velocity θ must be determined.
[0079]
Excitation current component Δi_exc, And thus the measured friction value X representing viscous friction_ΔiIn order to form the excitation current i by the input stage 51 during the driving of the vibration measuring device._excOr the corresponding no-load current measurement value K from the excitation current measurement value representing the instantaneous excitation current_i0Is subtracted. This no-load current measurement represents the aforementioned frictional force of the excitation device 16. For this purpose, the input stage 51 has a second measuring circuit 513, in particular performing digital processing, as schematically shown in FIG. 6, this measuring circuit being applied to the reduced input side. Excitation current i_excOr the no-load current measurement value K applied to the subtraction input side from the excitation current measurement value_i0Is subtracted, and the measured friction value X on the output side_ΔiIs sent out.
[0080]
No-load current measurement K_i0Similarly, during calibration of the vibration measuring device, it must be determined, for example, after the contents of the measuring tube 13 are discharged or during a period when only air is conducted, and must be stored or adjusted accordingly in the measuring device electronics 50. For those skilled in the art, the no-load current measurement K is used when necessary._i0Other physical parameters that affect the current, for example the instantaneous temperature of the measuring tube and / or the fluid_i0It is also clear that this must be taken into account during calibration.
[0081]
Damping component Δi attributed to viscous friction in fluid_excQuotient value X corresponding to / θ_Δi/ X_θThe evaluation circuit 50B further includes a first functional block 52, as shown in FIG. 5, which is a friction measurement value X applied to the dividend input side._ΔiThe evaluation value X applied to the divisor input side_θUsed to divide by.
[0082]
When the viscosity η is determined by a measurement value pickup of the type described above, the excitation current i_excIn addition to the velocity θ, the vibration frequency of the measuring tube 13 and the fluid density ρ must be taken into consideration. See U.S. Pat. No. 4,524,610 for this.
[0083]
For this purpose, the evaluation circuit 50B further comprises a second functional block 53, which is a density measurement value X._ρAnd excitation frequency measurement X_fAnd fluid density ρ and excitation frequency f_excThe corresponding correction value X depends on_{ρ, f}Is used to form
[0084]
Density measurement X_ρAnd excitation frequency X_fIs a measured value normally obtained when driving a vibration type measuring device of the above-mentioned type, particularly a Coriolis mass flow rate / density measuring device. For example, U.S. Pat. Nos. 4,187,721, 4,546,610, 4,876,879, 5,648,616, 5,687,100, or European Patent Application No. 866,139. Please refer to the book. Therefore, the measured value X is used for detecting the viscosity η of the present invention._f, X_ρIt is easily understood that can be used.
[0085]
Correction value X_{ρ, f}In particular, in the measurement tube 13 that twists and vibrates as described above, the following equation is realized by the function block 53 as a good approximation. Ie
X_{ρ, f}= X_ρ・ X_f                                              (2)
Holds.
[0086]
When distance measuring sensors are used as the sensors 17 and 18, the correction value X_{ρ, f}Simple excitation frequency measurement X to find_fInstead of its square value X_f ²Is used. That is, the functional block 53 is provided with a further multiplier or a squarer in addition to the multiplier for the equation (2).
[0087]
Quotient value X_Δi/ X_θAnd correction value X_{ρ, f}Is supplied to the third functional block 54 of the evaluation circuit 50B according to FIG._Δi/ X_θAnd correction value X_{ρ, f}Viscosity measurement value X_ηIs formed.
[0088]
According to an advantageous embodiment of the invention, the viscosity η is determined on the basis of the following equation:
[0089]
X_η= (K₂/ X_{ρ, f}) ・ (X_Δi/ X_θ)²                      (3)
Where K₂Is a constant determined by calibration, particularly a constant depending on the square of the rated width of the measuring tube 13.
[0090]
Viscosity measurement value X determined by equation (3)_ηIt has been found that the smaller the viscosity η and / or the higher the fluid density ρ, the more accurately matches the actual viscosity η. Further, in the embodiment of the present invention, the viscosity η can be accurately obtained as the rated width of the measuring tube 13 increases.
[0091]
According to another advantageous embodiment of the method of the invention, an accurate viscosity measurement X_ηIn particular, when the viscosity η is larger than 5 Pas (= Pascal second) and / or when the rated width of the measuring tube 13 is smaller than 8 mm, detection is performed based on the following equation.
[0092]
[Expression 1]

[0093]
Equation (4) actually represents a universal means of measurement value pickup that excites one or more measurement tubes to produce torsional vibration about the measurement tube longitudinal axis. For the measured value pickup 10 in this embodiment, a constant K₃The value of exists in the range of 0.24 to 0.25, for example. In particular, in the measurement tube that generates the torsional vibration as described above in the operation range of the measurement value pickup of the above-described type, the equation (4) indicates that the viscous-dependent frictional force acting in the fluid causes the excitation current component Δi._excIn contrast, the fact that the influence is gradually reduced in the radial direction towards the longitudinal axis of the measuring tube is taken into account. Constant K₃Is a coefficient that actually represents the square component of the above-mentioned decrease. Excitation current component Δi_excAs a result, measured value X of friction_ΔiIs going to a very small value, equation (4) is transferred to equation (3).
[0094]
In order to implement equation (3) or equation (4), the functional block 54 comprises a divider 541 according to the preferred embodiment of the invention shown in FIGS. This divider is the quotient value X_Δi/ X_θDividend input and correction value X for_{ρ, f}And a divisor input side for the first intermediate value. Furthermore, the functional block 54 comprises a calculation stage 542 and a multiplier 543, the calculation stage having a first input for the first intermediate value and forming a second intermediate value proportional to the viscosity η. The multiplier uses the second intermediate value applied to the first input side as a constant K₂Viscosity measurement value X_ηConvert to
[0095]
To implement equation (3), the calculation stage 542 is configured as a multiplier according to another embodiment of the present invention, which is schematically illustrated in FIG. This multiplier uses the first intermediate value as the output of the divider 541 as the quotient value X applied to the second input side of the calculation circuit 542._Δi/ X_θIs used to obtain a second intermediate value.
[0096]
To implement equation (4), calculation stage 542, according to another embodiment of the present invention, for the corresponding square root for the difference in roots of equation (4) and the term subtracting the roots. And a corresponding squarer. Further, the calculation stage 542 is a square value formed by using a squarer and a constant K.₃, K₄And correction value X_{ρ, f}Are used to form a second intermediate value.
[0097]
Furthermore, it is known that the evaluation of the velocity θ described above depends slightly on the fluid density ρ according to the equation (1). This actually
K₁= K₁(Ρ) (5)
Holds.
[0098]
Research has shown that the proportionality factor K is used for the measured value pickup 10 of this embodiment.₁Is obtained by the following equation in consideration of density dependency. Ie
K₁= K_{1, 0}/ [1 + K₅・ (X_ρ−ρ₀]] (6)
Holds. Where ρ₀Is the adjustment density or measurement density of the calibration fluid used for calibration of the measurement value pickup 10, and K_{1, 0}Is the proportional coefficient of the measuring tube that conducts the calibration fluid, and K₅Is a calibration constant depending on the rated width of the measuring tube 13.
[0099]
Similar to equation (1), proportional coefficient K_{1, 0}about
K_{1, 0}= X_{θ, 0}/ X_{V, 0}                                      (7)
Holds. Where X_{θ, 0}Is a first calibration measurement value representing the velocity θ of the measurement tube 13 through which the calibration fluid is conducted, and X_{V, 0}Is the sensor signal x_s1Is a second calibration measurement value derived from, and represents the lateral deflection speed of the measurement tube 13 that conducts the calibration fluid.
[0100]
Equation (6) is implemented by the function block 514 of the input stage 51, as schematically shown in FIG.
[0101]
Viscosity measurement value X_ηThe above-described functional blocks 52, 53, 54, 514 and possibly the multiplier 512 used in the formation of are formed in a manner well known to those skilled in the art, for example, in accordance with a microcomputer provided in the evaluation circuit 50B. The program code is implemented and executed. The above equations (1), (2), (3), (4), (6) are converted into corresponding functional blocks, and the equations (1), (2), (3), (4), (6) The formation of the program code for the microcomputer used for realizing the above is well-known to those skilled in the art and will not be described in detail here. Of course, these equations can easily be represented in the evaluation circuit 50B by analog and / or digital calculation circuits which are configured in a discrete manner in whole or in part. Correspondingly, the input stage 51 can also be realized via the aforementioned microcomputer, here the sensor signal x_s1, X_s2And the detected excitation current i_excIt is clear that can be converted into a corresponding digital signal by an analog-digital converter. Reference is made in particular to EP-A 866 319 in this regard.
[0102]
In the measurement value pickup 10 according to this embodiment, torsional rotation occurs in particular, and the excitation current component Δi_excAnd excitation current i_excThe ratio Δi to_exc/ I_excIs normalized to a comparative viscosity of about 4 Pas. This is a value that reaches 90%. That is, the measured value pickup 10 has a very high sensitivity to the viscosity η.
[0103]
It is also possible to use other measurement value pickups known to those skilled in the art for measuring the viscosity η, for example a pickup with a measuring tube curved in a helical shape. Further, as described above, the viscosity η can be appropriately measured by using a vibration type measurement value pickup having a curved measurement tube or a curved measurement tube. This is described, for example, in US Pat. Nos. 5,648,616 or 5,796,011. This kind of measured value pickup is for example the ratio Δi_exc/ I_excAbout 70% to 80% in relation to the aforementioned comparative viscosity.
[Brief description of the drawings]
FIG. 1 is a schematic view of a vibration measurement device for fluid.
FIG. 2 is a view showing a first side surface of one embodiment of a measurement value pickup 10 of the vibration type measurement apparatus of FIG. 1;
FIG. 3 is a diagram showing a second side surface of the measurement value pickup shown in FIG. 2;
FIG. 4 is an enlarged partial view of the measurement value pickup of FIG. 2;
5 is a schematic diagram showing the format of a block circuit of elements of the evaluation circuit of the vibration type measuring apparatus of FIG. 1. FIG.
6 is a schematic block circuit diagram of an embodiment of the evaluation circuit of FIG.
7 is a schematic block circuit diagram of an embodiment of the evaluation circuit of FIG.
8 is a schematic block circuit diagram of an embodiment of the evaluation circuit of FIG.
FIG. 9 is a schematic block circuit diagram of an embodiment of the evaluation circuit of FIG.
[Explanation of symbols]
50 Measuring device electronic circuit
10 Measurement pickup
13 Measuring tube
14 Support frame
16 Exciter
17, 18 sensor
100 casing

Claims (25)

In a vibration type measuring apparatus for measuring the mass flow rate and viscosity of a fluid guided in a pipeline,
The vibration measurement device has a measurement value detector (10) and a measurement device electronic circuit (50),
The measurement value detector (10) includes at least one measurement tube (13) that is inserted into a pipe and is oscillated between an inlet-side end and an outlet-side end, and the measurement tube (13). An excitation device (16) for forming a spatial deflection on the sensor and a sensor device (60) responsive to lateral deflection of the measuring tube (13),
The measuring device electronic circuit (50) has an excitation circuit (50A) and an evaluation circuit (50B),
The measuring tube (13) has a measuring tube lumen (13A) for guiding a fluid and vibrates in a stationary state during operation to periodically change the spatial position of the measuring tube lumen (13A). Woke up
The sensor device (60) includes a first sensor signal (x _s1 ) representing the inlet side lateral deflection of the measuring tube (13) and a second sensor representing the outlet side lateral deflection of the measuring tube (13). Signal (x _s2 ),
In operation, the measuring tube (13) is vibrated relative to the rest position by an adjustable excitation frequency (f _exc ) to create viscous friction in the fluid,
The excitation circuit (50A) forms an excitation current (i _exc ) supplied to the excitation device (16),
The evaluation circuit (50B) sends a mass flow measurement value (X _m ) representing the instantaneous mass flow rate of the fluid by means of the first sensor signal (x _s1 ) and the second sensor signal (x _s2 ),
The evaluation circuit (50B) corresponds to the first sensor signal (x _s1 ) and / or the second sensor signal (x _s2 ) and the amount of attenuation caused by viscous friction inside the fluid among the excitation current (i _exc ). A vibration measurement apparatus that forms a viscosity measurement value (X _η ) representing the viscosity of a fluid using an excitation current component (Δi _exc ). The evaluation circuit (50B) uses the first sensor signal (x _s1 ) and / or the second sensor signal (x _s2 ) to form an estimate (X _θ ) for the speed of motion acting on the viscous friction of the fluid. The vibration type measuring apparatus according to claim 1. The vibration measurement device according to claim 1, wherein the evaluation circuit (50B) uses the excitation current (i _exc ) to form a friction measurement value (X _Δi ) representing the viscous friction of the fluid. The evaluation circuit (50B) forms a quotient value (X _Δi / X _θ ) using the measured friction value (X _Δi ) and the estimated value (X _θ ),
4. The vibration type measuring device according to claim 2, wherein the quotient value represents an attenuation amount of the vibration measuring tube (13) caused by viscous friction.   2. The vibration type measuring device according to claim 1, wherein an elastic deformation of the measuring tube lumen (13A) is formed in the measuring tube (13) based on the spatial deflection.   6. A vibratory measuring device according to claim 5, wherein a torsion is formed in the measuring tube (13) about the longitudinal axis of the measuring tube (13B) based on its spatial deflection. Measuring tube during operation is vibrating with respect to the stationary state at an adjustable excitation frequency _{(f exc),} the excitation frequency from the evaluation circuit _{(50B) (f exc)} and the correction value that depends on the fluid density (X _{ρ, f)} is The vibration type measuring device according to any one of claims 1 to 6, wherein the measurement value (X _η ) is sent and the viscosity measurement value (X _η ) is formed by the correction value (X _{ρ, f} ). The vibration type measuring apparatus according to claim 1, wherein a density measurement value (X _ρ ) representing an instantaneous density of the fluid is sent out. The evaluation circuit (50B) sends an excitation frequency measurement value (X _f ) representing an excitation frequency (f _exc ) that vibrates the measurement tube (13), and the excitation frequency measurement value (X _f ) and density measurement value (X _9. The vibration type measuring apparatus according to claim 8 , wherein the viscosity measurement value (X [ _eta] ) is formed using the correction value (X [ _{rho], f} ) determined based on [ _rho] ). Evaluating circuit (50B) to form an estimate for the velocity of motion acting on the viscous friction of the fluid with at least one sensor signal _{(x s1, x s 2)} (X θ), of claims 1 to 9 The vibration type measuring apparatus according to any one of the above. Evaluating circuit (50B) is formed viscosity measured value (X _eta) based on at least one of the signal amplitude derived from the sensor signal _{(x s1,} x _s2), any one of claims 1 to 10 Vibration type measuring device. The evaluation circuit (50B) _obtains the attenuation amount of the vibration of the measuring tube (13) acting on the viscous friction by using at least one sensor signal (x _s1 , x _s2 ) and the excitation current (i _exc ). based on the attenuation form viscosity value representing the viscosity of the fluid _(X η), the vibration-type measuring device according to any one of claims 1 to 11. Evaluating circuit (50B) is formed of friction measured value representative of the viscous friction of the fluid (X _.DELTA.i) using an excitation current _{(i exc),} the vibration-type measuring device according to any one of claims 1 to 12. The evaluation circuit (50B) uses the excitation current (i _exc ) to form a friction measurement value (X _Δi ) representing the viscous friction of the fluid, and further uses the friction measurement value (X _Δi ) and the estimated value (X _θ ). The vibration-type measuring device according to claim 13 , wherein a quotient value (X _Δi / X _θ ) is formed, and the quotient value represents a damping amount of the vibration measuring tube (13) caused by viscous friction. The vibration type measuring device according to any one of claims 1 to 14 , wherein an elastic deformation of the measurement tube lumen (13A) is formed in the measurement tube (13) that vibrates laterally with respect to a stationary state. . Twisting the measuring tube (13) within the vibration is formed in the central flow tube longitudinal axis (13B), the vibration-type measuring device according to any one of claims 1 to 15. Fluid partially torsional vibration mode measurement tube axis during operation to form a viscous friction (13B) as the center of the measuring tube (13) is formed, of any one of claims 1 to 16 Vibration measuring device. Sensor device (60) has a first sensor responsive to deflection of the inlet side of the lateral of the measuring tube (13) (17), the sensor sends out at least one signal, from the claims 1-17 The vibration type measuring apparatus according to any one of the above. Sensor device (60) has a sensor (18) a second responsive to the deflection of the outlet side of the lateral of the measuring tube (13), the sensor sends out at least one signal, from the claims 1 18 The vibration type measuring apparatus according to any one of the above. The vibration type measuring device according to any one of claims 1 to 19 , wherein the measuring tube (13) is configured in a straight line. Measuring tube (13) is bent, the vibration-type measuring device according to any one of claims 1 to 20. The vibration type measuring device according to any one of claims 1 to 21 , wherein the evaluation circuit (50B) sends out a mass flow rate measurement value (Xm) representing an instantaneous mass flow rate of the fluid. A method for measuring the viscosity of a fluid guided in a pipeline using a vibration measuring device,
The vibration measuring device has a measurement value detector (10) and a measuring device electronic circuit,
The measurement value detector (10) comprises at least one measurement tube (13) inserted in a conduit, an excitation device (16) for forming a spatial deflection in the measurement tube (13), and the measurement A sensor device (60) responsive to lateral deflection of the tube;
The measuring device electronic circuit has an excitation circuit (50A) and an evaluation circuit (50B),
The measuring tube (13) is vibrated relative to a stationary position by an excitation frequency (f _exc ) adjustable during operation,
The sensor device (60) detects the inlet side deflection and the outlet side deflection of the measuring tube (13),
The excitation circuit (50A) forms an excitation current (i _exc ) supplied to the excitation device (16),
The vibration type measuring device is of a type that sends a density measurement value (X _ρ ) representing the density of the fluid and an excitation frequency measurement value (X _f ) representing the excitation frequency (f _exc ) during operation.
Oscillating the measuring tube (13) with the excitation frequency (f _exc ) to form viscous friction in the fluid;
An excitation current (i _exc ) supplied to the excitation device (16) is detected for the formation of a friction measurement (X _Δi ) representing viscous friction;
Detecting the inlet-side and / or outlet-side deflection of the measuring tube (13) for the formation of an estimate (X _θ ) representing the speed of fluid movement causing viscous friction;
Friction measured values (X _.DELTA.i) divided by the estimated value (X _θ), formed quotient value representing the attenuation of the vibration measurement tube caused by viscous friction _(X Δi _/ X _θ),
A correction value (X _{ρ, f} ) that depends on the density of the fluid and the excitation frequency (f _exc ) is formed using the density measurement value (X _ρ ) and the excitation frequency measurement value (X _f ),
A method of forming a measured viscosity value (X _η ) representing a viscosity by using a quotient value (X _Δi / X _θ ) and a correction value (X _{ρ, f} ). 24. The method according to claim 23 , wherein the quotient value (X [Delta] _i / X [ _theta] ) is divided by the correction value (X [ _{rho], f} ) to form a viscosity measurement (X [ _eta] ). 24. The method of claim 23 , wherein the quotient value (X [Delta] _i / X [ _theta] ) is squared to form a viscosity measurement (X [ _eta] ).

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