DE102007049242A1 - Vibration-type meter and method of operating such - Google Patents

Abstract

The The invention relates to a vibration type measuring device Measuring at least one process variable, in particular a mass flow, a density, a viscosity, a pressure or the like, in particular in one of a medium permeable process line comprising at least one Sensor, which one of the process size can be influenced measurable signal, where by the meter determined measured value of the process variable from a Functional relationship in connection with measuring parameters from the measuring signal can be determined, and wherein the measurement parameters a temperature-dependent Cross-sensitivity with regard to the temperature distribution have in the meter. The meter includes at least one temperature sensor, over which the local Temperature measurable and subsequently with electronic means Temperature distribution field by means of a temperature distribution theorem is calculable, and that from the temperature field data correction values for compensation of the temperature-dependent cross-sensitivities the measurement parameters can be determined.

Description

The The invention relates to a measuring device of the vibration type and a method of operating such, according to the preamble of claims 1 and 7.

generic Measuring devices are known to be used for Measuring at least one process variable, in particular a mass flow, a density, a viscosity, a pressure or the like, in particular in one of a medium permeable process line. They include at least a sensor, which one of the process size can be influenced measurable signal, where by the meter Determined measured value of the process variable from a functional context Can be determined from the measuring signal in conjunction with measuring parameters is, and wherein the measurement parameters, a temperature-dependent cross-sensitivity with regard to the temperature distribution in the measuring device exhibit. A concrete example of a generic Meter is a known in principle Coriolis flowmeter.

The mass flow q and the mass density rho of a medium can be determined by means of a Coriolis flowmeter. In this case, (at least) a pipe through which the medium flows is excited to oscillate in (at least) one eigenmode having the natural frequency f, and the temporal phase shift dt of the oscillation deflection between two symmetrical points of the through-flowed pipe is measured. The mass flow rate q can then be determined from the measurement signal of the phase shift dt by means of q = K (dt - d0) and the density rho of the medium results from the frequency f rho = rho0 + W / (f 2 ).

The above-mentioned functional relationships for the determination of Measured values density rho and mass flow q comprise the measuring parameters d0 (Zero point phase), rho0 (density offset), K (flowmeter constant), W (density variation parameter).

The Zero point phase d0, the density offset rho0 and in particular also the so-called flow-meter constant K and the density variation parameter W are not independent of those in general different temperatures of the individual components or spatial Segments of the meter.

The means that, for example, due to temperature-induced Tension or material property changes each one this parameter is a functional of the spatial temperature distribution in the measuring device d0 = F1 [T (x, y, z)], rho0 = F2 [T (x, y, z)], K = F3 [T (x, y, z)] and W = F4 [T (x, y, z)].

The The problem therefore lies in the cross-sensitivity of the flow and the density measurements with respect to the spatial Temperature distribution T (x, y, z) or after appropriate discretization with respect to a corresponding amount of temperature values [T1, T2, ..., Tn].

These Cross-sensitivity can indeed be determined by means of a Measurement of temperatures T1, T2, ..., Tn and knowledge of the functional Dependence of the parameters d0 = f (T1, T2, ..., Tn), rh0 = f (T1, T2, ..., Tn), etc., but requires a corresponding extensive temperature measurement.

From the WO 04053428 is known method and a device that makes the consideration of recorded in the past temperature values, that records a kind of temperature history.

This But takes only one aspect, namely the monitoring whether it is possible to influence the measured value locally if necessary from a temperature shift results.

Consequently is the detection and derivation of temperature dependencies in this case only inadequate, if necessary falsifying.

Of the Invention is therefore the object of a meter of the generic type and a method for Operation of such a further develop that cross-sensitivities also Compensated for a temperature distribution in the meter are. In particular, for example, temperature-induced voltages or Material property changes throughout the device be considered.

The asked task is in a generic Measuring device by the characterizing features of the claim 1 and with regard to a method of the generic Type according to the invention by the characterizing Characteristics of claim 7 solved.

Further advantageous embodiments of the measuring device are in the dependent claims 2 to 6, and further advantageous Embodiments of the method are in the dependent claims 8 to 13 indicated.

Further advantageous embodiments are dependent on the others Claims specified.

One The measuring device according to the invention thus comprises at least one temperature sensor, over which the local Temperature measurable and subsequently with electronic means Temperature distribution field by means of a temperature distribution theorem is calculable, with turkorwerte from the temperature field data correction for compensation of the temperature-dependent cross-sensitivities the measurement parameters can be determined.

at a preferred embodiment as a Coriolis flowmeter is according to the invention at least one place of the Coriolis flowmeter or meter Temperature sensor placed over which the local Temperature measurable and subsequently with electronic means Temperature distribution field from a temperature distribution theorem is calculable, which corresponds to the evaluation unit.

The then determined temperature distribution field then determined, for example purely temperature-induced local deflections or dilatations, which are subtracted from the measured value, so that only the flow-dependent Measured value corrected for temperature disturbances.

According to one In another advantageous embodiment, the temperature field determination unit is constructional integrated into the evaluation unit.

In According to a further advantageous embodiment, the temperature distribution theorem the analytic or numerical solution of the partial differential equations the heat dissipation in the meter, where the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) a location dependence corresponding to the meter having.

In a further advantageous embodiment of the invention the temperature distribution theorem the analytical or numerical Solution of ordinary differential equations, the thermal propagation modeled via a thermal network describe in the device.

In a further advantageous embodiment of the invention takes place the determination of the current temperature distribution field from the Temperature distribution theorem taking into account past temperature readings and / or past calculated temperature distributions.

core the inventive method for operating a Measuring device of the vibration type, in particular a Coriolis Duchflussmessgerätes is it, that at least one point of the measuring tube or measuring device a temperature sensor is placed over which the measured local temperature and subsequently a temperature distribution field is calculated from a temperature distribution theorem, and that from the temperature field data correction data for the compensation of Temperature-dependent cross-sensitivities are determined.

A advantageous embodiment of an inventive The method is characterized in that the temperature distribution theorem analytical or numerical solution of the partial differential equations the heat propagation in the meter comprises, wherein the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) a location dependence corresponding to the meter having.

wobei die Volumenwärmekapazität c(x, y, z) und die Wärmeleitfähigkeit k(x, y, z) dann eine dem Gerät entsprechende Ortsabhängigkeit aufweist.A further advantageous embodiment of a method according to the invention is characterized in that, with the following formal relationship, the temperature distribution field is determined by electronic calculation of an analytical or numerical solution of the partial differential equations of heat propagation in the device, by determining the heat equation for the temperature distribution T (x, y , z; t)

wherein the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) then has a location dependence corresponding to the device.

A further advantageous embodiment of a method according to the invention is characterized in that the temperature distribution takes place under the boundary conditions such that: T (x ^ 2 + y ^ 2 = r, 0 <z <l) = T _M (t). Ie. the tube with the radius r and the length l has everywhere the time-dependent medium temperature.

A further advantageous embodiment of an inventive Method is characterized in that the temperature distribution theorem the analytical or numerical solution of ordinary Differential equations that are over a thermal network describe modeled heat propagation in the device, includes.

A further advantageous embodiment of an inventive Method is characterized in that additionally for temperature measurement or for temperature field distribution also past Temperature readings and / or past calculated Temperature distributions are taken into account. By Time correlation are convection, heat conduction etc to determine. This fully describes the temperature distribution field.

A further advantageous embodiment of an inventive Method is characterized in that from the temperature field data correction data be determined, from which an amplitude correction takes place, in such a way that only the relevant temperature-corrected amplitude values be used to determine the flow.

to Implementation of a method according to the invention in a measuring device according to the invention also provided corresponding electronic computing means.

It be in a measuring device according to the invention So only a few places (in extreme cases, only one) in the device or in the medium or in the device environment temperature measurements and / or heat flow measurements performed.

Out the knowledge of these measured values at a time t_m and the knowledge (or a suitable assumption) about the spatial Temperature distribution T (x, y, z) or via a set [T1, T2, ..., Tn] of different segments of the device prevailing temperatures at the time t_m is by means of a suitable mathematical model of the spatial temperature distribution T (x, y, z) or the set [T1, T2, ..., Tn] of in different Segments of the device prevailing temperatures to one Calculated time t_m + 1.

As well If necessary, you can also use the mathematical model Waremeenergiedichten [w1, w2, ... wn] or heat flows [J1, J2, ..., Jn] calculated at any position in the unit become.

In order to is it possible, the cross-sensitivity of any parameter P of the flux or density calculation (eg K or rho0) is not only with respect to measured temperatures or heat flows but also with regard to additional calculated Temperature values, thermal energy densities or heat flows herauszurechnen.

The mathematical model or the associated algorithm is characterized in that it or he from the measured values [TM1, ..., TMi, JM1, ..., JMi] (t_m) and the values [T1, ..., Tn, w1, ... wn, J2, ..., Jn] (t_m) the values [T1, ..., Tn, w1, ... wn, J2, ..., Jn] (t_m + 1).

• 1. dem analytischen oder numerischen Lösen der partiellen Differentialgleichungen, die die Wärmeausbreitung im Gerät durch z. B. ärmeleitung, Konvektion oder Strahlungstransport beschreiben. Die zu lösende Wärmeleitungsgleichung für die Temperaturverteilung T(x, y, z, t) im Gerät würde z. B.
  
  lauten, wobei die Volumenwärmekapazität c(x, y, z) und die Wärmeleitfähigkeit k(x, y, z) dann eine dem Gerät entsprechende Ortsabhängigkeit aufweisen würden. Eine Randbedingung für die Temperaturverteilung könnte dann beispielsweise T(x^2 + y^2 = r,0 < z < l) = T_M(t) lauten. D. h. das Rohr mit dem Radius r und der Länge l besitzt überall die zeitabhängige Mediumstemperatur T_M(t);
• 2. dem analytischen oder numerischen Lösen der gewöhnlichen Differentialgleichungen, die die über ein thermisches Netzwerk modellierte Wärmeausbreitung im Gerät beschreiben;
• 3. einer wie auch immer (empirisch, mittels eines physikalischen Modells, mittels eines neuronalen Netzwerkes, statistisch, ...) gewonnen Berechnungsvorschrift (d. h. einer Funktion) B{...} mit [T1, ..., Tn, w1, ...wn, J2, ..., Jn](t_m + 1) = B{[T1, ..., Tn, w1, ...wn, J2, ..., Jn](t_m); [TM1, ..., TMi, JM1, ..., JMi](t_m)}.

The mathematical model or the algorithm can, for example, consist of:

• 1. the analytical or numerical solution of the partial differential equations, the heat dissipation in the device by z. As describe conduction, convection or radiation transport. The heat equation to be solved for the temperature distribution T (x, y, z, t) in the device would z. B.
  
  The volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) would then have a location dependency corresponding to the device. A boundary condition for the temperature distribution could then be, for example, T (x ^ 2 + y ^ 2 = r, 0 <z <l) = T _M (t). Ie. the tube with the radius r and the length l everywhere has the time-dependent medium temperature T _M (t);
• 2. the analytical or numerical solution of the ordinary differential equations describing the thermal propagation modeled by a thermal network in the device;
• 3. a calculation rule (ie, a function) B {...} obtained with [T1, ..., Tn, w1, whatever, empirically, by means of a physical model, by means of a neural network, statistically, ...] ... wn, J2, ..., Jn] (t_m + 1) = B {[T1, ..., Tn, w1, ... wn, J2, ..., Jn] (t_m); [TM1, ..., TMi, JM1, ..., JMi] (t_m)}.

at the calculation of the mass flow or the mass density to a Time t can then close the cross sensitivities with respect to a suitable subset of the measured and calculated temperatures, heat flows, etc. {[TM1, ..., TMi, JM1, ..., JMi] (t); [T1, ..., Tn, w1, ... wn, J2, ..., Jn] (t)} be considered at time t.

• 1) Flußmeterkonstante K = f_K(TM, TM2, JM7, T1, T2, w8) und f_K(...) ist eine geeignete mathematische Funktion.
• 2) Massendurchfluß Q = f_Q(dt, TM1, TM2, T1) und f_Q(...) ist eine geeignete mathematische Funktion der gemessenen Phasenverschiebung dt und den gemessenen bzw. berechneten Temperaturen.

Examples for this are:

• 1) Flow-rate constant K = f_K (TM, TM2, JM7, T1, T2, w8) and f_K (...) is a suitable mathematical function.
• 2) Mass flow Q = f_Q (dt, TM1, TM2, T1) and f_Q (...) is a suitable mathematical function of the measured phase shift dt and the measured or calculated temperatures.

The Invention is described below with reference to an embodiment described in more detail.

The only 1 shows schematically the interaction of the components of a device according to the invention.

In the area of the measuring tube 1 is a temperature sensor 2 arranged.

The value measured there is in electronic means 3 read, here referred to as temperature field determination unit. Therein, according to the specified theorem, a temperature field, ie the distribution of the temperature along the entire measuring tube, is calculated from the temperature value measured only at one point.

These determined distribution data then go in the evaluation within the evaluation 4 with a.

In the evaluation unit 4 also the measuring signals of the sensors 6 captured and processed. The sensors 6 are, for example, electrodynamically operating displacement sensors, which are the vibrations of the measuring tube 1 at the inlet and at the outlet. In the evaluation unit 4 is the phase shift dt of the measured signals and then determined taking into account the flow meter constant K and the zero point phase d0 mass flow q.

Corrections of the cross-sensitivity of the mentioned parameters flux-meter constant K and zero-point phase d0 are in the evaluation unit 4 based on the determined temperature distribution values in the manner shown above.

The temperature-corrected flow value will then be shown on the display 5 played.

In this case, an embodiment may consist of a modeling as a thermal network, consisting of the three components tube, end plate and frame with the respective temperatures T _tube , T _plate and T _{Hou sin g} : measured only the temperatures T _T and T _H , while the Temperature of the end plate T is calculated.

It is assumed that the current J _{1 of} the heat energy from the pipe into the end plate is proportional to the temperature difference J 1 = (T T - T P ) / R 1 and correspondingly, the current J _{2 of} the heat energy from the end plate into the housing in proportion to the temperature difference J2 = (T P - T H ) / R 2 is. Since the temperature of the end plate T _{P is} proportional to the heat energy stored in the plate T P = W P / C is and their temporal change (ẋ: = dx / dt) again by the sum of the heat inflows and outflows W P = J 1 - J 2 is given, it finally follows the differential equation T P = -T P / τ + T T / CR 1 + T H / CR 2 for the temperature of the plate, with the characteristic time τ = C / (1 / R 1 + 1 / R 2 ).

From the temperature measured values T _T (t) and T _H (t) it is possible with the aid of the above differential equation to calculate the temperature T _P (t) for known (for example experimentally determined) values of the constants R ₁ , R ₂ and C.

For this, suppose that at some initial time t = 0, the temperature T _P (0) equals the temperature of the stationary solution T P (0) = τ (T T (0) / CR 1 + T H (0) / CR 2 ) is, and then always calculated in advance the respectively temporally subsequent temperature value of the plate at time t ₊ = t + Δt according to the calculation rule T P (t + Δt) = T P (t) - [T P (t) / τ + T T (T) / CR 1 + T H (T) / CR 2 ] At.

Finally, with the temperatures T _T (t), T _P (t) and T _H (t) known therewith, the flow-rate constant is obtained at some point in time t as K (t) = K 0 + K T T T (t) + K P T P (t) + K H T H (T), wherein the constants K ₀ , K _T , K _P , K _{H have} been determined experimentally and during operation of the flowmeter only the temperatures T _T (t) and T _H (t) are measured.

there In addition, it should be noted that the solution presented the "temperature calculation instead of temperature measurement" and subsequent Compensation with respect to the temperature distribution or more spatially distributed temperature values in principle can extend any measuring devices.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• WO 04053428 [0009]

Claims (13)

Vibration-type measuring device for measuring at least one process variable, in particular a mass flow, a density, a viscosity, a pressure or the like, in particular in a process line through which a medium can flow, comprising at least one measuring sensor which delivers a measurement signal that can be influenced by the process variable, wherein the the measured value of the process variable determined from the measuring signal can be determined from a functional context in connection with measuring parameters, and wherein the measuring parameters have a temperature-dependent cross-sensitivity with respect to the temperature distribution in the measuring device, characterized in that the measuring device comprises at least one temperature sensor, via which the local temperature can be measured and subsequently by electronic means ( 3 ) a temperature distribution field can be calculated by means of a temperature distribution theorem, and that correction values for compensating the temperature-dependent cross-sensitivities of the measurement parameters can be determined from the temperature field data. Measuring device according to claim 1, which is a Coriolis flow measuring device with at least one flow measuring tube and an evaluation unit, characterized in that at least one point of the Coriolis flow measuring tube or measuring device, a temperature sensor ( 2 via which the local temperature can be measured and subsequently with electronic means ( 3 ) a temperature distribution field can be calculated from a temperature distribution theorem, which corresponds to the evaluation unit. Measuring device according to claim 1 or 2, characterized in that the temperature field determination unit ( 3 ) is structurally integrated into the evaluation unit. Measuring device according to one of the preceding claims, characterized characterized in that the temperature distribution theorem is the analytical one or numerical solution of the partial differential equations the heat propagation in the meter comprises, wherein the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) a location dependence corresponding to the meter having. Measuring device according to one of the claims 1 to 3, characterized in that the temperature distribution theorem the analytical or numerical solution of ordinary Differential equations that are over a thermal network describe modeled heat propagation in the device, includes. Measuring device according to one of the preceding claims, characterized characterized in that the determination of the current temperature distribution field from the temperature distribution theorem under consideration from past temperature readings and / or past calculated temperature distributions takes place. Method for operating a measuring device vibration type, in particular a Coriolis flowmeter, characterized in that at least one point of the measuring tube or a temperature sensor is placed is measured above the local temperature and then one Temperature distribution field from a temperature distribution theorem is calculated, and that from the temperature field data correction data to compensate for temperature-dependent cross-sensitivities be determined. Method according to claim 7, characterized in that that the temperature distribution theorem the analytical or numerical Solving the partial differential equations of heat propagation in the Measuring device includes, where the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) a location dependence corresponding to the meter having. A method according to claim 8, characterized in that with the following formal relationship, the temperature distribution field by electronic calculation of an analytical or numerical solving the partial differential equations of heat dissipation in the device is determined by the heat to be solved heat equation for the temperature distribution T (x, y, z; ) is based

wherein the volume heat capacity c (x, y, z) and the thermal conductivity k (x, y, z) then has a location dependence corresponding to the device. A method according to claim 9, characterized in that the temperature distribution takes place under the boundary conditions that the following applies T (x ^ 2 + y ^ 2 = r, 0 <z <l) = T M (T), and that the tube of radius r and length l is anywhere on the time-dependent medium temperature. A method according to claim 7, characterized in that the temperature distribution theorem is the analytic or numerical solution of the ordinary differential equations which are the ones over describe thermal network modeled heat propagation in the device includes. Method according to one of claims 7 to 11, characterized in that in addition to the temperature measurement or for temperature field distribution also past temperature readings and / or previous calculated temperature distributions are taken into account become. Method according to one of claims 7 to 12, characterized in that from the temperature field data correction data be determined, from which an amplitude correction takes place, in such a way that only the relevant temperature-corrected amplitude values be used to determine the flow.