Method of determining a density measurement or a measurement of a density dependent measured variable and coriolis mass flow meter executing the method

Abstract

This invention relates to a method for determining the effective density measurement value ρ of a medium using a Coriolis mass flow meter. eff A method (100) for measuring the density-related measured variable, wherein the Coriolis mass flow meter has two oscillators, each having two measuring tubes, which oscillate in pairs relative to each other, are arranged in parallel fluid configurations, and are combined in a manifold at both the inlet and outlet sides, the method comprising the steps of: detecting (110) a first mass flow rate portion measurement of a first portion of the flow through the measuring tube of the first oscillator and a second mass flow rate portion measurement of a second portion of the flow through the measuring tube of the second oscillator, wherein the sum of the two mass flow rate portion measurements gives a total mass flow rate measurement; detecting (120) a first density portion measurement ρ1 and a second density portion measurement ρ2 of the medium in the portion of the flow; and calculating (130) an effective density measurement ρ based on the density portion measurements ρ1 and ρ2, with weights depending on the mass flow rate portion measurements. eff Different weighting functions are used to determine the weights depending on the mass flow rate portion of the measurement.

Description

Technical Field

[0001] This invention relates to a method for determining the measured value of at least one measured variable using a Coriolis mass flow meter, the at least one measured variable being selected from measurements including the effective density of the flowing medium. eff A set of measured variables related to density is considered in a Coriolis mass flow meter having two oscillators, each with two measuring tubes, wherein the measuring tubes of the two oscillators oscillate in pairs against each other, and the four measuring tubes are arranged in parallel flow and grouped together at the inlet and outlet sides in separate manifolds. In this case, the density-related measured variable may particularly include volumetric flow rate. For example, DE 693 14 780 T2 discloses the measurement of volumetric flow rate using a Coriolis mass flow meter with only two measuring tubes connected to form an oscillator, wherein the mass flow rate measurement is divided by the density measurement to obtain the volumetric flow rate value. As long as the measuring transmitter has only one oscillator for determining the mass flow rate and density, the method for determining the volumetric flow rate is clear. However, when there are many parallel flow paths and more than one oscillator, it is necessary to figure out how to weight the different density measurements from the parallel flow paths, especially when large asymmetries between mass flow rates occur together with different densities. Summary of the Invention

[0002] Therefore, the object of the present invention is to provide a method for determining a representative density value, that is, a density-related measured variable—such as volumetric flow rate over the entire flow region—and a Coriolis mass flow meter for performing the method. According to the present invention, this object is achieved by the method as defined herein and the Coriolis mass flow meter as defined herein.

[0003] The method of the present invention is used to determine the measured value of at least one measured variable using a Coriolis mass flow meter, the at least one measured variable being selected from measurements including the effective density of the flowing medium. eff A set of measured variables related to density, the Coriolis mass flow meter has two oscillators, each of which has two measuring tubes, wherein the measuring tubes of the two oscillators oscillate in pairs against each other, wherein the four measuring tubes are arranged in parallel flow and are grouped together on the inlet and outlet sides in separate manifolds, wherein the method includes the following steps: Record the first mass flow rate portion of the first flow rate portion through the measuring tube of the first oscillator. 1 and the second mass flow rate measured by the second flow section of the measuring tube of the second oscillator. 2, where the sum of the two mass flow rate measurements gives the total mass flow rate measurement; Record the measured value of the first density portion of the medium in the first flow section. 1. Measurement of the second density portion of the medium in the second flow section 2; and As measured using a portion of the mass flow rate. 1. 2-weighted two density component measurements 1. A function of 2 to calculate the effective density measurement. eff , Its characteristic is that different weighting functions are applied as functions of the mass flow rate partial measurement value to determine the weighting.

[0004] In a first additional development of the invention, when the total mass flow rate measurement is less than a first limit value, the effective density measurement is calculated using at least a first weighting function of the density portion measurements. eff In this additional development embodiment, the first limit value reaches no more than 4% of the measurement range of the mass flow meter, for example, no more than 3%, and especially no more than 2%, wherein the first limit value according to this embodiment reaches no less than 0.1% of the measurement range, and especially no less than 0.2%.

[0005] In a further development of the invention, the first weighting function includes a first density portion measurement. 1. Measurement values ​​of the second density portion The arithmetic mean of 2. By applying such a weighting function, the density determination is robust to flow fluctuations under low flow conditions.

[0006] In a further development of the invention, when only one mass flow rate component measurement is less than the second limit value, the effective density measurement is calculated using at least a second weighting function of the density component measurements. eff .

[0007] In this additional development of the invention, the second limit value is less than the first limit value, and in particular reaches no more than half of the first limit value.

[0008] In a further development of the invention, the second weighting function weights the density fraction measurements belonging to the larger mass flow rate fraction with x, and weights the smaller of the two density fraction measurements with 1-x, where x > 2 / 3, and especially x > 3 / 4. In this additional development of the invention, x = 1.

[0009] In a further development of the invention, when the total mass flow rate measurement is not less than the first limit value, and when the partial mass flow rate measurements are not less than the second limit value, a third weighting function is used to calculate the effective density measurement. eff In this additional development of the invention, a third weighting function is used to calculate the effective density measurement. eff The third weighting function is equal to the standard density value. standard The standard density value standard It is calculated as follows: .

[0010] In a further development of this invention, the density-related measured variable includes the volumetric flow rate calculated as follows. : , Among them, the total mass flow rate measurement value Includes two mass flow rate measurements 1. The sum of 2.

[0011] The Coriolis mass flow meter of the present invention includes: Measurement and operation circuits; and Two oscillators, each having two measuring tubes, wherein the measuring tubes of the two oscillators oscillate in opposite pairs, wherein the four measuring tubes are arranged in parallel flow and are grouped together on the inlet and outlet sides in separate manifolds, wherein each oscillator has at least two oscillation sensors for recording the oscillations of the measuring tubes and an exciter for exciting the oscillations; The measurement and operation circuitry is adapted to drive the exciter to record the signal from the oscillation sensor and to execute the method of the present invention. Attached Figure Description

[0012] The invention will now be explained in more detail based on examples of embodiments shown in the accompanying drawings, which are as follows: Figure 1 This is a longitudinal cross-sectional schematic diagram of an example embodiment of the Coriolis mass flow meter of the present invention; Figure 2a A flowchart illustrating an example embodiment of the method of the present invention; and Figure 2b yes Figure 2a The following is a detailed flowchart of the method steps of an example embodiment of the method of the present invention. Detailed Implementation

[0013] Figure 1An example embodiment of the Coriolis mass flow meter 1 of the present invention, illustrated, includes a first oscillator 12 having two curved measuring tubes whose centerlines extend in two mutually parallel planes, wherein the orthogonal projection of the centerline of one measuring tube of the first oscillator onto the plane of the centerline of the other measuring tube coincides with the centerline of the other measuring tube. Furthermore, the first oscillator 12 includes a first electric actuator 14 that acts between the two measuring tubes of the first oscillator to drive them to perform curved oscillations. The first electric actuator 14 may be arranged in the longitudinal direction of the measuring tubes, particularly at a point half the length—that is, at the peak of the curve of the measuring tube. Additionally, the first oscillator 12 includes a first inlet-side electric oscillation sensor 16 and a first outlet-side electric oscillation sensor 18, each of which records the movement of the measuring tubes of the first oscillator 12 relative to each other. The Coriolis mass flow meter 1 additionally includes a second oscillator 22 with two curved measuring tubes whose centerlines extend in two mutually parallel planes, wherein the orthogonal projection of the centerline of one measuring tube of the second oscillator onto the plane of the centerline of the other measuring tube coincides with the centerline of the other measuring tube. The second oscillator 22 additionally includes a second electric actuator 24 that acts between the two measuring tubes of the second oscillator to drive them to perform curved oscillations. The second electric actuator 24 can be arranged in the longitudinal direction of the measuring tubes, particularly at a point half the length—that is, at the peak of the curve of the measuring tube. Furthermore, the second oscillator 22 includes a second inlet-side electric oscillation sensor 26 and a second outlet-side electric oscillation sensor 28, each of which records the movement of the measuring tubes of the second oscillator 22 relative to each other. The first oscillator 12 and the second oscillator 22 particularly have two shared planes in which the centerlines of the measuring tubes extend. The four measuring tubes of the two oscillators are arranged in parallel flow, wherein they are grouped together at the inlet side in the first manifold 32 and at the outlet side in the second manifold 34. Manifolds 32 and 34 each have flanges for inserting the Coriolis mass flow meter 1 into the pipe. Manifolds 32 and 34 are connected together by a solid support tube 30 to suppress movement of the manifolds relative to each other. The bends of the measuring tubes extending outside the support tube 30 are covered by a housing cover 36, which connects to the support tube along its peripheral edge to seal the measuring tubes of the two oscillators 12 and 22.The Coriolis mass flow meter 1 additionally includes an electronics housing 40 in which a measurement and operation circuit 44 is arranged. This circuit is connected to inlet sensors 16, 26, outlet sensors 18, 28, and actuators 14, 24 to drive the actuators 14, 24, thereby recording the signals from the oscillation sensors 16, 18, 26, 28, and performing the method of the invention, as will be explained below. The measurement and operation circuit 44 is connected to a control system via line 46, receives power from the control system, and outputs the identified measurement values ​​to the control system.

[0014] Figure 2a and Figure 2b An example of an embodiment of the method 100 of the present invention illustrated in the figure begins with the recording 110 of a first mass flow rate portion of the first flow rate portion through the measuring tube of the first oscillator. 1 and the second mass flow rate measured by the second flow section of the measuring tube of the second oscillator. 2. Each of these values ​​is determined based on the phase difference or time delay between the sensor signal of its oscillator and the oscillator-specific calibration factor.

[0015] The above two mass flow rate measurements 1、 The sum of 2 corresponds to the total measured mass flow rate. ; Next, record the measured value of the first density portion of the medium in the first flow section of 120. 1. Measurement of the second density portion of the medium in the second flow section 2. To this end, for each of the two oscillators, the resonant frequency of at least one bending oscillation mode is determined, so as to determine the density portion of the medium in the measuring tube of the oscillator.

[0016] Then, using measurements that depend on the mass flow rate portion. 1. With a weight of 2, the two density components are measured. 1. Use a function of 2 to calculate the effective density measurement value of 130. eff Different weighting functions are applied as functions of the mass flow rate portion of the measurement to determine the weights. The following uses... Figure 2b Let me explain the details in this regard.

[0017] Then, based on the total mass flow rate measurement and effective density measurement value eff The volumetric flow rate is calculated according to the following formula. (140): .

[0018] The volumetric flow rate determined in this way, along with other determined measurements, can be output to the control system.

[0019] based on Figure 2b We will now explain which weighting functions are used to calculate the effective density measurement and how to choose these weighting functions.

[0020] In the first sub-step (131), the total mass flow rate measurement is checked. Whether the value is less than the first limit value L1. The first limit value L1 can, for example, reach 2% of the measurement range of the Coriolis mass flow meter, that is, 2% of the maximum mass flow rate specified for the device.

[0021] If the result is positive, the effective density measurement is determined in the second sub-step (132) using a first weighting function (G1). The first weighting function (G1) comprises the components that form the first density partial measurement. 1. Measurement values ​​of the second density portion The arithmetic mean of 2, that is, eff = ( 1 + 2) / 2.

[0022] In the case of a negative result, in the second test of the third sub-step (133), it is checked whether there is exactly one of the mass flow rate measurements that is less than the second limit value L2, wherein it is currently preferred that L2 = L1 / 2.

[0023] In the case of a positive result from this second test, the density portion is measured in the fourth sub-step (134). 1. The second weighting function G2 is used to calculate the effective density measurement. eff The second weighting function G2 weights the density measurements belonging to the larger mass flow rate portion with x, and weights the smaller of the two density measurements with 1-x, where x > 2 / 3, and especially x > 3 / 4. In this case, x can especially take the value of 1. With this choice of parameter x, the effective density measurement... eff It is equal to the density portion of the measurement that belongs to the larger mass flow rate portion.

[0024] In the event of a negative result from the second test, the effective density measurement is calculated in the fifth sub-step (135) using the third weighting function G3. eff The effective density measurement was calculated using the third weighting function. eff Equal to standard density value standard The standard density value standard It is calculated as follows: .

[0025] Effective density measurement eff It can be calculated using the formula above for standard density values; however, the effective density measurement value... eff It can also be calculated using other equivalent formulas that yield the same result.

Claims

1. A method (100) for determining a measured value of at least one measured variable using a Coriolis mass flow meter, said at least one measured variable being selected from measurements including the effective density of a flowing medium. eff A set of measured variables related to density, the Coriolis mass flow meter has two oscillators, each of which has two measuring tubes, wherein, The measuring tubes of the two oscillators oscillate in opposite pairs, wherein the four measuring tubes are arranged in parallel flow and are grouped together on the inlet and outlet sides of independent manifolds, wherein the method includes the following method steps: Record (110) the first mass flow rate portion of the first flow rate measured through the measuring tube of the first oscillator of the two oscillators. 1 and the second mass flow rate portion of the measuring tube of the second oscillator of the two oscillators. 2, where the sum of the two mass flow rate measurements gives the total mass flow rate measurement; Record (120) the measured value of the first density portion of the medium in the first flow rate portion. 1 and the measured value of the second density portion of the medium in the second flow section. 2; and As measured using a portion of the mass flow rate.

1. 2-weighted two density component measurements 1. The function of 2 is used to calculate the effective density measurement value of (130). eff , The characteristic feature is that different weighting functions are applied as functions of the mass flow rate partial measurement to determine the weighting.

2. The method according to claim 1, wherein, When the total mass flow rate measurement is less than the first limit (L1) (131), the effective density measurement is calculated (132) using at least a first weighting function of the density portion measurement. eff .

3. The method according to claim 2, wherein, The first weighting function (G1) includes the first density portion of the measured value. 1 and the second density portion measurement value The arithmetic mean of 2.

4. The method according to claim 2, wherein, When only one mass flow rate component measurement is less than the second limit value (L2) (133), the density component measurement is used.

1. The effective density measurement (134) is calculated using at least a second weighting function (G2) of 2. eff .

5. The method according to claim 4, wherein, The second limit value (L2) is less than the first limit value (L1).

6. The method according to claim 4, wherein, The second limit value (L2) is no more than half of the first limit value (L1).

7. The method according to any one of claims 4 to 6, wherein, The second weighting function (G2) weights the density fraction measurements belonging to the larger mass flow rate fraction with x, and weights the smaller of the two density fraction measurements with 1-x, where x > 2 / 3.

8. The method according to claim 7, wherein, x > 3 / 4。 9. The method according to claim 7, wherein, x = 1。 10. The method according to any one of claims 4 to 6, wherein, When the total mass flow rate measurement is not less than the first limit value (L1), and when the partial mass flow rate measurements are not less than the second limit value (L2), the effective density measurement is calculated (135) using the third weighting function (G3). eff .

11. The method according to claim 10, wherein, The effective density measurement calculated using the third weighting function (G3) eff Equal to standard density value standard The standard density value standard It is calculated as follows: 。 12. The method according to claim 1, wherein, The density-related measured variable includes the volumetric flow rate calculated according to the following formula (140). : ， Among them, the total mass flow rate measurement value Includes two mass flow rate measurements 1. The sum of 2.

13. A Coriolis mass flow meter (1), comprising: Measurement and operation circuit (44); as well as Two oscillators (12, 22), each having two measuring tubes, wherein the measuring tubes of the two oscillators (12, 22) oscillate in pairs against each other, wherein the four measuring tube flows are arranged in parallel flow and are grouped together at the inlet and outlet sides in independent manifolds (32, 34), wherein each oscillator (12, 22) has at least two oscillation sensors (16, 18, 26, 28) for recording the oscillations of the measuring tubes and an exciter (14, 24) for exciting the oscillations; wherein the measurement and operation circuit (44) is adapted to drive the exciter (14, 24) to record the signals of the oscillation sensors (16, 18, 26, 28) and perform the method according to any one of claims 1 to 12.

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