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CN-121994320-A - Method for operating an ultrasonic flow meter and ultrasonic flow meter

CN121994320ACN 121994320 ACN121994320 ACN 121994320ACN-121994320-A

Abstract

A method for operating an ultrasonic flowmeter is shown and described for measuring a flow through a measuring tube through which a medium flows, wherein the ultrasonic flowmeter comprises at least one transmitting ultrasonic transducer for transmitting an ultrasonic signal and at least one receiving ultrasonic transducer for receiving an ultrasonic signal, and a control and evaluation unit, wherein the control and evaluation unit actuates the transmitting ultrasonic transducer such that it transmits an ultrasonic signal, the receiving ultrasonic transducer receives the transmitted ultrasonic signal, and the control and evaluation unit acquires at least one indirect value for the flow of the medium through the measuring tube by evaluating the transmitted and received ultrasonic signals. The measurement quality is maintained by the control and evaluation unit being adapted to the ultrasonic signal frequency of the emitted ultrasonic signal in such a way that a change in the opening angle of the acoustic cone of the ultrasonic signal, which is caused by a change in the value of the sound speed of the medium, is at least partially compensated for.

Inventors

  • W. Sipper
  • E. Van Dijk

Assignees

  • 克洛纳有限公司

Dates

Publication Date
20260508
Application Date
20251104
Priority Date
20241106

Claims (10)

  1. 1. A method (1) for operating an ultrasonic flowmeter (2) for measuring a flow through a measuring tube (4) through which a medium (3) flows, wherein the ultrasonic flowmeter (2) comprises at least one transmitting ultrasonic transducer (5) for transmitting an ultrasonic signal (6) and at least one receiving ultrasonic transducer (7) for receiving an ultrasonic signal (6) and a control and evaluation unit (8), wherein the ultrasonic transducers (5, 7) are arranged in such a way that they implement an ultrasonic measuring path (9) in the medium (3), and wherein the control and evaluation unit (8) controls the transmitting ultrasonic transducer (5) in such a way that the transmitting ultrasonic transducer transmits the ultrasonic signal (6), the receiving ultrasonic transducer (7) receives the transmitted ultrasonic signal (6), and the control and evaluation unit (8) acquires at least one indirect value for the flow of the medium (3) through the measuring tube (4) by evaluating the transmitted and received ultrasonic signal (6), It is characterized in that the method comprises the steps of, The control and evaluation unit (8) controls the transmitting ultrasonic transducer (5) in such a way that the transmitted ultrasonic signal (6) is transmitted at a defined ultrasonic signal frequency (f_det) such that the ultrasonic signal (6) is transmitted at a defined opening angle (phi_det) of an acoustic cone (10) of the ultrasonic signal (6) with a defined value (v_sos, det) of the sound speed (v_sos) of the medium (3) flowing in the measuring tube (4), The control and evaluation unit (8) obtains a current value (v_sos, akt) for the speed of sound of the medium (3) flowing in the measuring tube (4), the control and evaluation unit (8) changing the ultrasonic signal frequency (f) of the emitted ultrasonic signal (6) to the current value (f_akt) of the ultrasonic signal frequency (f) when the obtained current value (v_sos, akt) of the speed of sound (v_sos) changes relative to a defined value (v_sos, det) of the speed of sound of the medium (3), thereby compensating at least in part for a change in the angle of field (phi) of the sonic cone (10) of the ultrasonic signal (6) due to a change in the value of the speed of sound (v_sos) of the medium (3).
  2. 2. Method (1) according to claim 1, characterized in that the ultrasonic signal frequency (f) of the transmitted ultrasonic signal (6) is varied such that the angle of opening (phi) of the sonic cone (10) of the transmitted ultrasonic signal (6) remains within a tolerance range (delta_phi) around the nominal angle of opening (phi_nom).
  3. 3. Method (1) according to claim 1 or 2, characterized in that the ultrasonic signal frequency (f) is changed in a frequency-hopping manner to the changed current value (f_akt) of the ultrasonic signal frequency, in particular wherein the changed value (f_akt) by being changed to the ultrasonic signal frequency hops from one tolerance limit (phi_tol1) of the tolerance range (delta_phi) to another tolerance limit (phi_tol2) of the tolerance range (delta_phi).
  4. 4. Method (1) according to claim 1 or 2, characterized in that the ultrasonic signal frequency (f) is continuously changed to the changed current value (f_akt) of the ultrasonic signal frequency (f).
  5. 5. Method (1) according to any one of claims 1 to 4, characterized in that the ultrasound signal frequency (f) of the emitted ultrasound signal (6) is changed only when the change in the obtained sound speed (f_akt) with respect to the defined sound speed (f_det) of the medium (3) exceeds a predefined change threshold.
  6. 6. The method (1) according to any one of claims 1 to 5, characterized in that the current value (v_sos, akt) for the speed of sound (v_sos) of the medium (3) flowing in the measuring tube (4) is calculated by the control and evaluation unit (8) itself based on a transmission time measurement of the emitted ultrasonic signal (6) and a known transmission length of the emitted ultrasonic signal (6).
  7. 7. The method (1) according to any one of claims 1 to 5, characterized in that a current value (v_sos, akt) for the speed of sound (v_sos) of the medium (3) flowing in the measuring tube (4) is predefined, in particular by an external parameter input.
  8. 8. Method (1) according to any one of claims 1 to 5, characterized in that a required change of the value of the ultrasonic signal frequency (f) to the current value (f_akt) of the ultrasonic signal frequency (f) is calculated based on a physical mathematical model of wave propagation, in particular by using an equation for describing the dependence of sound pressure (p) on polar angle (phi) with respect to the main emission direction (phi_0) of the transmitting ultrasonic transducer (5), for compensating the effect of the change of sound speed (v_sos) in the medium (3) on the opening angle (phi) of the sonic cone (10) of the ultrasonic signal (6).
  9. 9. An ultrasonic flow meter (2) for measuring a flow through a measuring tube (4) through which a medium (3) flows, having at least one transmitting ultrasonic transducer (5) for transmitting an ultrasonic signal (6) and a receiving ultrasonic transducer (7) for receiving an ultrasonic signal (6), wherein the ultrasonic transducers (5, 7) are arranged such that they implement an ultrasonic measuring path (9) in the medium (3), and wherein the control and evaluation unit (8) actuates the transmitting ultrasonic transducer (5) such that it transmits an ultrasonic signal (6), the receiving ultrasonic transducer (7) receives the transmitted ultrasonic signal (6), and the control and evaluation unit (8) obtains at least one indirect value for the flow of the medium (3) through the measuring tube (4) by evaluating the transmitted ultrasonic signal (6) and the received ultrasonic signal (6), It is characterized in that the method comprises the steps of, The control and evaluation unit (8) controls the transmitting ultrasonic transducer (5) during operation of the ultrasonic flowmeter (2) in such a way that the transmitted ultrasonic signal (6) is transmitted at a defined ultrasonic signal frequency (f_det) such that the ultrasonic signal (6) is transmitted at a defined opening angle (phi_det) of an acoustic cone (10) of the ultrasonic signal (6) with a defined value (v_sos, det) of the sound speed (v_sos) of the medium (3) flowing in the measuring tube (4), The control and evaluation unit (8) obtains a current value (v_sos, akt) for the speed of sound (v_sos) of the medium (3) flowing in the measuring tube (4), the control and evaluation unit (8) changing the ultrasonic signal frequency (f) of the emitted ultrasonic signal (6) to a current value (f_akt) of the ultrasonic signal frequency (f) when the obtained current value (v_sos, akt) of the speed of sound (v_sos) changes relative to a defined value (v_sos, det) of the speed of sound (v_sos) of the medium (3), thereby compensating at least in part for a change in the opening angle (phi) of the cone of sound (10) of the ultrasonic signal (6) due to a change in the value of the speed of sound (v_sos) of the medium (3).
  10. 10. The ultrasonic flow meter (2) according to claim 9, characterized in that the control and evaluation unit (8) implements the method (1) according to the characterizing part of at least one of claims 2 to 8 in operation of the ultrasonic flow meter (2).

Description

Method for operating an ultrasonic flow meter and ultrasonic flow meter Technical Field The invention relates to a method for operating an ultrasonic flowmeter for measuring a flow through a measuring tube through which a medium flows, wherein the ultrasonic flowmeter comprises at least one transmitting ultrasonic transducer for transmitting an ultrasonic signal and at least one receiving ultrasonic transducer for receiving an ultrasonic signal, and a control and evaluation unit, wherein the ultrasonic transducer is arranged in such a way that it implements an ultrasonic measuring path in the medium, and wherein the control and evaluation unit actuates the transmitting ultrasonic transducer in such a way that it transmits an ultrasonic signal, receives an ultrasonic signal, and the control and evaluation unit acquires at least one indirect value for the flow of the medium through the measuring tube by evaluating the transmitted ultrasonic signal and the received ultrasonic signal. The invention also relates to such an ultrasonic flowmeter. Background Flow measurements with ultrasound have been known for decades. Regardless of the particular measurement method used (e.g., transit time measurement, transit time difference measurement (both in and against the flow direction), frequency measurement/Doppler effect), the flow measurement is always based on the follow-up (Mitnahme) of the ultrasonic waves in the medium flowing through the measuring tube, the flow velocity of which medium should be detected. In most ultrasonic flow meters, the characteristic dimension of the measuring tube (measuring tube diameter for a common round measuring tube) is significantly larger than the wavelength of the ultrasonic signal used for the measurement, so that the ultrasonic wave propagating in the medium is understood as a free space wave. It is known to influence the shape of the emitted ultrasonic signal by various measures, for example by a specific design of the geometry of the ultrasonic transducer. In this connection, the opening angle of the ultrasound cone of the emitted ultrasound signal is often mentioned. When there is a maximum sound pressure in the main emission direction of the transmitting ultrasonic transducer, it is acquired at what angle is deviated from the main emission direction, for example, only half the sound pressure is still present. The angle is then regarded as the opening angle of the sound cone, although the sound pressure can of course also be determined if the opening angle exceeds this angle. In any case, the opening angle of the cone of the ultrasound signal is a suitable measure for the degree of focus of the ultrasound signal. A small opening angle of the cone of the ultrasound signal is advantageous in achieving a good signal-to-noise ratio. In an ultrasonic flowmeter having a plurality of measuring paths implemented with a plurality of ultrasonic transducer pairs, the use of a small opening angle of the sonic cone of the ultrasonic signal can avoid or at least reduce the mutual interference of the ultrasonic transducers. If there are installation situations in which the insert (other sensors, stirring devices, etc.) protrudes into the measuring space traversed by the measuring path, disturbing reflections are likewise avoided or reduced by the small opening angle. On the other hand, the acoustic cone must have a sufficiently large opening angle so that the ultrasound signal also reliably covers a sufficiently large reception range. Disclosure of Invention The object of the present invention is to improve a method for operating an ultrasonic flowmeter and a corresponding ultrasonic flowmeter in such a way that the measurement quality remains unchanged even in the case of severely changing measurements. The object of the method for operating an ultrasonic flow meter described at the outset is achieved firstly in that the control and evaluation unit actuates the emitted ultrasonic transducer in such a way that the emitted ultrasonic signal is emitted at a defined ultrasonic signal frequency, so that the ultrasonic signal is emitted at a defined opening angle of the sonic cone of the ultrasonic signal with a defined value of the sound speed of the medium flowing in the measuring tube. These defined conditions and settings of an ultrasonic flowmeter generally correspond to conditions and data according to which the specifications of the ultrasonic flowmeter are based in the case of a specific medium, such as water. In many processes in which ultrasonic flow meters are used, there are less varying process conditions. The invention is based on the observation that in combination with a gaseous medium, the composition of the gaseous medium is subject to a change, which can have a significant influence on the ultrasound signal, in particular on the opening angle of the cone of the emitted ultrasound signal and thus on the measurement. In the case of light gases (e.g. hydrogen), significant differ