Ultrasonic flowmeter and method for operating an ultrasonic flowmeter

1 . A method for operating an ultrasonic flowmeter, wherein the ultrasonic flowmeter includes at least a first ultrasonic transducer and a second ultrasonic transducer and a control and evaluation unit, wherein the control and evaluation unit is connected to the first ultrasonic transducer and the second ultrasonic transducer, wherein the first ultrasonic transducer and/or the second ultrasonic transducer is/are designed as an ultrasonic transmitter and/or ultrasonic receiver, wherein the first ultrasonic transducer and/or the second ultrasonic transducer is or are designed as a wedge transducer, wherein the first ultrasonic transducer and the second ultrasonic transducer are arranged on a measuring tube in such a way that a signal path is formed between the first and the second ultrasonic transducer, so that a measuring signal emitted by the ultrasonic transmitter runs via the signal path to the ultrasonic receiver, wherein the first ultrasonic transducer has a first array of at least two active elements and/or the second ultrasonic transducer has a second array of at least two active elements, the method comprising:

the control and evaluation unit separately controlling at least two active elements of the array arranged on the first ultrasonic transducer and/or at least two active elements of the array arranged on the second ultrasonic transducer;

the control and evaluation unit controlling the array functioning as an ultrasonic transmitter in such a way that a radiation angle of the measuring signal is varied at least at times, and/or varying a reception characteristic of the array functioning as an ultrasonic receiver at least at times;

in order to determine the flow rate during measurement, the measuring signal impinging on the ultrasonic receiver in an optimized manner and/or the ultrasonic receiver receiving the measuring signal in an optimized manner with respect to the radiation angle;

wherein for installation of the ultrasonic transducers on the measuring tube, the ultrasonic transmitter emits a measuring signal;

wherein by pivoting the reception characteristic of the ultrasonic receiver, the pivoting angle at which the ultrasonic receiver optimally receives the measuring signal, is determined; and

wherein the control and evaluation unit, starting from the pivoting angle and taking into account a geometry of the signal path, determines a position for the ultrasonic transmitter and/or the ultrasonic receiver at which the ultrasonic transmitter array transmits the measuring signal in a non-pivoted manner and at which the ultrasonic receiver array receives the measuring signal in a non-pivoted manner.

2 . The method according to claim 1 , wherein at least the ultrasonic transducer operating as an ultrasonic transmitter in an operating state has an array of at least two active elements, wherein the at least two active elements of the ultrasonic transmitter are separately controllable by the control and evaluation unit;

wherein, in a first operating state, the first active element of the ultrasonic transmitter emits a first ultrasonic signal;

wherein the second active element of the ultrasonic transmitter emits a second ultrasonic signal; and

wherein the first ultrasonic signal and the second ultrasonic signal are superimposed to form the measuring signal.

3 . The method according to claim 2 , wherein the measuring signal has at least one main lobe and at least two side lobes and/or at least two grid grating lobes due to a superposition of at least the first ultrasonic signal and the second ultrasonic signal.

4 . The method according to claim 3 , wherein the first ultrasonic signal and the second ultrasonic signal are emitted at least at times with a time delay and/or with different amplitude and/or with different phase, whereby the radiation angle of the measuring signal of the main lobe of the measuring signal is changed.

5 . The method according to claim 2 , wherein the measuring signal has at least one main lobe and at least two side lobes and/or two grid grating lobes;

wherein at least at times the at least one main lobe or at least one side lobe or at least one grating lobe is aligned with the measuring tube in such a way, that the main lobe or the side lobe or the grating lobe is reflected at the measuring tube and the reflection is received again by the array of active elements initially operating as an ultrasonic transmitter; and

wherein the control and evaluation unit determines from the reflection of the main lobe or the side lobe or the grating lobe at least one item of information about an operating state and/or a measuring environment.

6 . The method according to claim 5 , wherein the at least one main lobe or the at least one side lobe or the at least one grating lobe is aligned at least temporarily with the measuring tube in such a way that the at least one main lobe or the at least one side lobe or the at least one grating lobe excites a Lamb wave which propagates along a measuring tube wall in a direction of the ultrasonic receiver and which is detected by the ultrasonic receiver, wherein the amplitude and/or a propagation time and/or a spectrum of the Lamb wave is evaluated.

7 . The method according to claim 1 , wherein, at least at times, the signals measured at the individual active elements of the array functioning as an ultrasonic receiver are superimposed on one another in a time-delayed and/or phase-shifted manner and/or weighted with different amplitude, whereby the reception characteristic of the ultrasonic receiver is pivoted.

8 . The method according to claim 1 , wherein the control and evaluation unit monitors an amplitude of the measuring signal detected by the ultrasonic receiver, and the radiation angle of the measuring signal and/or the reception characteristic of the ultrasonic receiver is changed if the amplitude falls below a threshold value.

9 . The method according to claim 8 , wherein the control and evaluation unit varies the radiation angle of the measuring signal and/or the reception characteristic of the ultrasonic receiver at regular or irregular intervals in order to maximize the measuring signal at the ultrasonic receiver;

wherein, during the variation, the control and evaluation unit detects a maximum of the amplitude at the ultrasonic receiver as well as the corresponding control parameters of the active elements thereto; and

wherein the control and evaluation unit subsequently controls the array of at least two active elements of the ultrasonic transmitter and/or of the ultrasonic receiver in accordance with the determined control parameters.

10 . The method according to claim 9 , wherein the control and evaluation unit adjusts the radiation angle of the measuring signal emitted by the ultrasonic transmitter and/or the reception characteristic of the ultrasonic receiver depending on a measured flow velocity of the medium and/or depending on a sonic velocity of the medium, in such a way that the measuring signal is maximized at the ultrasonic receiver.

11 . The method according to claim 1 , wherein the control and evaluation unit has a memory unit; and

wherein a relationship between a radiation angle of a measuring signal or control parameters for the array of active elements of the ultrasonic transmitter and/or the ultrasonic receiver and different media and/or different flow rates and/or different sound velocities is stored in the memory unit, so that when the flow rate changes and/or when a medium changes, the control and evaluation unit automatically adjusts the radiation angle of the measuring signal and/or the control parameters for the array of active elements and/or the reception characteristic of the ultrasonic receiver in accordance with the stored relationship.