A method of operating an ultrasonic flowmeter, the method comprising:
- providing the ultrasonic flowmeter that comprises:
- at least one pair of ultrasonic transducers comprising a first ultrasonic transducer and a second ultrasonic transducer;
- at least one third ultrasonic transducer;
- at least one ultrasonic transducer holder arrangement and a control and evaluation unit,
- wherein the ultrasonic transducer holder arrangement has at least one ultrasonic transducer holder,
- wherein the ultrasonic transducer holder arrangement is arranged on a measuring tube, the measuring tube having a measuring tube wall,
- wherein a medium is present in the measuring tube such that the medium is adapted to flow through the measuring tube,
- wherein the first and second ultrasonic transducers are arranged on the ultrasonic transducer holder arrangement,
- wherein the first ultrasonic transducer and the second ultrasonic transducer are arranged offset from one another as viewed in a direction of flow of the medium such that they span between them a measuring path that passes through the ultrasonic transducer holder arrangement, the measuring tube wall and the medium so that a measuring signal emitted by the first ultrasonic transducer is received by the second ultrasonic transducer and vice versa, the measuring signal adapted to pass through three materials, namely the ultrasonic transducer holder arrangement, the measuring tube wall and the medium, and
- wherein the third ultrasonic transducer is arranged on the ultrasonic transducer holder arrangement such that it defines at least a first reference path that passes through the ultrasonic transducer holder arrangement, the measuring tube wall and the medium,
- wherein the third ultrasonic transducer is designed and arranged such that it receives and optionally also transmits a reference signal which propagates along the first reference path, and
- wherein the control and evaluation unit is designed to control the ultrasonic transducers and to evaluate the signals received from the ultrasonic transducers;
- emitting the measuring signal by the first ultrasonic transducer or the second ultrasonic transducer, wherein the measuring signal propagates along the measuring path;
- receiving the measuring signal by the second ultrasonic transducer or the first ultrasonic transducer and determining a total transit time ttotal, wherein ttotal corresponds to the total transit time of the measuring signal between the first ultrasonic transducer and the second ultrasonic transducer;
- emitting the reference signal by the third ultrasonic transducer or another ultrasonic transducer;
- receiving the first reference signal by the third ultrasonic transducer and determining the reference transit time tref, wherein tref corresponds to the transit time of the reference signal between the ultrasonic transducer transmitting the reference signal and the third ultrasonic transducer;
- and
- determining a velocity of the flowing medium using known constructive parameters of the measuring arrangement, the measured transit times tref and ttotal and the sound velocity of the ultrasonic transducer holder.