![]() Since piezoelectric materials generate a voltage when force is applied to them, they can also work as ultrasonic detectors. The diagrams show the sound fields of an unfocused and a focusing ultrasonic transducer in water, plainly at differing energy levels. The beam pattern of a transducer can be determined by the active transducer area and shape, the ultrasound wavelength, and the sound velocity of the propagation medium. On the other hand, capacitive transducers use electrostatic fields between a conductive diaphragm and a backing plate. Piezoelectric crystals are able to change their sizes and shapes in response to voltage being applied. The transducers typically use piezoelectric transducers or capacitive transducers to generate or receive ultrasound. Ultrasonic transducers convert alternating current (AC) into ultrasound and vice versa. ![]() Sound pressure field of the same ultrasonic transducer (4 MHz, N = 67 mm) with the transducer surface having a spherical curvature with the curvature radius R = 30 mm The plot shows the sound pressure at a logarithmic db-scale. Transducers Sound field of a non focusing 4 MHz ultrasonic transducer with a near field length of N = 67 mm in water. This enables the measurement resolution to far exceed the wavelength of the sound frequency generated by the transducers. This method can be very precise in terms of temporal and spatial resolution because the time-of-flight measurement can be derived from tracking the same incident (received) waveform either by reference level or zero crossing. This technique is known as Sonomicrometry where the transit-time of the ultrasound signal is measured electronically (ie digitally) and converted mathematically to the distance between transducers assuming the speed of sound of the medium between the transducers is known. Ultrasound can also be used to make point-to-point distance measurements by transmitting and receiving discrete bursts of ultrasound between transducers. This technology, as well, can detect approaching objects and track their positions. Systems typically use a transducer that generates sound waves in the ultrasonic range, above 18 kHz, by turning electrical energy into sound, then upon receiving the echo turn the sound waves into electrical energy which can be measured and displayed. Further applications include: humidifiers, sonar, medical ultrasonography, burglar alarms and non-destructive testing. To measure tank or channel liquid level, and also sea level ( tide gauge), the sensor measures the distance ( ranging) to the surface of the fluid. For measuring speed or direction, a device uses multiple detectors and calculates the speed from the relative distances to particulates in the air or water. Ultrasound can be used for measuring wind speed and direction ( anemometer), tank or channel fluid level, and speed through air or water. ![]() Transmitters convert electrical signals into ultrasound, receivers convert ultrasound into electrical signals, and transceivers can both transmit and receive ultrasound. ![]() They can be divided into three broad categories: transmitters, receivers and transceivers. Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. Acoustic sensor A linear array ultrasonic transducer for use in medical ultrasonography Inside construction of a Philips C5-2 128 element curved array ultrasound sensor.
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