Ultrasonic Transducer

Ultrasonic Sensor

An ultrasonic transducer is a device that converts energy into ultrasound, or sound waves above the normal range of human hearing.

Systems typically use a transducer which generates sound waves in the ultrasonic range, above 18,000 hertz, by turning electrical energy into sound, then upon receiving the echo turn the sound waves into electrical energy which can be measured and displayed.

Ultrasonic sensors (also known as transceivers when they both send and receive) work on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor. Sensors calculate the time interval between sending the signal and receiving the echo to determine the distance to an object.

Construction of Ultrasonic Sensor

Piezoelectric crystals are used for this conversion process. Piezoelectric crystals will oscillate at high frequencies when electric energy is applied to it. The reverse is also true. These piezoelectric crystals will generate electrical signals on receipt of ultrasound. These sensors are capable of sending ultrasound to an object and receive the echo developed by the object. The echo is converted into electrical energy for onward processing by the control circuit.

Interfacing & Features

  • description: ultrasonic transducer – receiver
  • input voltage: 20Vrms
  • operating temperature: -20°C to +85°C
  • range: 0.2 to 6m
  • nominal frequency: 40kHz
  • sensitivity: -67dB min.
  • sound pressure: 112dB min.

General Functional Block Diagram

Block diagram of ultrasonic sensor

This technology can be used for measuring: wind speed and direction ,fullness of a tank and speed through air or water. 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. To measure the amount of liquid in a tank, the sensor measures the distance to the surface of the fluid.


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