Ultrasonic Distance Sensing

Ultrasonic method of measuring distance from a solid or liquid.

Ultrasonic distance sensors are contactless measurement devices which transmit and receive high frequency acoustic waves to measure the distance from the surface of a liquid substance or solid object.

Ultrasound distance sensor technology transmits a high frequency sound wave pulse and receives the wave echo reflected off an object. The time taken for the acoustic pulse to traverse the distance between the transmitter and target surface, and back again to the receiver is measured.

The distance (d) between the ultrasonic distance sensor and the target surface can be calculated by dividing the time taken (t) by two, and multiplying that by the speed of sound (c) in air, i.e. d = c ∙ t / 2.

The performance of a ultrasonic distance sensor is mainly affected by changes in the speed of sound and disturbances on the surface of the target or between the sensor and the target object.

The speed of sound will change if the air density changes. Since air density changes in the Earth’s atmosphere are directly related to changes in air temperature (measured in Kelvins), an ultrasonic distance sensor is compensated by incorporating an air temperature sensor.

Since there is no contact with the object to be measured, ultrasound distance measurement technology can be used in applications where sensors requiring contact are otherwise prohibited. These sensors have no moving parts which makes them very reliable, requiring very little maintenance.

Ultrasonic distance sensors are typically housed in a single assembly combining the acoustic transmitter and receiver in one device.

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