Ultrasonic ranging module
Encyclopedia
An Ultrasonic ranging module, also called a range finder, is a small device that sends out an ultrasonic
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

 sound via a transducer
Transducer
A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...

, and since the sound has a very high frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

, a frequency that we can not hear, it bounces off objects pretty easily. Its main job is just to record the time it takes for the sound to bounce back and into the transducer. Then a controller will do the mathematics to determine the distance between the module and an object. there is a down side to some range finders, in robotics, it only can measure up to a few inches....
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