How Do Distance Sensors Work?

Radar

Radar is a form of distance sensor that uses radio waves or microwaves. These waves are directed at objects, which reflect some of the radar signal back to the source. The measurement of the time it takes for a given signal to return to the point of origin can yield a wealth of data, including its distance from that point.

Sonar

Sonar works in a fashion similar to radar, except that it uses sound instead of radio or microwaves. Sonar is typically employed by humans only in underwater conditions, but some land animals (like bats) have a natural form of sonar that they use in the air.

Proximity Sensor

This is a type of sensor that operates by creating a field or a directed beam, and relies upon detecting changes in that field/beam to determine the distance and direction of an intruder. There are a plethora of proximity sensor designs, including radar and sonar proximity sensors. Others are photocell, laser, magnetic and thermal.

Laser Range Finders

Laser range finders also bounce energy off an object to collect information from it, in this case the energy of a laser beam. This technology (like radar and sonar before it) was initially developed for a strictly military application, but recently hand-held civilian laser range finders have come onto the market.