4 Types of Distance Sensors & How to Choose the Right One

Ultrasonic distance measurement sensors emit a high-frequency soundwave and record the time it takes before the soundwave is reflected to the sensor.

Distance is measured by calculating the time it took for the soundwave to return against the speed of sound in ambient conditions. As such, ultrasonic distance sensors are great for low-power applications or applications in dim lighting. However, they have a limited detection range and slow refresh rate, making them inadequate for fast-moving objects.

IR distance sensors measure distance based on triangulated reflected IR light. An IR LED emits a beam which reflects off a target and is picked up by a receiver or other photosensitive element.

IR distance sensors are generally small and can function during both day and night. They’re also able to measure complex geometry. However, IR distance sensors have a limited range and are easily affected by environmental conditions.

Laser distance sensors - also called laser displacement sensors - may work in several different ways. Comon methods include time-of-flight (in which the sensor derives distance from the time it takes light to reflect) and triangulation (in which distance measurements are achieved by analyzing the angle of the reflected laser beam).

Laser distance sensors deliver precise and stable results across different applications and operating environments. They typically have a much longer measurement range. However, they do pose a risk to the eye safety of operating personnel and usually feature a large form factor.

Proximity sensors are commonly associated with distance sensors due to seemingly similar functions; however, it’s important to note that proximity sensors do not actually measure distance. Instead, they simply sense if an object is within their sensing range, not the distance between objects or between an object and the sensor.

Resolution

Resolution refers to the smallest changes in distance that a sensor is capable of detecting. For example, Infrared sensors typically have a resolution of about 5 mm (though there are more precise IR sensors on the market). Laser sensors may have a resolution of about 1 mm. In fact, some laser sensors can detect micron-level changes.

Sampling rate/Refresh rate

This metric is usually measured in Hz/s and comes into play when measuring the distance between moving objects. The higher the number of readings the sensor receives per second, the more precise the distance measurement is when approaching or moving away from an observed object.

Range

In the context of distance sensors, range refers to the maximum distance at which different types of distance measurement sensors can return accurate and reliable readings. For example, LiDAR scanners have detection distances of up to 2000 m with ±2 cm accuracy.

Target material

Reflective, transparent, and absorptive surfaces can significantly affect a sensor’s performance. Make sure to choose a sensor suitable for the type of material you’re measuring the distance from.