Ultrasonic, laser or radar: choosing a distance sensor
, 4 min read
Choose ultrasonic for low cost, short range and targets of any colour or transparency; laser for long range, small targets and fast updates; and mmWave radar for tens of metres, speed measurement and rain, fog or dust.
At a glance
| Ultrasonic | Laser ToF | mmWave radar | |
|---|---|---|---|
| Typical range | Centimetres to about 10 m | Centimetres to tens of metres | Tens to hundreds of metres |
| Beam | Wide cone | Narrow spot | Shaped by antenna, wide or narrow |
| Glass and clear liquids | Measures them | Light passes through or scatters | Partly transparent |
| Dark or black targets | No effect | Shorter range | No effect |
| Rain, fog, dust | Mostly works | Degraded | Works |
| Measures speed | No | No | Yes, directly |
| Relative cost | Lowest | Medium | Highest |
When ultrasonic wins
Parking, robot obstacle avoidance, tank and bin levels, and presence detection. A wide beam sees obstacles a narrow beam would miss, and the sensor does not care about colour, transparency or light.
When laser wins
Long range with a small spot, high resolution and fast update rates: positioning, small targets, and places where the beam must not touch nearby walls.
When radar wins
Vehicles moving at speed, outdoor sensing in all weather, and anything where you need the speed of the target as well as its distance, such as blind-spot warning and door-opening protection.