What Is a Proximity Sensor?
A proximity sensor is a sensor that detects an object approaching within a certain distance without contact. It doesn't measure distance; it only gives "present/absent" information.
Types and Operation
| Type | Detects |
|---|---|
| Inductive | Metal objects (magnetic) |
| Capacitive | Any object (capacitance) |
| Optical (IR) | Light reflection |
Inductive Sensor
When metal enters a coil's magnetic field, the inductance changes; the sensor detects this. It's the most common contactless detection method in industry.
Where Is It Used?
The phone turning off the screen when it nears the ear, part counting on a production line, door/security systems and robotics.
Sensing Distance (Sn)
Every proximity sensor has a nominal sensing distance (Sn); it's the range at which it reliably detects an object. In inductive sensors this distance also varies with the target metal type (steel, aluminum, brass); the correction factor in the datasheet is taken into account.
Common Mistakes
- Choosing the wrong type: an inductive sensor detects only metal; for plastic a capacitive/optical one is needed.
- Exceeding the sensing distance: every sensor has a limited range.
- Environmental effects: optical types are affected by dust/light.
Frequently Asked Questions
What's the difference between a proximity and a distance sensor?+
How does a phone's proximity sensor work?+
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