There are five main types of proximity [sensors](https://www.ampheo.com/c/sensors), each based on different physical principles and suitable for various applications. Here's a breakdown:

**1. Inductive Proximity Sensor**
* Detects: Metal objects only
* How it works: Uses an electromagnetic field to detect eddy currents induced in metal targets
* Range: Short (typically < 10 mm)
* Advantages: Fast, reliable, resistant to dirt and moisture
* Common use: Industrial automation, CNC machines

**2. Capacitive Proximity Sensor**
* Detects: Both metal and non-metal (plastics, liquids, wood, etc.)
* How it works: Senses changes in capacitance when a target enters the electric field
* Range: Short to medium (a few mm to ~25 mm)
* Advantages: Versatile material detection
* Common use: Level sensing (e.g., for liquids or powders), presence detection

**3. Optical (Photoelectric) Proximity Sensor**
Detects: Any object that reflects or interrupts a light beam
How it works: Uses an IR LED and photodetector; detects object by reflection or beam interruption
Types:

* Reflective (diffuse)
* Retroreflective
* Through-beam

Range: Medium to long (up to several meters)
Common use: Object counting, packaging lines, automation

**4. Ultrasonic Proximity Sensor**
* Detects: Most objects (solid or liquid)
* How it works: Emits ultrasonic waves and measures the time of flight of the reflected signal
* Range: Medium to long (up to several meters)
* Advantages: Works in low visibility, detects transparent and reflective objects
* Common use: Distance measurement, obstacle detection in robotics, parking sensors

**5. Magnetic Proximity [Sensor](https://www.ampheoelec.de/c/sensors) (Reed or Hall Effect)**
Detects: Magnetic fields (typically from a magnet)

How it works:

* Reed switch: Opens/closes in response to a nearby magnet
* Hall effect sensor: Measures magnetic field strength

Range: Short (a few mm to cm)

Common use: Door position detection, speed sensing, robotics

📘 Summary Table