What Are Proximity Sensors?
Proximity sensors are electronic devices that detect the distance of an object in relation to the sensor itself. These devices use electromagnetic radiation to detect how far or near an object is, and then they send out a signal. Proximity sensors are great because they are reliable and have a good life span; they require little to no protective maintenance.
Proximity Sensor Applications
Proximity sensors are usually used in the following applications:
- Mobile devices
- Alarm systems
- Automated industrial processes
Different Types of Proximity Sensors
There are two major types of proximity sensors: Inductive and Capacitive.
Inductive Proximity Sensors
Inductive sensors detect the distance of ferrous and non-ferrous metal objects. These devices use an induction loop as an electromagnetic detection system. When metal is detected, the current flowing in the induction loop increases and a signal is sent to another device when a metal object is detected.
Inductive proximity sensors comprise the following components:
- Oscillator: Changes direct current (DC) to alternating current (AC).
- Wire–wrapped coil: Creates the magnetic field.
- Sensing circuit: Detects the magnetic field and the changes thereof.
- Output processor: Sends a signal to other objects.
Inductive proximity sensors are usually used in traffic lights and metal detectors.
Capacitive Proximity Sensors
Capacitive proximity sensors detect nearby metal and non-metal objects, without physical contact. They are similar to inductive sensors in shape and size but differ in that they are mostly used for non-metallic objects.
Capacitive proximity sensors emit an electrostatic field to detect the change in the capacitance caused by an object that enters the field.
These proximity sensors comprise the following components:
- A capacitive probe or plate
- An oscillator
- A signal level detector
- A solid-state output switching device
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