Proximity Sensors: A Detailed Explanation


Several proximity sensors find use, especially alongside Arduino in the current industry applications. However, picking the most reliable one for your intended use can be challenging. We’ll explain several types of proximity sensors and give you a few tips on selecting the best one. 

Table of Contents

What are Proximity Sensors?

A proximity sensor is a device that recognizes an object’s availability when the thing enters its field without contact. Thus, depending on the type of sensor, light, sound, electromagnetic fields, infrared, etc., may find use in detecting the target.

How Do Proximity Sensors Work?

First, the proximity sensor radiates electromagnetic radiation such as infrared. Next, it observes if a change in the radiated electromagnetic field will change. The “sensed’ object is also known as the sensor’s target.

Types Of Proximity Sensor

  • Capacitive Proximity Sensors

Capacitive proximity sensors have two parallel plates similar to a common capacitor. Thus, if the target or object alters the system’s capacitance, it triggers the sensor. 

Besides, these sensors are the best for designing non-ferrous materials. Also, they’re perfect for close-range tasks such as level monitoring.

Ultrasonic Proximity Sensors

Ultrasonic proximity sensors use sound, which the target can either absorb or reflect. Due to their versatility, they can find use in detecting a wide range of objects. In addition, they can find service over longer distances compared to their counterparts.

Also, they’re ideal for noticing objects whose surfaces have varying properties. Some examples of their applications include industrial automation systems and continuous level control.

Inductive Proximity Sensors

Inductive proximity sensors consist of a wound iron core. When an object finds its way into the sensor’s range, it alters the coil’s inductance, which activates the sensor. 

For this reason, these sensors are good for ferrous materials, especially at close range. Also, they are greatly used in hazardous areas.

Magnetic Proximity Sensors

These sensors are mostly used to detect whether or not an object is present. They function using a magnetic field. As the name reveals, they only detect ferromagnetic objects.

Typically, they’re high-speed. Therefore, they’re most suitable for measuring super fast rotational velocity.

  • IR Proximity Sensor

IR stands for Infrared. Therefore, IR sensors emit an Infrared beam and use it to detect the presence of an object In its range. These sensors work the same way as ultrasonic sensors. However, instead of using sound, they emit infrared.

In addition, IR proximity sensors have an IR light-emitting diode and a light detector. The light detector detects any reflection. Also, the sensor has a signal processing circuit for analyzing the optical spot on the power spectral density (PSD).

  • RF proximity sensors

RF stands for Radio Frequency. Therefore, RF proximity sensors emit radiofrequency and use it to detect targets. In brief, any object on the way will cause a reflection that experts can analyze to reveal its position.

How To Choose a Suitable Proximity Sensor

When selecting the best proximity sensor, you have to consider its intended work, as shown in the table below:

Sensor CriteriaWhat to look atSuitability
Target requirementsAnalyze the object on which to use the sensor.
For example, we can look at the object’s color, material, and shape.
For the sophisticated target requirements, you should use the IR sensor. 
In contrast, ultrasonic sensors are not good for complex requirements.
EnvironmentAlso, it would help if you double-checked the environmental conditions. 
For example, you can look at moisture, temperature, and cleanliness levels.
You can use the capacitive (best one), ultrasonic or inductive sensor for harsh environmental conditions. 
In contrast, the IR proximity sensor is not good for such environments.
Sensing DistanceLastly, have an accurate measurement of the object’s position. 
Thus, this can be far (several meters) or close (a few centimeters).
For close ranges, you should use a capacitive or inductive proximity sensor. 
However, you should use an IR or ultrasonic proximity sensor for long ranges.

In addition, you should note the electrical system where you want to place your proximity sensor. 

For example, you can use a voltage supply or electrical load (NPN/PNP). Whichever case, ensure it works well with the controls you’re using.


We’ve explained what proximity sensors are, how they work, and factors to consider when selecting one. If you have any questions, you can contact us on our website.