Proximity Sensor Types

Proximity Sensor Types


Are you curious about proximity sensors? If the answer is Yes! then this blog has got you covered! we explore the different types of proximity sensors, such as inductive, capacitive, and ultrasonic sensors, and their uses in various industries. Additionally, we provide a comparison table to help readers understand the differences between each sensor type. Whether you're an engineer or just interested in the technology behind these sensors, this blog is a must-read!


Proximity sensors are an important part of automation and robotics. They detect objects or signals without any contact between them, which eliminates the need for physical contact with a machine or object being sensed. Proximity sensors come in various shapes and sizes, depending on their application. Common types of proximity sensors include infrared (IR) proximity sensors, ultrasonic proximity detectors as well as capacitive field effect transistors (C-FETs).

IR sensing is predominantly employed to measure distances whereas ultra sonic devices function more effectively when used over large areas due noncontact mode of operation achieved by sending out sound waves that bounce off nearby surfaces enabling detection of near distance objects accurately at long ranges even through obstacles like walls and water droplets among other things . C-FET based solutions offer higher sensitivity compared to optics driven techniques while displaying better performance characteristics such light immunity under low cost making it apt for demanding industrial applications where accuracy is paramount requirement along with reliability,

What is a Proximity Sensor?

The proximity sensor is a device used to detect nearby objects. When the object comes into its sensing area an electrical signal gets generated and this helps to detect the object.

Read our blog about how does a proximity sensor work where we discuss what are proximity sensors, features of proximity sensors, how does proximity sensor work, and the different types of proximity sensors.

Types of Proximity Sensor and their Uses

Proximity sensors are used in many applications to detect objects without physical contact. They can measure distance, presence, speed and direction of an object relative to the sensor itself. There are different proximity sensor types such as ultrasonic ones which emit high-frequency sound waves that bounce off a target surface; capacitive ones with two conductive plates forming a capacitor; inductive magnetostrictive using magnetic fields generated by current flow through coil windings or permanent magnets; photoelectric devices relying on principles involving light sources like infrared beams which activate output when penetrated by an obstacle and active optical systems utilizing laser technology for sensing objects within its line-of-sight range. For precise application requirements you must select the right type based upon your needs so be sure to study each one thoroughly!

Based on the non-contact object detection method, there are five proximity sensor types. such as,

  • Capacitive Proximity Sensor.
  • Inductive Proximity Sensor.
  • Magnetic Proximity Sensor.
  • Optical Proximity Sensor.
  • Ultrasonic proximity Sensor.

Let's, discuss these five proximity sensor types and working principle.

Read our blog proximity sensor working principle where we explained the working principle of different types of proximity sensors.

1. Capacitive Proximity Sensor

Capacitive proximity sensor

capacitive proximity sensor types works on the principle of varying capacitance. So, as the capacitance changes corresponding output signal generated also changes. This capacitance change is marked by the shape of the object and the distance of the object from the sensor.



Capacitive proximity sensor construction


The sensor consists of an oscillator, trigger circuit, and output switching device. As the target enters the electric field generated by the sensor, the electric field generated gets obstructed by the target resulting in a change in capacitance which results in a change in amplitude of the oscillator circuit. When the target moves further from the sensor the amplitude of oscillation decreases and when the target comes close amplitude increases. This change triggers the trigger circuit resulting in a change in the output of the sensor and thus glowing the output sensor led.



As shown in the above image they can be used to detect objects on the conveyor belt.

2. Inductive Proximity Sensor

Inductive Proximity Sensor types works on two principles

Faraday's Law of induction

When an electrical conductor is placed in a magnetic field, eddy currents are produced in the conductor.

Lenz’s Law

Lenz’s Law

These eddy currents generate a magnetic field that opposes the cause or the magnetic field which generated it.
This type of sensor has a wire wound around typically an iron core. As shown in the above figure, an alternating current is applied to the coil which generates a magnetic field around it. This magnetic field gives rise to an eddy current in the electrical conductor. These eddy currents then generate an eddy current magnetic field that opposes the electromagnetic field from the sensor. When the target is taken close to the sensor the electromagnetic field from the sensor gets reduced, which decreases the amplitude of the electromagnetic field. When it decreases beyond the threshold trigger circuit activates the output. This helps to identify that object has come into the desired vicinity of the sensor.
Note: It has a similar internal circuit as that of the capacitor sensor.


Inductive proximity sensor

Refer to this guide for interfacing proximity sensor with Arduino to get a hands-on experience with this sensor.

3. Magnetic Proximity Sensor


Magnetic Proximity sensor


This types of proximity sensor works on the principle of the Hall effect. As shown in the figure, a potential voltage is applied across a hall element such as a hall element made of tin. So positive and negative charges start flowing. Now, when a magnet is brought in the vicinity of the hall element material, negative and positive charges get

accumulated across the opposite ends of the plate. When we measure the voltage across it a tiny voltage in microvolts is obtained. This is usually amplified by an amplifier. When the object is taken closer a higher potential gets generated across the plates and when it exceeds the threshold output is set to high. There are various other technologies too used in magnetic proximity sensors such as variable reluctance, reed switches, GMR (Giant Magneto-Resistive effect) inductive

4. Optical Proximity Sensor


Optical Proximity sensor


Optical proximity sensor types consists of a transmitter and a receiver. The transmitter circuit consists of a photo transmitter that sends light out by converting electrical energy into light. This light gets bounced back from the target which is received by the photo receiver. There are three types of optical proximity sensors: through-beam sensor, retro-reflective sensor, and diffuser sensor.

5. Ultrasonic Proximity Sensor


Ultrasonic Proximity Sensor


An ultrasonic proximity sensor consists of a transmitter and receiver. As shown transmitter sends out a sound wave and the receiver detects the reflected wave from the object. You can refer to this guide Arduino Interfacing with an ultrasonic sensor if you want to try something hands-on.

Comparison Table of Proximity Sensors


Capacitive Proximity Sensor

Inductive Proximity Sensor

Magnetic Proximity Sensor

Optical Proximity Sensor

Ultrasonic Proximity Sensor
Sensing distance (mm) 1-35mm (some sensors up to 70mm) Up to 60 mm Up to 80 mm 2-30mm Up to 1000mm

Vibration tolerant

Excellent Excellent Excellent Excellent Poor
Sensitivity Very sensitive to changes in environmental conditions such as temperature and humidity. Adaptable to harsh environments Susceptible to magnetic interference Sensitive to dust and lubricants Temperature variations( since the speed of sound is dependent on temperature
Sensing object material The object can be made up of any material Ferrous metals such as iron and steel.
Non-ferrous metals sensing range decreases(will be given in datasheet)
The object should be of Magnetic material only. The object can be made up of any material. ( fails for a transparent object ) The object can be made up of any material. ( works for transparent objects)
Cost Medium Low Low Medium High
Size small small small small small
Application They are used for detecting parts in conveyors, workstations, and robots. Foil seal detection inside plastic caps, to count metal cans. Used to detect the open or closed status of windows, gates, and doors.
Used in the food industry.
Automatic soap dispenser, optical heart rate monitor, optical liquid level indicator. Liquid level control, robotic sensing, counting people, automobile self-parking technology, and anti-collision safety systems.


In this blog post, we have learned that proximity sensors are vital components in various industries, from automotive to manufacturing. They are designed to detect the presence or absence of objects, making them indispensable for automation and control applications. With different types of proximity sensors available, each with its unique features and uses, it's essential to choose the right one for your specific application. We hope that our comparison table of proximity sensors and detailed explanation of their types and uses has provided valuable insights and helped you make an informed decision. Whether you're looking to improve efficiency, reduce downtime, or enhance safety, proximity sensors can make a significant difference in your operations. So, choose wisely and enjoy the benefits of proximity sensors today!


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Please do check out other blog posts about Popular electronics


Check out other related blog post about sensors : Types of Sensors in IoT , Interfacing Proximity Sensors with Arduino and How proximity sensor works


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Frequently Asked Questions

1. What are the main types of proximity sensors?

The main types of proximity sensors are inductive, capacitive, ultrasonic, and photoelectric sensors.

  • Inductive sensors detect metallic objects by generating an electromagnetic field and measuring changes in the field when a metallic object is brought near.
  • Capacitive sensors detect the presence of any object with a dielectric constant different from the surrounding air by measuring changes in capacitance.
  • Ultrasonic sensors use sound waves to detect the presence of objects by emitting high-frequency sound waves and measuring the time taken for the sound waves to reflect back.
  • Photoelectric sensors use light to detect objects and come in two main types: through-beam sensors, which use a transmitter and a receiver to detect objects passing through the beam, and reflective sensors, which use a single device to emit and detect the reflection of light from an object.

2. What is the best type of proximity sensor?

When contemplating the most fitting proximity sensor to use, there is no sole option that reigns supreme. Every sort of proximity sensor possesses its own advantages and drawbacks contingent on the designated usage. For instance, inductive sensors demonstrate their superiority in pinpointing metallic objects, while capacitive sensors exhibit the ability to detect an extensive array of materials. Ultrasonic sensors have the propensity to discern objects even in soiled or unforgiving atmospheres, whereas photoelectric sensors thrive at identifying lucid or lustrous objects.

It's crucial to take into account the distinct prerequisites of the application when making a decision on the type of proximity sensor. These necessities may include the sort of material that needs to be detected, the range of detection needed, the environment in which the sensor will be utilized, and the desired degree of accuracy. Hence, one must meticulously weigh the specific requirements of the application before opting for the type of proximity sensor that would be most suitable.

3. What are the 4 types of proximity sensors?

  • Ultrasonic Sensors: They measure the distance between two objects using sound waves. These sensors are used in motion control systems, robotic applications and automatic door openers. 
  • Photoelectric Proximity Sensors: This type of proximity sensor uses light beams to detect an object's presence or movement based on its reflection from the optical axis point back into a receiver photodiode which then produces an electrical signal that can be interpreted by microcontrollers or other digital circuit boards for further action/use.
  • Inductive Proximity Sensor: This kind of device works via electromagnetic induction where it transmits high-frequency signals through a coil surrounding the sensing area to generate electrostatic fields around it thereby detecting any metal targets within range without contact required while providing protection against dirt and dust build-up at same time.
  • Capacitive Proximity Sensor: This utilizes electric field variations created when changes occur in capacitance due to being near certain detectable materials like paper, liquids & wood allowing detection levels adjusted as per environment requirements for various industry types.

4. How do proximity sensors work?

Proximity sensors are highly sensitive devices that detect the presence of objects or people. They feature an emitter and a receiver that send out electromagnetic radiation, usually in the form of infrared light beams. When an object is detected by this beam, it bounces back to the receiver which triggers a signal alerting you of its distance and location from one another. This technology has been used widely across many industries such as robotics manufacturing for automated tracking movements, and security systems to protect valuable items or areas monitored with surveillance cameras etc., Proximity sensors can be adjustable allowing precise levels on how far away something should be before sending off a notification ensuring accuracy and performance every time!

5. Can proximity sensor detect distance?

Proximity sensors detect the presence of an object without any physical contact. This non-contact, or remote sensing ability makes these devices suitable for many useful applications. These proximity sensors are also used to measure distance and determine objects' relative position with respect to each other in a given space. The technology behind these cutting-edge IoT devices is extremely sensitive; they can accurately sense distances ranging from millimetres up to several feet away depending on their capabilities - all while being incredibly energy efficient. Thanks to this innovative tech, companies across multiple industries have been able to utilize them in strategic ways that help automate tasks as well as ensure safety protocols are met on a consistent basis ‚Äď proving once again why advanced technologies pave the way forward into smarter living solutions today!

6. How to connect ultrasonic sensor to Raspberry Pi 3?

Connecting an ultrasonic sensor to a raspberry pi 3 b+ is relatively straightforward. The first step in this process is to install the appropriate software on your raspberry pi 3 b+, such as Python and PIP. Once these have been installed you will need to use GPIO pins for connecting the sensor; be sure that they are correctly wired up before continuing with any further steps. To ensure successful communication between the two devices, make certain that input voltage meets or exceeds 5V (the recommended range being between 6-12V). After doing so, connect all four wires from your raspberry pi 3 b+ GPIO header into their respective connection points found underneath of the Sensors PCB board - typically colored red (+5v), black(GND), white (trig) and yellow/blue (echo). Following correct wiring setup then requires writing code which enables connections while providing adequate data exchange functionality through either digital output or analog signals depending upon preference & purpose desired outcome needs match intended goals accurately & reliably . When done right Ultrasonic Sensor integration should seamlessly integrate & become part of complete project without additional upgrades needed based off test results taken during programming phase completed earlier prior hardware installation portion finished properly afterward finally connected until working fine afterwards able accomplish end mission objectives successfully!

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