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Inductive Proximity Sensor, How it Works & Application

Inductive proximity sensor
Inductive proximity sensor

The inductive proximity sensor is one of the most used types of contactless sensors today, with applications in many industrial systems, consumer electronics, and. Here is an in-depth explanation of the inductive proximity sensor, how it works and its components, among other things such as its application.

What is an Inductive Proximity Sensor?

Just as its name implies, the inductive proximity sensor is a type of non-contact sensing device that uses an electromagnetic field to detect metal targets within its range.

The typical inductive proximity sensor circuit consists of three main components: an internal coil, a soft iron core and an oscillator. The internal coil is wound around the ferrite core and connected to the oscillator circuit.

Inductive sensors come in a variety of shapes, sizes and sensitivities to detect a range of metal targets. The distance at which the sensors can detect objects is dependent on the size and shape of the target object as well as its material composition.

Inductive proximity sensor circuit diagram
Inductive proximity sensor circuit diagram

How do Inductive Proximity Sensors Work?

As earlier mentioned, the proximity sensor working is based on the principles of electromagnetism and electromagnetic induction. In that regard, these sensors can be different types. Most sensors of this type make use of eddy currents to detect objects. The working of inductive proximity sensor is explained below.

Inductive Proximity Sensor Working Principle

When the inductive proximity sensor circuit is activated, it creates a small electromagnetic field in its vicinity, using the oscillator circuit and coil. When a metal target enters this field, the electromagnetic energy creates eddy currents on the target object.

Eddy currents are circular-moving electrical currents that are created when a conductive material is exposed to an alternating magnetic field. These currents generate their own electromagnetic fields, which interact back with the primary field of the sensor and reduce its amplitude.

This change in amplitude is detected by the oscillator circuit and an output signal is generated accordingly, in a special circuit that includes a Schmitt trigger. This output signal is then used to trigger a relay or an alarm, depending on the application of the sensor.

Inductive Proximity Sensor Range

The inductive proximity sensor range varies depending on the sensor type and size. Generally, small sensors have a short range while large ones can detect objects at greater distances.

Typical inductive sensor can pick objects that are within a few to 60 mm away. That said, there are special types of sensors that can offer longer ranges.

Several factors are considered when selecting the right inductive proximity sensor range. These include the size and shape of the target object, its material composition, and other things based on application.

Applications of Inductive Proximity Sensors

What is an inductive sensor used for, given that it can only sense metallic targets? Inductive proximity sensors suit applications that require reliable and contactless detection. So they’re widely used in industrial automation, robotics, consumer electronics, automotive and aerospace industries. Here’s a look at the materials that these sensors can detect, as well as how to use one.

What Can an Inductive Proximity Sensor Detect?

Inductive sensors are best suited to detect metals, and especially ferromagnetic materials and conductive objects. Depending on the material of the target object, you can also use them to detect iron, steel, aluminum and other metals.

How to Use an Inductive Proximity Sensor

You can use proximity sensors in many different situations. The inductive type, in particular, is useful where it’s important to detect the presence of a metallic object. Some common inductive proximity sensor applications include:

  • Automotive Body Recognition
  • Position Detection for Industrial Machinery
  • Process Automation
  • Robotic Guidance
  • Object Detection in Security Systems

When choosing the right inductive proximity sensor, it helps to consider the various factors that affect its performance such as target material composition and size of the sensing area. Different models may also come with different levels of sensitivity, so you have to choose one based on your needs.

Capacity vs. inductive proximity sensor
Capacity vs. inductive proximity sensor

Capacitive Vs. Inductive Proximity Sensor

What is the difference between inductive and capacitive proximity sensors? Both are non-contact sensing devices. However, they use different methods to do so. Here is what you need to know about these types of sensors:

  • While an inductive sensor uses a magnetic field to detect metal objects, a capacitive one senses changes in the electrical properties of its environment. To enable that, it sends out an electrical field using an oscillator circuit.
  • A decrease in the field strength is detected when a conductive object comes into contact with the sensor.
  • The inductive proximity sensor range is usually longer than that of a capacitive one. Moreover, inductive sensors are better suited for detecting ferromagnetic objects and those made from conducting materials.
  • On the other hand, capacitive sensors are better for detecting non-metallic objects such as plastics.

Therefore, whether to use an inductive or capacitive proximity sensor depends on the application: an inductive for metal objects and capacitive for non-metallic materials or both metals and non-metals.

Different inductive proximity sensors
Different inductive proximity sensors

Inductive Proximity Sensor Cost

If you intend to buy inductive proximity sensor or sensing devices for your project, you may want to know how much you’re likely to step. The inductive proximity sensor price generally lies in the range of $15 to $50 for most basic models. More complex models with higher features can cost up to (or more than) $100.

The inductive proximity sensor price depends on its range, the type of material it can detect, and the sensitivity level. Prices may also vary depending on the vendor or manufacturer.

That said, these types of sensors are relatively inexpensive when compared to other types of sensing solutions. As a rule of thumb, the more features you get in your sensor, the higher its price.

To make a well-informed decision when selecting an inductive proximity sensor for your application, our advice is that you choose what will work for your needs the best. That means considering factors such as sensing range, environmental condition, target size, and more.


The inductive proximity sensor is one of the most popular types of non-contact sensors today, with its wide range of applications. From automotive body recognition to robotic guidance, these sensors offer a reliable and cost-effective solution for detecting metallic objects without physical contact.

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I am William, Electrical Engineering Author. Dedicated to writing technical articles on Timer Relay, Monitoring Relay, Surge Protection Device and other electrical devices. With 7 years of writing experience, I am committed to providing accurate and in-depth expertise to my readers.


    Thank you, very helpful.

    Merci, très utile pour des recherches.
    MAIS j’aurais aimé un peu plus l’article si vous allez en détail dans l’explication des différentes composante(oscillateur, bobine, …)

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