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  3. Inductive sensors

Introduction to Inductive Sensors

Inductive sensors, including proximity sensors, are nowadays indispensable for industrial applications. As compared to mechanical switches they offer almost ideal conditions: non-contact operation free from any wear and tear, high switching frequencies, and accuracy. In addition, they are insensitive to vibration, dust, and moisture.

Inductive sensors are a type of proximity sensor and are devices used for proximity sensing and detection in various applications. They operate based on the principle of electromagnetic induction. These sensors generate a high-frequency electromagnetic field and detect changes in the field caused by the presence of a metallic or conductive object.

Principle of Operation

The core component of an inductive sensor is a coil, typically made of copper wire, that is energised with an alternating current. When an object enters the sensor’s detection range, it interacts with the electromagnetic field generated by the coil, causing a change in the field. This change induces a voltage in the coil, which is detected and processed by the sensor’s electronics, which in turn results in output either switching, analogue, or IO-Link. 

Advantages of Inductive Sensors

Inductive sensors, specifically inductive proximity sensors, offer several advantages in industrial and automation settings. One of their key benefits is non-contact detection, which means there is no physical contact between the sensor and the target object. This feature eliminates the need for mechanical parts or physical wear, resulting in increased reliability and durability. Inductive proximity sensors can also detect metallic objects without requiring direct line-of-sight. They can detect objects through non-metallic materials such as plastic or glass, making them suitable for applications where the target object may be concealed or inaccessible.

Inductive sensors, especially inductive proximity sensors are commonly used in applications such as presence detection, object counting, position control, and speed monitoring. They find extensive use in industrial automation, robotics, assembly lines, conveyor systems, and packing machinery.

The low measurement tolerances ensure reliable detection and enable high repeatability. The switching distance varies depending on the design. Large designs achieve switching distances of up to 120 millimetres. Inductive sensors are available for different types of installation: flush sensors are flush with a surface, and non-flush sensors protrude a few millimetres in order to achieve a higher switching distance.

The switching distance of inductive sensors, including proximity sensors, is subject to a correction factor, which is reduced for metals other than steel. ifm also offers special sensors with a correction factor of 1, these have the same switching distance on all metals.  

The Versatility of Inductive Sensors

A large operating temperature range and high degrees of protection make inductive sensors, including inductive proximity sensors ideal for the requirements in harsh industrial environments. The inductive sensors are characterised by their low permeability even in extreme applications with protection class ranges IP67/68 for immersion in liquids to IP69K for high-pressure washdown, for example in the food and beverage industries. There are a wide range of inductive sensors with temperatures as low as -40oC, and up to as high as 180oC. In addition, the devices are exceptionally resistant to temperature shocks. Inductive sensors can also be designed for both AC and DC voltage inputs, and their sensing range can be adjusted to meet specific application requirements.

The M12 connector is the standard when connecting sensors, including proximity sensors, because it offers quick, easy, and error-free installation. ifm also offers inductive sensors with cable connection. These are often installed in space-constrained applications. 

Summary of Inductive Sensors and Proximity Sensors

In summary, inductive sensors, including proximity sensors, are non-contact devices that use electromagnetic induction to detect the presence of metallic or conductive objects. They offer reliable and durable proximity sensing solutions for a wide range of industrial and automation applications, providing benefits such as non-contact detection, versatility, and suitability for harsh environments. Due to their wide range of possible uses and their reliability, inductive sensors are an important component in modern automation technology and are used in many branches of industry.