Fundamentals of Inductive Sensors

Sensors play a critical role in various industries and applications, including in the world of micro motion industry. Inductive sensors are of particular note due to their unique ability to detect the presence or absence of vital motor-related components like magnets, coils, and stators without the need for physical contact for position sensing, speed monitoring, and object. In this blog, we'll explore how inductive sensors work, their types, and their components.

How Inductive Sensors Work

An inductive senor is an electronic device designed to detect motion system components like magnets, rotors, stators, and coils without physical contact with the components. The sensing range of an inductive sensor is the distance from the sensor’s face to the maximum distance the sensor can detect a metal target.  When a coil or wire, usually made of ferrite or another magnetic material, is wound around a core, it operates based on the electromagnetic principle. When an alternating current (AC) flows through this coil, an electromagnetic field is generated.

Inductive sensors working principle

When a metallic motor component enters the sensor’s proximity, it disturbs this electromagnetic field; this induces eddy currents within the metal object, which in turn creates its own magnetic field. The presence of this secondary magnetic field alters the inductance of the sensor coil, causing a change in its output signal.

Components of Inductive Sensors

The below block diagram represents the basic components and flow of information within an inductive sensor. Actual implementations may vary depending on the specific design and application requirements.

The inductive coil is the main sensing element of the inductive sensor. It consists of a coil of wire wound around a core. When an alternating current (AC) flows through this coil, it generates an electromagnetic field.

• The oscillator circuit generates the alternating current (AC) that is fed into the inductive coil. It ensures a stable and consistent frequency for the electromagnetic field.
• The signal conditioning circuit processes the signal induced in the coil due to the presence of a metallic object. It may amplify, filter, or otherwise modify the signal to make it suitable for further processing.
• Output processing circuits interpret the conditioned signal to determine the presence or absence of a metallic object. It may include threshold detection, signal comparison, or other algorithms to make this determination.
• The output signal indicates the presence or absence of the metallic object. It can be in the form of a digital signal (e.g., high/low voltage) or an analog signal (e.g., voltage level proportional to the detected object's distance). This signal can be used to trigger various actions in the system, such as activating alarms, controlling machinery, or providing feedback to a control system.

Types of Inductive Sensors

Inductive sensors come in various forms and serve different applications and requirements. Common types of inductive sensors are described below:

1. Proximity Sensors. These sensors detect the presence or absence of objects within a certain range without physical contact. They are widely used for object detection, counting, and positioning. The sensing range of an inductive proximity sensor changes based on the type of metal being detected (stator, rotor, coil, etc.). Since non-metallic substances such as dirt and liquid do not interfere with the detection, an inductive proximity sensor can operate in wet or dirty conditions.
2. Eddy Current Sensors. These sensors utilize the eddy currents induced in conductive materials to measure parameters such as thickness, conductivity, material composition, displacement, and position. They are commonly used in non-destructive testing (NDT) applications for quality control and defect detection.
3. Position Sensors. Inductive sensors can also be employed for precise position sensing in various mechanical systems, such as pneumatic cylinders, actuators, and machine tools.
4. Inductive Loop Sensors. Inductive loop sensors are used for vehicle detection in traffic management systems, toll booths, and parking facilities.
5. Eddy Current Displacement Sensors. These sensors measure the displacement or distance between the sensor and a conductive target by detecting changes in eddy currents induced in the target material. They are used in precision positioning, vibration monitoring, and quality control applications.

Application Examples

As mentioned above, inductive sensors are found in a wide range of applications. These include:

Aerospace Aircraft landing gear system Aircraft positioning systems Aircraft structural health monitoring Engine monitoring and control Environmental monitoring Flight control systems Ground vehicle position and navigation Magnetic field detection Maintenance and diagnostics Navigation and monitoring Weapons systems

Industrial Power Tools Jam and collision detection Material detection Robotic arm positioning Tool detection and verification Tool position and alignment Tool status monitoring Safety interlock Speed and rotation monitoring

Medical Biomedical research Bone cutting and drilling hand tools Implantable medical devices Infusion pumps Magnetic Resonance imaging (MRI) safety Motion tracking for training and assessment Patient monitoring systems Proximity detection in surgical instruments Surgical robots Tool recognition and identification Wireless charging in medical devices

 

Inductive sensors play a crucial role in modern sensing technology due to their reliable and precise detection capabilities across diverse applications. Have questions about inductive sensors? Our experts are more than happy to assist!