A basic inductive speed sensor, also known as a proximity sensor or an inductive proximity sensor, is a device that detects the speed of rotating equipment by utilizing electromagnetic principles. These sensors are commonly used in various industrial applications to monitor the speed of rotating machinery, such as motors, conveyor belts, and other equipment.
Here's how a basic inductive speed sensor works:
Principle of Inductance: The sensor operates based on the principle of inductance. When a conductive object moves within the sensing range of the sensor, it affects the electromagnetic field around the sensor's coil.
Sensor Construction: The sensor typically consists of a coil of wire wound around a core. This coil is connected to an oscillator circuit. The oscillator generates a high-frequency alternating current that flows through the coil.
Target Object: The rotating equipment that you want to measure the speed of should have a metal component or a target object made of a conductive material. This target object could be a metal gear, a blade, or any other rotating part.
Eddy Currents: As the target object rotates and comes closer to the sensor, it interacts with the sensor's electromagnetic field. This interaction induces eddy currents (localized circulating currents) in the target object due to electromagnetic induction.
Damping Effect: The eddy currents induced in the target object create their own magnetic field. This magnetic field opposes the original electromagnetic field generated by the sensor's coil. As a result, the original electromagnetic field around the sensor's coil gets dampened or weakened.
Frequency Shift: The oscillator circuit in the sensor continuously generates the alternating current. However, due to the damping effect caused by the eddy currents, the frequency of the current changes. The amount of frequency change is directly proportional to the speed of the rotating equipment. Faster rotation results in a greater frequency shift.
Signal Processing: The sensor's circuitry detects the frequency shift and converts it into an electrical signal that corresponds to the speed of the rotating equipment.
Output: The sensor's output can be in the form of a voltage signal, a current signal, or a digital signal (pulse) that represents the speed of the rotating equipment.
Calibration and Scaling: To accurately convert the frequency shift into speed units (such as RPM, revolutions per minute), the sensor might need to be calibrated and scaled based on the specifications of the equipment it's monitoring.
It's important to note that the sensing range, sensitivity, and characteristics of inductive speed sensors can vary based on their design and intended applications. These sensors are popular due to their durability, non-contact nature (no physical contact with the rotating equipment), and suitability for various industrial environments.