A basic inductive speed sensor, also known as an inductive proximity sensor, is a type of sensor used to detect the speed of rotating equipment. It works on the principle of electromagnetic induction and is commonly used in industrial applications for monitoring and controlling machinery speed. Here's how it typically works:
Principle of Inductive Proximity Sensing: An inductive speed sensor generates a magnetic field around its sensing face. When a metallic target, such as a gear tooth or a piece of metal attached to a rotating shaft, enters the sensing range of the sensor, it disturbs the magnetic field. This disturbance is detected by the sensor, allowing it to determine the speed of the rotating equipment.
Eddy Currents: As the metallic target passes through the sensor's magnetic field, eddy currents are induced in the metal. Eddy currents are circular electric currents that flow within the metal due to the changing magnetic field. The presence of these eddy currents alters the impedance of the sensor's coil.
Change in Inductance: The inductive speed sensor contains a coil that is part of an oscillator circuit. The disturbance caused by the eddy currents changes the inductance of the coil. This alteration in inductance affects the oscillator frequency or amplitude.
Signal Processing: The sensor's electronics process the changes in frequency or amplitude caused by the varying inductance. The processor can then convert these changes into a digital signal that represents the speed of the rotating equipment.
Output: The sensor's output can be analog (voltage or current) or digital (pulses or frequency). The frequency of the output signal is directly proportional to the speed of the rotating equipment. This signal can then be used by control systems, displays, or other equipment for monitoring and control purposes.
In summary, a basic inductive speed sensor detects the speed of rotating equipment by generating a magnetic field and sensing the disturbances caused by eddy currents induced in a metallic target as it enters the sensor's field. This disturbance is then converted into an output signal that represents the speed of the rotating equipment. It's a simple and effective way to monitor rotational speed in industrial applications.