Electromagnetic Velocity Sensors
Electromagnetic velocity sensors are type of sensor that utilizes the law of electromagnetic induction (Faraday's Law) to directly convert vibration velocity into an electrical signal output. It does not require an external power supply and is a self-generating (power-generating) sensor.
Its core principle is: The magnitude of the electromotive force (EMF) induced in a closed circuit is proportional to the rate of change of the magnetic flux through the circuit.
Basic Structure and Working Principle
A typical electromagnetic velocity sensor mainly consists of the following components:
- Magnet: Provides a constant magnetic field.
- Coil: A conductor that moves within the magnetic field.
- Spring-Mass System: The core mechanical moving part.
- Proof Mass: Usually connected to the coil (moving-coil type) or to the magnet (moving-magnet type).
- Spring: Supports the proof mass and determines the system's natural frequency.
Operating Process
The sensor housing is fixed to the vibrating object being measured and vibrates with it.
Due to inertia, the internal proof mass tends to remain stationary or in its original state of motion.
Therefore, relative motion occurs between the housing and the proof mass.
This relative motion causes the coil to continuously cut the magnetic lines of force (or conversely, the magnetic lines are cut by the coil), thereby generating an electromotive force (EMF) across the ends of the coil.
According to the law of electromagnetic induction, the magnitude of this induced EMF is proportional to the rate at which the coil cuts the magnetic lines of force (i.e., the relative velocity).
Simple Summary: It directly converts "vibration velocity" into "voltage."
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