Eddy current sensor: a coil at the end of the sensor, the coil with high frequency (1MHz ~ 2MHz) alternating voltage, when the coil plane near a conductor surface, the magnetic flux through the coil chain conductor, the surface layer induced by a conductor eddy current, magnetic flux and eddy current formed by the chain again through the primary coil, the primary coil and the eddy current coil was formed a coupling transformer, a primary coil inductance of the final feedback. The coupling coefficient is related to the distance between the two and the material of the conductor. When the material is given, the coupling coefficient is related to the distance, and it can be chosen as a linear section. So eddy current sensor is usually used to measure the displacement change of metal surface, also known as displacement sensor.
Speed sensor: usually consists of internal permanent magnet, support spring, coil, shell and signal cable. In general, the speed sensor is directly measured object and rigidly connected together; when the measured object vibration, speed sensor and measured object moving together, but because of the support spring speed sensor in the existence of the permanent magnet and the coil relative motion, so the coils, a speed sensor a small generator; the vibration velocity of the object more quickly, sensor output voltage is higher, the vibration speed is proportional to the output voltage.
Acceleration sensors: Accelerometer with a piezoelectric crystal plate, the acceleration sensor and the measured object is connected with the screw together, when the measured object vibration occurs due to the inertia effect will produce pressure on the deformation of the piezoelectric crystal plate, crystal surface or surface, it has the polarization charge generation, charge with the number of force generated is proportional to the size, so the piezoelectric sensor is acceleration sensor.
Composite vibration sensor: eddy current sensor and speed sensor are combined into one. The eddy current sensor is responsible for collecting the relative vibration between shaft and tile, speed sensor for the acquisition of sensor itself is absolute vibration tile. The absolute vibration of the rotating shaft can be obtained by adding the output vectors of the two sensors through the relevant circuit.
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