How Can We Measure Vibration Amplitude with an Eddy Current Displacement Sensor?

[NeeNee]

how can we measure the amplitude of vibration of a sheet with and eddy current displacement sensor?



my course work is :
how the time taken for the amplitude of vibrating sheet of aluminium to halve,varies with the magnetic flux density of the field in which the sheet is placed.
I wanted to know how does an eddy current displacement sensor or vibration sensor works?

 

[NeeNee]

I don need any1's help 'll find that myself...