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Meaning of % fs

by stephenx_86
Tags: % fs, frequency, meaning, noise, signal
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Oct16-13, 06:22 AM
P: 15

We're using a lock-in amplifier to oscillate an AFM-style cantilever (across a frequency sweep) and measure the response using a QPD. The aim of this is to see how the resonant frequency changes with changing environmental conditions.

The software we use ("ACQUIRE" by "Signal Recovery") is displaying this frequency response in terms of "Mag. (% fs)", which I assume is some sort of magnitude - maybe the magnitude of cantilever displacement? What we're least sure of is what exactly "% fs" means in this context. From looking round the internet it seems Fs is resonant frequency, but I don't know if this is the same Fs as the fs output by our machine! In the manual this is written as "MAG% (10V fs)", which might shed some more light on the situation.

If this actually is a percentage of the resonant frequency, does anyone know how resonant frequency is being calculated by the software? The spectra we get out (Mag (% fs) as a function of driving frequency (Hz)) is pretty noisy with no single, clear peak and goes up to ~300 (% fs).

If anyone could shed some light on what "% fs" is, we'd be really grateful.

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Oct16-13, 06:48 AM
P: 15,201
Percent full scale.

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