For this kind of cantilever, relation 1 gives a total mean (rms) fluctuation of 100 pm . Figure 4 shows the the spectral noise measurement of the cantilever movement acquired with the digital locking amplifier[29]. To characterize the spectral noise density and to discriminate thermal noise against other (technical) noise sources this data is fitted to the function The Lorentzian function is used to describe the thermal noise density of the cantilever, and the constant n 0 tec is introduced to describe any additional (technical) noise (see also [9, 35]). ¿From the fit to the experimental data, a quality factor Q = 100 ± 1, a natural frequency ν$_{0}$ = 79 . 440 ± 0 . 002 kHz , a thermal noise density α$_{th}$ =26.4 ± 0 . 2 fm/ √ kHz and a constant n 0 $_{tec}$=17 ± 2 fm/ √ kHz is found. The inset of figure 4 shows the total noise as a function of bandwidth, with the central frequency of the noise measurements at the resonance peak. In this log-log plot the square root dependence of the total noise on bandwidth for small bandwidth is clearly recognized from the slope m = 1 / 2. For high bandwidth, the total noise saturates. This saturation oc- curs for a bandwidth of the order of the width of the resonance curve Δ ν = ν$_{0}$/Q ≃ 0 . 8 kHz , in good agreement with the discussion above (relations 12 and 15) and the data obtained from the spectral noise density. We note that the saturation of noise is only observed if other noise sources are negligible, which is clearly the case in our measurements. Then, as the bandwidth of noise measurement is increased only the thermal noise in the resonance peak is “seen” by the DSFM detection unit. If other noise sources are not negligible, then, as the bandwidth of the DSFM detection unit is increased ( bw > ν/Q ), the detection unit will “see” this additional noise and the total noise will not saturate. Instead, it will continue to increase with the square root dependence known from the literature[37]. If the technical noise is appreciable, a total noise well above the theoretical value Δ a$_{th}$ = $^{√}$kT/c for thermal noise can be experimentally observed since thermal and technical noise is measured. Finally, figure 5 shows the noise of the frequency as a function of oscillation amplitude. Two different regimes are recognized: a constant regime for low oscillation amplitude where the total noise is independent of oscillation amplitude and a second regime where, as evi- denced by the slope m = − 1 in the log ( noise ) vs. log ( a$_{os}$ ) plot, the noise decreases with the inverse of the oscillation amplitude. The transition range of this graph corresponds to an oscillation amplitude $^{√}$kT/c ≃ 100 pm , in good agreement with the value for the thermal 12 f ( ν ) = α$_{th}$ $^{√}$(1 − ( ν/ν$_{0}$ ) $^{2}$) 2 + (( ν/ν$_{0}$ ) /Q ) 2 + n 0 tec