During PeakForce capture I set up the Peak Force Amplitude to a certain value = A.

PF-Amplitude is the zero-peak distance, i.e.the length of extension or retraction path.

So, in online force monitor I observe curves F(z) exactly in the given range of z = 0....A.

However, when I open the obtained *.pfc file in Nanoscope Analysis (v.150 or 1.60) the range of z dispacement in force curve plot is allways twice higher than the given A.

In Peak Force Tapping, the 'amplitude' indeed refers to the zero-peak distance value (or 'A' in Asin(wt)). Both the force curves displayed in realtime and the ones stored when using peakforce capture reflect this, in the same way (the total Z range covers 2*A).