On Fri, 2012-11-09 at 06:10 -0800, GMVoeth GM wrote:
> Hello PSN,
> 
> I know with a velocity sensor the voltage increases with frequency after 
> F0 if given the same
> vertical motion amplitude. This seems to be because as the frequency 
> increases
> so does the velocity and thus, the voltage output.
> 
> This means to me the energy also increases as the square of the velocity.
> So like, double the velocity, quadruple the energy.
> 
> What i would like to do is: filter at f0 (1.0Hz) so that given
> a steady shake amplitude (sine wave) but incresing frequency
> that the voltage will remain constant.
> 
> Now I understand this may not be possible.

I think it is.  A simple RC low pass filter (R from signal to C, C to
ground, output at junction of R and C) gives:

  T(S) = 1 / (R*C*S + 1)

Above w = 1/(R*C) this is

  T(S) ~ 1 / (R*C*S)

exactly what you need to reduce gain proportional to frequency.

For your example, w = 2*pi*1Hz = 1/RC so C = 1ufd, R = 160K should work.

-- 
Bob Smither                                 bob@...........
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        We're running out of boxes ... 
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