Finding an accelerometer
Accelerometers are specified by the maximum accelerations they can measure.  You therefore have to calculate what acceleration is represented by moving 2 mm at 2 KHz.

From your description, 2 mm is the peak to peak magnitude of the 2 kHz oscillation.  Acceleration is the second derivative of displacement.  The displacement is (1 mm)sin(2&Pi;t 2000/s).  Take the second derivative, which will be another sine.  The peak of that is the &plusmn;magnitude the accelerometer needs to be able to measure.  Acclerometers are often specified in g instead of m/s2 or the like.  1 g = 9.8 m/s2.

Added

Now I have time to show the calculations.  The equation for displacement is:

&nbsp; &nbsp; Disp = (1 mm)sin(2&Pi;t 2000/s)

First derivative:

&nbsp; &nbsp; Speed = (12.57x103 mm/s)cos(2&Pi;t 2000/s)

Second derivative:

&nbsp; &nbsp; Acc = -(158x106 mm/s2)sin(2&Pi;t 2000/s)

The accelleration range is therefore &plusmn;158x106 mm/s2 = &plusmn;158x103 m/s2.

&nbsp; &nbsp; &plusmn;(158x103 m/s2)/(9.8 m/s2g) = &plusmn;16.1x103 g.