Vibration shaker: electr. output power of piezodevice exceeds mechanical input power

beagles

1. The problem statement, all variables and given/known data
Hello, I did the following measurement:

A piezo element (mass approx. 50 gram) is fixed onto a vibration shaker
The force exert on the piezo, 0,124 N (rms) is measured with an impedance head
The vibration frequency (sinusoidal signal) is 142,4 Hz
The acceleration is measered as 0,35 m/s² rms.
The electrical output power of the piezo is measured as 1,42 mW


2. Relevant equations



3. The attempt at a solution
Calculated input power: 0,35*1/(2*pi*142,4)*0,124=0,04mW (=speed * force)
with the speed = integral of the acceleration and 2*pi*142 the angular frequency

So the input power is much smaller than the output electrical power, which is impossible, it seems to be a factor 1000 wrong? Does anyone see my error, or measured value that is abnormal? Thanks already!


I did post this in the introductory physics forum some weeks ago, but received no answer. Anyone here has some advice, it is much appreciated!