Hi

I am trying to carry out a impact hammer modal test on a space truss using a HP 35660A. The problem is that I just have the analyzer without any kind of documentation. Please if someone could help me out with the steps required to program the analyzer to get the Natural Frequency & phase.

I am trying to carry out a impact hammer modal test on a space truss using a HP 35660A. The problem is that I just have the analyzer without any kind of documentation. Please if someone could help me out with the steps required to program the analyzer to get the Natural Frequency & phase.

X-axis value in Hz.

The damping factor is computed by placing two markers, one to

right of the peak amplitude at a point that is 3dB below the peak

amplitude and one to the left of the peak amplitude at a point 3dB

below the peak amplitude. Then, you take the difference of the

marker frequencies and divide it by (2*natural frequency).

The damped natural frequency, Wd, is computed from the natural frequency, Wn (peak amplitude

frequency location) as follows:

Wd = Wn * sqrt(1-(zeta)^2) where zeta = damping factor