In Testlab Shock workbook, I was wondering if anyone could provide some insight into Pre Pulse Zero Padding (what exactly is it doing?) setting under “Advanced…”?
We have found that some of our Shock Tests start off with a lot of high frequency noise riding on the accelerometer signals (Blue Curve - It doesn’t seem to be coming from the UUT, as we see the same signature in our data even if we place the accels on a flat, thick, aluminum plate). Excuse the hand drawn curve.
But when we increase the Pre Pulse Zero Padding to be greater than 35%, most of the high frequency content seems to be removed from the signal…almost as if we applied a Low Pass Filter. There still seems to be some residual low frequency signal in the data (Red Curve).
We’re trying to determine: What exactly is Pre Pulse Zero Padding doing?...and Why does it remove the initial high frequency content?
Solved! Go to Solution.
The cause of the initial ringing is as follows:
Both effects are most noticeable in case the target pulse and ITF are high at low frequencies. A solution for these issues is to apply more zero padding.
With zero padding, time data values of zero are added at the beginning of the shock time trace. (magenta versus blue curve below). This helps reduce leakage and other effects that introduce ringing into the signal by making the shock signal more periodic.