A large Micro Electronic Mechanical System (MEMS) manufacturer measured the resonant frequency of the internal beam that measures acceleration by driving the beam with a pseudo-random signal that would allow the beam to vibrate at its natural resonant frequency. I duplicated their test with the Nextest Lightning but did it 4 times faster and used a few tricks to clean up the resonant spectrum. The upper spectrum is what the manufacturer got on his own home-brew test system. I then used a trick to do noise shaping and finally used an FIR to smooth the spectrum to show the true peak resonant frequency with higher accuracy than the manufacturer was used to. Note that the peak of the smoothed and shaped spectrum is a little lower in frequency than the non-smoothed result. This is the most accurate answer and thoroughly impressed the chip maker.
