Channel 2 FFT has peculiar vertical scale

[HarryNNelson]

Hi, for the captures below, first channel 1 and then channel 2 see a 1Vpp (500 mV amplitude) sine wave at 5.501 kHz... the Ch1 FFT looks right, but maybe the vertical scale on Ch2 is not accurate... it is labeled "Ch1" and the range is -1000mV to +1000mV, peak location not plotted at 500mV for Ch2... but in both cases the little tag reads the appropriate amplitude... for a while this has confused me as to what normalization the FFT used... pretty sure it is amplitude, not pp or RMS... but perhaps the display for Ch2 needs some analysis... best, Harry Nelson

Edited October 18, 2020 by HarryNNelson
slightly better text

[JColvin]

Hi @HarryNNelson,

I let the engineer much more familiar with WaveFormsLive know about this. They mentioned they have seen a similar bug before so hopefully this visual bug can be easily resolved.

Thanks,
JColvin

[HarryNNelson]

Thanks JColvin!  Presumably WaverFormsLive will just get changed in the "hot copy" we download eventually.

As long as I'm here, a similar effect in the Bode plot... I was thrown off by the label "Amplitude (dB)" in attached.

It appears to be "Amplitude^2", really... a factor of 2... maybe a better label might be "Power (dB)" or "Energy (dB)".

Having said that, we've had fun making the Bode plot work for resonant circuits... need to divide down the AWG.

best, Harry Nelson