MathCAD FFT Amplitude

[REBJ]

I've been working on this FFT transform and I can't seem to get the right amplitude out. The frequency is correct, but the amplitude is about 1/3 of what it should be. The FFT was also done in LabView where it seems to be correct. Does anyone know if the amplitudes for MathCAD are scaled down by some number?

 

[GregLocock]

Yes. The scaling is specified in the help.

Even if it wasn't, it is always wise to generate and analyse a unit amplitude test signal when using a new fft routine, I think last time I counted I could think of 4 different scaling conventions.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[REBJ]

Thanks. I think I've figured out the problem. It talks about scaling the FFT by 2, but it wasn't coming out right still. I think it's de to the ratio of samples to input frequency. It has to be an integer to come out right.