Signal analysis

[WIM32]

I'm using an PCB accelerometer with ICP (built in electronics) to measure vibrations.
I'm using a PC-based data-acquisition system make Iotech.
When displaying the measured amplitude spectrum, peaks at 5, 10, 15 Hz and so forth can be seen. When repeating the measurement, the peaks get less 'high' and eventually (after about 20 min.) the spectrum looks more or less reliable. How can this problem be solved? Can FFT or windowing be the problem?
Thanks in advance
Wim32

 

[GregLocock]

That depends on what you are measuring. I can think of at least one way to get that problem, where the initial reading is correct. For what it's worth it sounds more like an instrumentation or setup error than a windowing or FFT problem.

Can you describe what you are trying to measure?

If you send me the data (preferably the time history, but the spectrum would be OK) for the two times you mention I'll have a look. Use csv or txt output. Send it to greglocock at yahoo.com.au


Cheers

Greg Locock

 

[brin]

Are you measuring this "real time" or averaging?

 

[WIM32]

brin, I'm averaging