Test and Measurement Forum

Advice for plotting spectrum

Post your MATLAB discussions here

Advice for plotting spectrum

Postby cx1111 » Mon Jun 09, 2014 1:34 pm

Hello

I am collecting information via the picoscope. My aim is to apply a digital filter over it, and then plot : (spectrum of filtered signal) - (a fixed spectrum saved).

What I want is a real time fft, like the one shown in the picoscope 6 program, but I must process the data first so I need to use matlab instead.


-Gathering data is quite slow. Is the majority of the time taken up by ADC conversion? If I wanted to replicate the picoscope 6 spectrum via matlab, there would be a significant delay. Any suggestions?

-How does the picoscope 6 program show the real time fft? ie how many points does it use, what is the refresh rate, etc? I want to know so I can maybe base my matlab code on it.

Thank you very much.
cx1111
Newbie
 
Posts: 0
Joined: Thu Nov 28, 2013 12:57 pm

Re: Advice for plotting spectrum

Postby Hitesh » Tue Jun 17, 2014 12:19 pm

Hi cx1111,

Are you using one of the Instrument Driver packages to collect data into MATLAB?

If so, if you are using the PicoScope 3000 series examples, these have been updated to speed up the conversion from ADC counts and are now available to download from:

http://www.mathworks.com/matlabcentral/fileexchange/38952-picoscope%C2%AE-3000-series-matlab%C2%AE-generic-instrument-driver

Have you come across the MathWorks example of calculating and plotting an fft of a signal?

http://www.mathworks.co.uk/help/matlab/ref/fft.html

You could try calculating an FFT over a small number of points.

The PicoScope 6 software will determine how to produce the spectrum plot based on the settings used, using 3rd party libraries to optimise FFT calculations.

Regards,
Hitesh

Technical Specialist
Pico Technology
Hitesh
Site Admin
Site Admin
 
Posts: 2058
Joined: Tue May 31, 2011 3:43 pm
Location: St. Neots, Cambridgeshire


Return to MATLAB

Who is online

Users browsing this forum: No registered users and 0 guests