Block wave meassurement

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WouterS
Posts: 14
Joined: Wed Feb 18, 2015 9:58 am
Location: Merseburg/Diepenbeek

Block wave meassurement

Post by WouterS » Mon Feb 23, 2015 11:59 am

Hi everyone

I was meassuring some simple wave forms, and somehow i got a strange meassurement i generated a 53kHz block wave and
the meassurements look a bit different in matlab than the online meassurements is there a reason why it looks different?

http://postimg.org/image/6ntgcrf21/
http://postimg.org/image/ocl74dqt5/
http://postimg.org/image/kexxez3zt/
http://postimg.org/image/54y27s8hl/

These are the meassurements i get, i anyone knows a reason why they different, and could explain why they different? :)

Kind regards

Wouter

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Block wave meassurement

Post by Nils Roos » Mon Feb 23, 2015 7:54 pm

Hi Wouter,
One reason I can think off is that the MatLab call in clients/matlab/acquire.m does not use the shaping and equalization filter by default, whereas the scope app does.
You could try to add the "-e" and "-s" options to the MatLab script acuire call to see if that makes a difference. The line would read something like:

Code: Select all

...' "/opt/bin/acquire -s -e ',num2str(samps),' ',num2str(dec),' > /tmp/acq_tmp.txt"'...
All in a day's work for Bicycle Repair Man

WouterS
Posts: 14
Joined: Wed Feb 18, 2015 9:58 am
Location: Merseburg/Diepenbeek

Re: Block wave meassurement

Post by WouterS » Tue Feb 24, 2015 11:55 am

Alright it works now

Thanks! :D

WouterS
Posts: 14
Joined: Wed Feb 18, 2015 9:58 am
Location: Merseburg/Diepenbeek

Re: Block wave meassurement

Post by WouterS » Tue Feb 24, 2015 4:15 pm

Maybe another stupid question.. but is there a specific reason why the min,max,ptp measurements are different in matlab compared to the web application? I got close its only 50mV difference ( for each waveform) but maybe there is a reason why it keeps doing this..

Kind regards

Wouter

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Block wave meassurement

Post by Nils Roos » Wed Feb 25, 2015 12:00 am

This might have something to do with the calibration values, which the standard acquire utility ignores.

You could try the modified acquire from edgo, which applies calibration to the sampled values.
Bear in mind that the calibration in this utility is default off (so, another command line parameter) and that when switched on, the output values will be voltages, not raw samples.
All in a day's work for Bicycle Repair Man

WouterS
Posts: 14
Joined: Wed Feb 18, 2015 9:58 am
Location: Merseburg/Diepenbeek

Re: Block wave meassurement

Post by WouterS » Thu Feb 26, 2015 3:17 pm

Got it running :D Thanks for the hint.

Wouter

WouterS
Posts: 14
Joined: Wed Feb 18, 2015 9:58 am
Location: Merseburg/Diepenbeek

Re: Block wave meassurement

Post by WouterS » Tue Mar 03, 2015 10:52 am

Hello everyone

I walked into another problem. I am now trying to get measurements in labview with the -c command, but then when i try to convert the string to a numeric it rounds the values to 0.0 e+0. Anyone knows how i can get around this problem?

http://postimg.org/image/t0bii5vil/

Thanks in advance

Wouter

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