Test and Measurement Forum

2205 spectrum analy harmonic view incorrect

Post any questions you may have about our current range of oscilloscopes

2205 spectrum analy harmonic view incorrect

Postby richy » Wed Apr 14, 2010 5:20 pm

My 2205 has this peculiar behaviour of not showing the correct harmonics. One varies the input level and the f2,3,5 (ref 1Khz) all shoot up/down as if the input to the A/D converter is showing harmonics related to amplitude. No it's anti-aliasing- The input is well below warning exclamation. Whats the reason: poor decoupling on 2205 ?

Other instruments don't have this varying harmonic representation with input level. So in the field it's impossible to get the true picture.
Help !
richy
 

Re: 2205 spectrum analy harmonic view incorrect

Postby PeterF » Thu Apr 15, 2010 11:58 am

Hi,
I can't duplicate your problem here. Varying the input amplitude up/down causes the whole display to go up/down but all harmonics stay in the same proportion as they should. What settings are you using? What do you expect to see?
Regards,
Peterf.
PeterF
Zen Master
Zen Master
 
Posts: 435
Joined: Thu Jun 07, 2007 10:53 am
Location: Cambridgeshire

Re: 2205 spectrum analy harmonic view incorrect

Postby richy » Tue Apr 20, 2010 6:03 am

Peter, I've taken a couple of FFT's using the inbuilt sine generator with direct connection. I cannot post pics on this site so I will send them to the company main.
richy
 

Re: 2205 spectrum analy harmonic view incorrect

Postby PeterF » Tue Apr 20, 2010 11:51 am

Hi Richy,
I can see what the problem is now. You are looking for harmonics which are at a level 50dB lower than the fundamental signal. Since the 2205 input, and the AWG are both 8 bit, the maximum resolution possible is about 48dB.
Please read the following explanation:-
http://www.picotech.com/applications/resolution.html
To do what you want, I feel you will need a 12 bit scope like the 4224.
Regards,
PeterF.
PeterF
Zen Master
Zen Master
 
Posts: 435
Joined: Thu Jun 07, 2007 10:53 am
Location: Cambridgeshire


Return to USB PC Oscilloscopes

Who is online

Users browsing this forum: No registered users and 0 guests