Error reading THD+N

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jane
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Error reading THD+N

Post by jane » Sun Mar 25, 2012 8:00 am

Here is a test of THD, THD+N and S/N measurements.
For this DUT 3HD is dominant at ~51dB below the fundamental that corresponds with the THD measurement.
But the THD+N reading has to be wrong: -96dB is the same as measured S/N -- where has the THD portion of the THD+N gone?
THD+N.gif
PicoScope® 6 - PC Oscilloscope software version: 6.6.18.8
Model: PicoScope 4262
USB Version: 2,0
Calibration Date: 19. januar 2012
Hardware Version: 1
Driver Version: 1.1.0.211
Firmware Version: 1.0.5.0 / 1.0.11.0

Martyn
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Re: Error reading THD+N

Post by Martyn » Tue Mar 27, 2012 12:57 pm

We are currently looking at the Picoscope 6 measurements as there may be a few inaccuracies with these.
Martyn
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ithertz
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Re: Error reading THD+N

Post by ithertz » Tue Feb 11, 2014 11:55 pm

Has this issue been resolved yet?

I ask because I am considering buying a 4262.

Audioguy
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Re: Error reading THD+N

Post by Audioguy » Mon Mar 31, 2014 1:53 pm

Any news on this?

I'm a long time user of Picoscope 3224 and I'm about to invest in a new scope - 4262 - for a workstation.

With a 16bit scope I'm happy to use it for Audio analsis but proper functions for distortin analysis is essential for a purchase.

Has this been fixed?

Karunen
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Re: Error reading THD+N

Post by Karunen » Mon Apr 14, 2014 3:40 pm

Hi Audioguy,

The issue has not been fixed in the current release,
but I will escalate this issue.

Thank you for your patience,
Karunen

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Pico Technology

Audioguy
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Re: Error reading THD+N

Post by Audioguy » Sat Apr 26, 2014 11:56 am

Thanks for reply.

This scope seems very nice for general audio work but proper distortion analyzis feels essential.

I use to use a high quality pro sound card but also a scope (3224) for analyzis. With 4262 it seems you can get by with one unit only but proper software functions is important. I also adressed the issue about the lack of log x axis in FFT mode for Picoscope.

Perhaps I'll invest in a 4262 and keep fingers crossed for improved software.

arshapro
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Re: Error reading THD+N

Post by arshapro » Thu Jun 26, 2014 8:15 pm

I'm also looking into a picoscop for audio work. Has the function generator issue been fixed - also I noticed another user was thinking of going with the 5242A because of the higher sampling rate. Also the function generator on the 5242A can go to 20Mhz - not that I would need to produce that frequency - however some claim that noise above 20KHz is audible to some people.

Are there some aspects of the 4262 that make it better for audio other than the 2 channel 16 bit operation whereas the 5242A has only one channel operation at 16 bit? Is the software the same?

Thank you!
-Alex

Martyn
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Re: Error reading THD+N

Post by Martyn » Mon Jun 30, 2014 7:01 am

The software is the same for both scopes, however the 4262 has been designed for audio work and has better performance in this range.

If you are looking for a scope for just audio work then the 4262 is the best choice, if you are looking for a scope that can do some audio work as well as other tasks then go for the 5242.
Martyn
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arshapro
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Re: Error reading THD+N

Post by arshapro » Mon Jun 30, 2014 3:38 pm

Has the function generator been fixed yet in the 4262? Also, I am interested in measuring the slew of different amps. This can require sampling down to 100 pico seconds. Does the 4262 do that?

Martyn
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Re: Error reading THD+N

Post by Martyn » Wed Jul 02, 2014 10:28 am

A fix has been introduced for the generator.

The maximum sampling rate is 10MS/s so 100ps sample interval is not possible with the the 4262, it is not even possible with the 5000 series devices which can go to 1ns at it's fastest.
Martyn
Technical Support Manager

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