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Error reading THD+N

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Error reading THD+N

Postby 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
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Re: Error reading THD+N

Postby 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.
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Re: Error reading THD+N

Postby ithertz » Tue Feb 11, 2014 11:55 pm

Has this issue been resolved yet?

I ask because I am considering buying a 4262.
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Re: Error reading THD+N

Postby 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?
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Re: Error reading THD+N

Postby 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,
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Re: Error reading THD+N

Postby 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.
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Re: Error reading THD+N

Postby 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
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Re: Error reading THD+N

Postby 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.
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Re: Error reading THD+N

Postby 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?
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Re: Error reading THD+N

Postby 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.
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