can your 'scope do this?
 

some microvolts into a Tektronix 5223 digitizer with 5a22n differential amplifier:

http://www.tech-diy.com/TestEquipment/5223.gif

No :(

say, that's pretty neat...
 

Yeah, well, well,

my scope has more buttons than your scope!

Hi, Jackinnj,

How can I get this picture on the scope? The upper is the basic sinewave, the lower is the distortion component, but they both appear at the same time at the same scope?

I guess not directly.

But how about this: Measuring three channel single sweep at 50 ms/div, and then zooming at the details without recapturing the signals to 200 µs/div :cool:

lumanauw, I believe you'll need some kind of filter to pick up the desired distortion component(s) and eliminate the fundamental.

Regards,
Janne

How to do it? First I tought it is done by somekind of scaled X - Y

use an active T-notch filter -- this will give you THD+N -- to just get THD you need to count the magnitude of each harmonic -- which you can do in DSP -- design of such a filter can be found on Texas Instruments and Analog Devices websites.

fwiw -- the USB1208FS and Softwire (or other software packages) can do this pretty easily.

the 5223 example shown at the start of this thread is a scope used for low noise applications -- while technically part of the 5xxx series of boatanchors it has many of the features of the 7xxx devices but the bandwidth is quite limited.