Testing the monotonicity of a DAC

[erin]

If I want to observe on my oscilloscope, the monotonicity of a DAC chip,
I thought that if I generate a half sawtooth waveform using some audio software (like audacity etc.) with a duration of say 60 seconds, and the signal starting at -180 degrees crossing 0 degrees at 30 seconds and ending at +180 degrees at 60 seconds, I should be able to see any major non linearities as an unexpected increase or decrease in the DC voltage output of the DAC.

Can someone advise if this is a good way to do this or if there is a better way to do this test with a really good visual indication of non linearity.

Regards,
Erin

[Wayniac]

Great! The results of a two-channel subtraction (invert + add) plot would also be interesting to see.

[oshifis]

Actually I have done it:

DAC linearity test CD

This method tests Dynamic Non-Linearity. You can use the sawtooth method, but I am afraid you won't be able to see the 65536 steps on an oscilloscope, and what you will see is a straight line in any case.

[SoNic_real_one]

Originally Posted by erin

If I want to observe on my oscilloscope....with a duration of say 60 seconds...

Do you have a digital memory oscilloscope with linearity substantially higher than what you intend to measure?

[erin]

No, its an analog scope. I didn't want to "measure it", I just want to see some deviations.

I think the test CD by oshifis, should do the job.

Perhaps oshifis would be kind enough to explain how he generated the signals on his test CD?

[oshifis]

I used a hex editor