Author Topic: Agilent MSOX3104A over-range weirdness  (Read 569 times)

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Offline taemun

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Agilent MSOX3104A over-range weirdness
« on: March 07, 2017, 01:29:58 pm »
I've been debugging a 24V -> 4V buck synchronous switcher, and noticed the voltage at the inductor input didn't look right. The first attachment shows what I see at 5V/div (the 24V peaks are just off the top of the screen), and the second shows the exact same circuit at 2V/div.

Clearly, the scope has difficulty recovering from something 12 divisions above the middle of the screen (ie, 8 divisions over-range)! Has anyone seen weird performance when observing strongly over-range signals on scopes? Should I just expect this?

 

Offline plazma

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Re: Agilent MSOX3104A over-range weirdness
« Reply #1 on: March 07, 2017, 01:32:04 pm »
Anything can happen with over range clipping signals. Don't do that.
 

Offline MarkL

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Re: Agilent MSOX3104A over-range weirdness
« Reply #2 on: March 07, 2017, 03:43:39 pm »
You're over-driving the front end amplifier.  It's always best to keep the pk-pk of the waveform on the screen.  On this particular waveform I think you're just over the limit.  If you move the offset down you should see the distortion decrease.

If you're actually trying to see the detail near 0V on this waveform, one method would be to first adjust the vertical gain to maximize the on-screen amplitude, turn on averaging, and then use the magnify feature.
 
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