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New to DSO's, specification advice needed. (I've been out of the game a while!)

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Harrow:
I've always worked with analog Tektronix CROs. I now need to get a DSO to work on SMPS in the low kW range. I really have no idea what DSO specifications are required for accurately capturing the bridge transistor ringing and switching transients. My budget is relatively low but potentially flexible, so I'd be happy to understand minimum requirements, but also 'nice to haves'.

Any advice would be greatly appreciated.  Thank you!

David Hess:
I think any "modern" DSO will be suitable, with modern including DSOs going back 40 years.

I would be more concerned with the probes, and having a high voltage differential probe to make floating measurements, or a DSO which has galvanically isolated inputs so it can make these measurements directly.

Harrow:
Thanks, I'm familiar with measuring floating bridge voltages as I used to do work in this area some 30 years ago, so no problem there. It's really the digital sampling rate and bandwidth figures that I was wondering about since all my experience is with analogue equipment. For example, I wasn't sure if 100 MHz BW and 1GS/s shared between channels would be sufficient for capturing the transients and ringing accurately, or would I need something better?

Here are my rough thoughts on the subject, but I have no idea if my logic is correct or way off. To be working with rise times in the order of 10ns, that's around 100 MHz, so I figure a 200 MHz -3dB point would give me reasonable measurements there, and working on the basis of sampling at 10x the 10 ns to get accurate transient waveforms would mean 1GS/s, but since that gets shared between channels, then ideally that would be 4GS/s when shared between 4 channels? That sounds like maybe I could get away with something like a RIGOL 900 and just use 2 channels when it matters?

ebastler:
There are a lot of differences between digital and analog scopes, but input bandwidth works pretty much the same on both. So if you were happy with 100 MHz on your analog CRO, it should work just as well on a DSO.

Sampling rates of 3x bandwidth are considered adequate today, since DSOs can do proper sin(x)/x reconstruction of traces. 5x bandwidth puts you on the safe side. So 100 MHz with a shared 1 GSa/s is perfectly fine for 2 channels, and a bit marginal if the sampling rate is divided over 4 channels.

The Siglent SDS814X HD is about to be launched in Western markets. For a rumored price of $499 it has a 12-bit A/D converter and 2 GSa/s shared across up to 4 channels, at 100 MHz bandwidth. (There is also a 200 MHz "824" version, noticeably more expensive at $699.) And it will offer a "power analysis" software option at extra cost, which is unusual in this entry-level segment. The following threads provide more detail about this new series than you ever wanted to know:  ;)

https://www.eevblog.com/forum/testgear/sds800x-hd-review-demonstration-thread/
https://www.eevblog.com/forum/testgear/siglent-sds800x-hd-12-bit-dsos-coming/

If you prefer a 10" screen, the companion SDS1104X HD will be launched at the same time, at a significantly higher price ($1099?).

tszaboo:
DSOs are nice for such work, but you should really budget in some money for these two things:
AC/DC current clamp
Differential high voltage probe

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