Re: Why no delayed trigger on newer DSOs?

Fred Bartoli wrote:

Le Wed, 15 Aug 2007 08:54:43 -0700, Joerg a écrit:


Fred Bartoli wrote:


Le Wed, 15 Aug 2007 07:13:09 +0000, Joerg a écrit:



Rich Grise wrote:



On Mon, 13 Aug 2007 12:19:48 -0700, Joerg wrote:




Hello Folks,

Question: It seems that most portable DSOs in the 200MHz/1GSPS class
don't offer delayed trigger anymore which makes pulse-echo
measurements a real pain. Why don't they?

After all it's just a simple counter that is needed. Same for
hold-off which typically ain't there either :-(

Beats me but IIRC I used delayed trigger on a lower end TDS220
although its data *** said that it could not do it. However, that
scope had some other serious issues (noise) so I asked the client to
obtain a used 2265. Old Faithful, of course, always has delayed
trigger but sure enough the plastic clutch for that function fell
apart right away. Designing a trigger delay into an analog scope is
no small feat but for a DSO it should be really easy.


But, if it's a digital storage scope, why can't you just trigger it at
the beginning of the test and "zoom in" to the part you're interested
in seeing delayed?




Because the Instek runs out of memory after 25usec. Similarly priced
HPs run out in under 5usec and the Teks run out even earlier :-(



Right now, I have to do some really accurate compensation to a system's
step response. From the 10ns scale, down to the 100ms scale. What would
really be handy is a logarithmic sweep. That could easily be
implemented with say a sampling rate scaling down by a two factor while
time rises by a two factor.
Well, with GPIB and some post-processing it works, but it's much longer
and a bit... bulky.



The newer scopes such as this Instek allow data dumps via USB into the
PC at an amazing clip. Not realtime but close. When I want to do
something unusual with the data I use the CSV import into Excel.
However, I am not an expert (yet) in VBA so I can't do any processing
on-the-fly. But I'll learn it. Was hoping it was C and not Basic but, oh
well, I guess that was Bill Gates' decision.


Oh, it's not the transfer speed that lacks. For the few thousands points it's no pb. But then post processing is a pain: given I need about 1k averaging to reasonably get the signal out of noise, and the low rep rate and low signal level, the scope has enough time to drift between the superfast, fast, medium speed, slow and super slow acquisition so that I need to realign all the traces, resample to a log time scale. It'd be better if the fast and slow sample rates were done 'simultaneously'.


We seem to be working in very different fields then. Mine is mostly pulse-echo and other fast stuff. Often you have to catch some strange effect out of the corner of your eye. Like a transformer working up a DC runaway. Wait a few hundred milliseconds too long with some corrective action and the whole chebang can disintegrate with an impressive bang.

Looks like the carpet in the lab has had enough of that stuff. So I am mulling whether to put wood flooring in, and what kind of wood. Bamboo is all the rage right now in the US but it has a light color.

--
Regards, Joerg

http://www.analogconsultants.com
.

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