[time-nuts] Rigol scopes

[David]

I would agree that a DSO with a peak detect mode is the way to go for
general purpose work.  I just wish the cheap ones had delayed sweep
and faster waveform acquisition rates instead of long record lengths.

When I was diagnosing an offline switching power supply a few weeks
ago that was stuck in pulse mode, digital storage mode on my Tektronix
2230 saved the day.

On Thu, 19 Apr 2012 21:54:16 +0000, shalimr9 at gmail.com wrote:

>"A non-sampling oscilloscope with limited bandwidth could just as easily
>miss a narrow pulse because of bandwidth constraints no matter how
>high its sampling rate."
>
>That is the point of the thread. Even a wide bandwidth analog scope used to show a 500nS pulse at a 200Hz repetition rate will have a hard time, while any DSO worth the name will have no problem with it.
>
>Didier KO4BB
>
>Sent from my BlackBerry Wireless thingy while I do other things...
>
>-----Original Message-----
>From: David <davidwhess at gmail.com>
>Sender: time-nuts-bounces at febo.com
>Date: Wed, 18 Apr 2012 18:11:29 
>To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
>Reply-To: Discussion of precise time and frequency measurement
>	<time-nuts at febo.com>
>Subject: Re: [time-nuts] Rigol scopes
>
>On Wed, 18 Apr 2012 13:56:18 +0000, shalimr9 at gmail.com wrote:
>
>>That's why the default mode for a DSO should always be "pulse detect" or whatever the manufacturer calls it, unless you know what you are doing. As far as I know, all DSOs have this or an equivalent mode where the ADC runs at full speed regardless of sweep speed, and the min and max readings between two display points are stored. If you are in a condition that would otherwise result in aliasing, the trace will look like a big fat trace, just like on an analog scope if you are probing a 10MHz signal at 1mS/div.
>
>Do the low end Rigol oscilloscopes actually support peak detection?
>The manual only describes an envelope mode without any ability to set
>the number of envelopes like a Tektronix 2440 can for single shot peak
>detection.  When I was in the market for a DSO a couple years ago, the
>Rigol representatives could not answer.  I ended up rebuilding an old
>Tektronix 2230.
>
>>You get the same issue with an analog sampling scope, except that those don't have a "pulse detect" mode, so they WILL lie to you unless you know what you are doing. It is not a "digital storage" issue, it is a sampling issue.
>
>Sampling oscilloscopes are in a class all to their own and very
>specialized.  Their low sample rates hinder capturing infrequent
>events but if a repetitive glitch is there, they can still see it.  A
>non-sampling oscilloscope with limited bandwidth could just as easily
>miss a narrow pulse because of bandwidth constraints no matter how
>high its sampling rate.
>
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