[time-nuts] Chinese Scopes

J. Forster jfor at quikus.com
Tue Apr 17 14:30:32 UTC 2012


IMO, memory depth is like trying to do CAD on a standard computer
monitor...  you keep having to switch between the local and global views
to do really anything. I find it annoying in the extreme.

IMO, you need enough memory depth so that you don't get artifacts, like
those in the pics I posted. No 465 would mess up the waveform that way,
and remember, that was of a LORAN-A pulse for a system that was designed
before most of us were born and that ceased operation over 40 years ago...
 not a current design.

-John

================



> I agree that memory depth is an under appreciated parameter, but even
> 2,500 points like what's available on the cheap Tek scopes is quite
> useful.
>
> On the other hand, I had a few LeCroy with 50k deep memories and there are
> cases where that is very useful too. I can't imagine real life use cases
> when I would need multiple MB. It would be nice to have but seldom used.
>
> One issue is that most DSOs don't have displays that let you take
> advantage of the higher memory depth other than by letting you zoom in on
> a narrow time window. I have found that on the TDS 200 and 2000 series,
> downloading the data to a PC will let you display and print higher
> resolution pictures and I wrote a utility to do that.
>
> Didier KO4BB
>
> Sent from my BlackBerry Wireless thingy while I do other things...
>
> -----Original Message-----
> From: "J. Forster" <jfor at quikus.com>
> Sender: time-nuts-bounces at febo.com
> Date: Mon, 16 Apr 2012 13:58:09
> To: Discussion of precise time and frequency
> measurement<time-nuts at febo.com>
> Reply-To: jfor at quikus.com, Discussion of precise time and frequency
> measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Chinese Scopes
>
> OK. IMO, there is another, perhas a more important, issue....  memory
> depth.
>
> Most digital scopes I've seen, and some LAs too, just don't have enough
> depth for my taste, so they undersample and guess.
>
> Tek did make the RTD-710A high speed transient data digitizer that had 64
> MB of 12 (?) bit RAM. That is beginning to be useful, IMO.
>
> -John
>
> ==================
>
>
>> Sorry john, that's more what I meant, by accuracy and precision I imply
>> its faithful to the signal you choose to examine, free of artifacts
>> induced by the scopes timebase or vertical amp, but with DSOs its
>> limited
>> by Nyquist sampling rules.
>>
>> Thus, sampling rate is as important a feature as a scopes rated
>> bandwidth.
>>  For best results, its should be 10x the analog bandwidth.  Below it,
>> one
>> has to beware of artifacts, it worsens as the ratio signal bandwidth/
>> sampling rate < 10.
>>
>>
>> At 14:32 04/16/2012, time-nuts-request at febo.com wrote:
>> ------------------------------
>> Message: 2
>> Date: Mon, 16 Apr 2012 10:59:16 -0700 (PDT)
>> From: "J. Forster" <jfor at quikus.com>
>> To: "Discussion of precise time and frequency measurement"
>>         <time-nuts at febo.com>
>> Subject: Re: [time-nuts] Chinese Scopes (was: Re: LORAN-C at MIT)
>> Message-ID: <56387.12.6.201.2.1334599156.squirrel at popaccts.quikus.com>
>> Content-Type: text/plain;charset=iso-8859-1
>>
>>> At eevblog.com forum Chinese scopes are a daily discussion for over 3
>>> years.
>>>
>>> In summary, in the <= 100 MHz level they are ...
>> ...snip...
>>>... less.  The criteria for rating them are
>>> measurement accuracy and precision, UI, construction quality and tech
>>> support.
>>
>> Measurement accuracy is a ruse, IMO. I don't care if a 'scope is
>> "accurate". I want the waveform to be a faithful representation of the
>> electrical behaviour of the circuit, free oif sampling artifacts and
>> aliasing.
>>
>> If I want to accurately measure a voltage, I'll use a differential
>> comparator or DVM. Anything timing, an appropriately gated counter.
>>
>> Some years ago Tektronix had a digital camera package with RS-170 output
>> and some aardvaark frame grab board for a PC and a SW package. It was
>> designed to do waveform measurement.
>>
>> I would actually like to know why many seem to feel that a 500 MHz
>> analog
>> 'scope is not "good enough" for what you really do in your lab?
>>
>> The more I hear about 40 GSps or whatever 'scopes, the more I'm
>> convinced
>> it's like comparing car engines or top speed. So, I have a car that'll
>> do
>> 160 MPH and yours will do 172? So what? Can you use it? No.
>>
>> YMMV,
>>
>> -John
>>
>>
>> Best Wishes,
>>
>>
>> Marv Gozum, Philadelphia Pa
>>
>> [ sent via Outlook webApp]
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
>>
>
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>





More information about the time-nuts mailing list