[time-nuts] Chinese Scopes

Robert Darlington rdarlington at gmail.com
Tue Apr 17 14:15:21 UTC 2012


I need lots of memory on scopes.  A buddy of mine I worked with in the
ultrasound world actually yelled at the Tek product management and
asked if they actually *use* oscilloscopes.  The answer was a sheepish
no, and yet they felt qualified to develop the products for the
company.

The cheap Aktakom scope I have has plenty.  10 million samples (you
can select less if you want) and will write out to usb thumb drives.
It's definitely a toy scope with lots of noise, but it's useful for
some things.

What we do is send out pulses or chirps and look at what returns.
There are tens of millisecond delays between what we send out and what
we receive and the echos.    With traditional low memory scopes we
simply can't get by.  Thankfully Tek is learning that memory is cheap
and 2500 samples was hardly sufficient in the 70s, let alone now!

-Bob

On Tue, Apr 17, 2012 at 7:56 AM,  <shalimr9 at gmail.com> wrote:
> 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]
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>
>
>
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