[sdiy] What test gear do you use?

[Michael E Caloroso]

Speaking of horrid interfaces, a letter I wrote to Bob Pease back in
2000 got printed in his column in Electronic Design magazine.  I'm
amazed that letter still survives on the internet since then.

http://www.rako.com/Other_Voices/Needless_Complexity/Needless_Complexity.htm

MC

On 5/10/18, rsdio at audiobanshee.com <rsdio at audiobanshee.com> wrote:
> My apologies. It appears that I haven’t used the Rigol, either.
>
> I just contacted my client, and the ‘scope that gave me so much trouble was
> the Agilent Technologies DSO3202A, 200 MHz, 1 GSa/s Digital Storage
> Oscilloscope. That’s the one with such horrible encoder tracking that I
> found it unusable.
>
> I must have somehow conflated the horrible practice of hacking the cheap
> Rigol to exceed the specifications of its front end with the horrible
> experience I had with the Agilent.
>
> Brian
>
>
> On May 7, 2018, at 9:03 PM, rsdio at audiobanshee.com wrote:
>> I have never seen an Owon scope at any of my clients’ facilities, so I
>> won’t be able to give one the ol’ Rigol test.
>>
>>
>> But you don’t need me, you can try the following for yourself:
>>
>> 1) Start with a circuit that has some kind of DC offset, preferably an
>> offset that you can vary, although not necessarily continuously - two
>> options will suffice. Maybe something with a virtual ground.
>>
>> 2) Connect a probe to this DC value and manually crank the gain on your
>> ‘scope until you can measure the noise floor on that signal. You’ll need
>> to adjust the Position to keep the signal on the screen at high gain since
>> it’s not centered around 0 V.
>>
>> 3) Now, make a change to the circuit that shifts the DC bias elsewhere.
>> With the high gain from step 2, this DC change should move the signal
>> trace well off of the screen. Try adjusting the Position again until the
>> signal is back in view.
>>
>>
>> With any decent ‘scope, these steps are not difficult. You intuitively
>> change the Position knob quickly until the signal is visible somewhere on
>> the screen, and then you slow down your adjustments and perhaps reverse
>> direction until you get close to the desired reticle. Your adjustments
>> will naturally get slower and slower and you make finer and finer
>> adjustments.
>>
>> With the Rigol, steps 2 and 3 can be impossible. Turning the Position knob
>> at a medium speed seems to take forever, and the signal doesn’t ever
>> appear on the screen. Continued adjustment eventually results in an
>> overshoot. Slow or fast turns of the Position encoder simply do not behave
>> as expected. There are sudden jumps in the signal on the screen. There
>> seem to be three modes: painfully slow, ridiculously fast with overshoot,
>> or sudden changes between the extremes. As I said, I found the Rigol to be
>> unusable.
>>
>> I’ve sent a message to my client asking what model Rigol ‘scope they have
>> so I can find out whether it’s the same model you guys seem to love so
>> much. My client is not exactly strapped for cash, they purchased their
>> Rigol new, and they have not made any of the popular hacks. It’s probably
>> a firmware design fail, or perhaps bad signal conditioning on the
>> encoder(s') phase signals.
>>
>> Brian
>
>
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