How good is your scope? (problem with capturing offset signals)

Klaus Kragelund wrote:
> On 2 Okt., 01:43, Joerg <inva...@invalid.invalid> wrote:
>> Klaus Kragelund wrote:

[...]


>>> As for the Tek DPO 5000, I dug deeper into it, and found that the
>>> majority of the problem (guess 70%) is actually from the TPP0500
>>> probe. A test with a P6139 probe provided much better results. We are
>>> returning those TPP0500 probes for sure...
>> Strange. How can a passive probe do that?
>>
>> --
>> Regards, Joerg
>>
>> http://www.analogconsultants.com/- Skjul tekst i anf&#4294967295;rselstegn -
>>
>> - Vis tekst i anf&#4294967295;rselstegn -
> 
> The datasheet lists it as a passive probe, but it is supplied with
> power, probably for some relays and other gimmicks they have inside
> the probe. When Volt/div is changed clicking can be heard, so its
> probably not a 100% passive probe, only it does not have an amplifier
> per se.....
> 

This would probably be the point where I couldn't wait any longer, crack
open the probe enclosures, and get into trouble :-)

There'd have to be some sort of semiconductor involved here. Maybe some
sort of limiter circuit?

-- 
Regards, Joerg

http://www.analogconsultants.com/

On Sat, 01 Oct 2011 16:09:26 -0700, Klaus Kragelund wrote:

> The Tek 7A26S module Joerg spoke of, has a definition of maximum 75
> times overdrive. Quite good, but the overdrive takes 100us to recover
> (worst case specs)

7A13 with attenuator set to 1mV per division recovers to within 2mV in
1us, and 1mV in 100us after a pulse of +/- 10V. (Per published spec)

And it does, too. Better, in fact, with the five I have around the lab,
and have personally calibrated. It's part of the performance check
procedure.

Effective offset range of 10,000 divisions.

I must try the same test with a 7A26. There's one that needs my attention
for unequal trigger delay between channels. Probably another of those
goddamn made-in-Tucson trimmer capacitors again. I'll try when I fix it.

-- 
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)