I found that my cheap Chinese AideTek x1/x10 100MHz probes which are
rated from 15pF to 35pF actually managed to barely make it to 47pF on
my 7A22.
For best performance, the probes used for differential measurements
should be matched in attenuation and frequency response. When you use
an oscilloscope in invert and add mode, you can use the VAR control on
one or the other channel to match the gain. With a differential
amplifier like the 7A13 or 7A22, attenuating probes really need to
have their own adjustment like with the Tektronix P6055 (20 MHz) or
P6055A (100 MHz).
I suspect the best option for the 7A22 if you can live with the extra
probe loading which is likely at 1 MHz and below is just to use x1
probes. Then there is no compensation or gain matching to worry
about.
On Thu, 28 Jun 2012 21:16:13 +0200, Fabio Eboli <fabioeb@...>
wrote:
Thank you for your input.
Even into the 7103 the 7A26 limited to 20MHz shows a
thin trace.
As for the 7A22 input capacitance, I have two of them
recently acquired, and only one old (cheap) 60MHz probe
compensates correctly. Probably I will try some ebay
cheap 60MHz probe batch to see if they will work, and hope
to find pairs that match. Is probes matching a problem?
Fabio.
David <davidwhess@...> ha scritto:
My 7603 (100 MHz) CRT has a lot of hours on it but comparing it to my
faster 7000 series oscilloscopes, I find that the plug-in matters more
than the mainframe as far as noise which is what I would expect.
The 7A12 (100 MHz) and 7A18 (100 MHz) both seem about the same on my
7905. The 7A13 (100 MHz/5 MHz) looks the same at 10mV/div and higher
but has more noise at 5mV/div because it uses a different internal
topology involving a switched x10 stage. The 7A16A and 7A26 (200
MHz/20 MHz) traces are slightly thicker which follows from their
higher bandwidth.
Switching in bandwidth limiting where available makes a huge
difference so where that matters, I use my 7A13, 7A16A, or 7A26. For
bandwidths up to 1 MHz the 7A22 should be the best of all but I do not
have a good set of probes yet that can be compensated to its 47pF
inputs.
On Thu, 28 Jun 2012 09:21:22 +0200, Fabio Eboli <fabioeb@...>
wrote:
Anyway I was saying that the noise is important
to me for an everyday scope, I was curious if
there was a source where I can control if a mainframe
has a fan or not.
Also as for trace thickness, I prefer remain confined
into the 7k series, the plugins flexibility is wondeful.
I imagine that it's easier for a lower bandwidth to
show a better defined trace, Is there any noticeable
difference in the 7k series ?
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David Hess