Re: Tek 7623A (or 7000 series in general) - Poor man's choice to Signal Standardizer

Fabio Trevisan
 

Thanks Harvey,
My comments after yours (I suppressed my originals).
Rgrds,
Fabio

On Tue, 13 Mar 2018 12:34:46 -0700, you wrote:
I'd consider the following for this:
1) anything you can measure with a decent DMM is going to be far more
accurate than the eyeball can see on a trace and a grid. Unless you
have the 7D12, you don't have to worry all that much.
I fully agree, I failed to emphasize that on the Vertical dept. I'm more worried about AC and Step response. DC wise you're absolutely right that I can just compare the measurements with a DMM.

2) I'd consider a rail to rail op-amp that will run the right
voltages, then feed it with a decent square wave. If you needed less
than 15 volts p-p, you can feed a pair of CMOS gates (don't exceed the
limits for the power supply).
Two ways to do that, one is to have a "calibrated" variable power
supply for the +, and one for the -, connect the gate across those,
and level shift a decent squarewave. Another is to use a 10 volt
reference, run it through two op-amps to get + and - 10 volts, and
then much the same. I like the first one, myself.
Clear... It may worth to implement as I will be building something anyway... though all this will serve more the DC and linearity I think.

Something else to consider: The use for a signal standardizer is only
really valid when you want to have plugins moving from mainframe to
mainframe.
If you have one, then the combination of plugin gain and mainframe
gain is the only thing significant. You take a standard, and adjust
the plugin so that the measurement says, say, 10 volts. Then you
adjust all the other plugins to that.
If you can't, then you're off somewhere, and need to readjust the
mainframe gain in combination with the other plugins.
It *is* a lot easier with a standardizer, though.
However, with only one mainframe (if that's where you are), it really
doesn't make a difference.
You have a point there and indeed, I don't see myself having another 7xxx anytime soon or having any other Tek fan nearby with whom I could be swapping plug-ins.
Surely, I intend to have one or two additional vert Plug-ins (a 7A22 and, if luck smiles at me, another 7A26) but
the 7A22 should not pose problems to AC calibrate it, because at 1MHz, step response is not hard to come by and the - yet to exist - 2nd 7A26, I would need to calibrate it to match my 1st 7A26, much more than pursuing both to be "standard".

Well, DMMs are your friends.
Indeed. I`m counting on it for the DC accuracy.

2. Is it valid to think of my 2nd 7B53A "Ampl." function as a decent
"vanilla" pre-amp, feed it with a good pulse generator, take for granted
there's very little to be wrong in the TB's pre-amp and, therefore, consider
it a good "standard" to calibrate the MF's vertical?
I'm not sure that I'd like that idea.
I wasn't sure either (reason I asked), but now that you made me think that achieving good overall results may be more important (in my case of a stand-alone set), you know it may be a good idea?
Consider that a vertical plug-in has a lot of adjustments inside (that are more or less redundant with the MF's and -to some extent - can compensate for any MF's lack or excess in some department) and that the "Ampl" input signal path of the 7B53A has almost no adjustment...
Then, If I can get the MF to display the best square wave possible using the TB's "Ampl" input, and then adjust the Vertical Plug-in to match whatever the MF will end-up (as long as I have range, of course), will eventually make the best possible adjustment for the set I have at hand? Or not?

3. Is it a good idea to "tap" onto the output of the plugin (or conversely
the input of the MF), right at the MF's edge connector? On this same concept,
is it valid to look only at one side of the differential input signal?
An extender can save a lot of time and trouble.
and I'd be happier looking at the differential of the two inputs,
since that's what the scope is paying attention to.
You must be right in that, I don't believe I can rely on anything that I may be able to see single-endedly, specially in talking about step response.

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