Re: Calibrators vs Signal/Function Generators


Chuck Harris
 

When you are tweaking the 2465's vertical amplifier networks
to perfect the transient response, you can get into an area
where the pulse looks very nice and flat, with few ripples,
but, if you do a quick check on frequency response, you
will see that it is below specification by quite a bit...
Instead of 350MHz, it is more like almost 300MHz.

You can tell this is going to be true by other observations,
but the SG504 gives you a nice qualitative picture with a
couple of cranks of the dial.

You don't need to look at it all that hard, but if you set the
SG504 to 6 divisions p-p at 6MHz, and still get between 4.4
and 6 divisions in the range from 350MHz to 420MHz, you have
achieved the desired transient response... and not a false
response.

[You can also tell the false response because the leading edge
is thicker for the first division below the corner... indicating
that the rise time is slower there than it has to be. You want
that thick edge not to roll below about 0.1-0.2 divisions.]

The ultimate accuracy of the SG isn't all that important,
and indeed, I used a S-D synthesizer before I got my SG504, and
racing the two instruments shows no indication that the
synthesizer was doing a substandard job. Just that the SG makes
the test easier.

-Chuck Harris

David C. Partridge wrote:

Oops 3% isn't quite sub 0.1dB, but definitely small at 0.2567dB

David
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David C. Partridge
Sent: 14 July 2020 18:17
To: TekScopes@groups.io
Subject: Re: [TekScopes] Calibrators vs Signal/Function Generators

Weighing in here - the most common issue that you'll hit is that the flatness of the levelled sine wave generators is specified to a much higher standard than the typical levelled sig-gen.

For example the SG504 with levelling head accuracy specification is well down in the sub +/- 0.1dB area (within 3%) whereas a typical RF sig-gen is +/- 1dB

David
-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of David Berlind
Sent: 14 July 2020 15:14
To: TekScopes@groups.io
Subject: [TekScopes] Calibrators vs Signal/Function Generators

Question for the hive:

I have a pile of scopes here that I'll be looking to calibrate at some point as a part of their resurrection. I see that the primary function of some Tek calibration fixtures is to generate square and sine waves. How is this significantly different from what a well-calibrated signal/function generator can do?

Thank you.

David









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