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-----Original Message-----
From: Miroslav Pokorni <mpokorni2000@...>
To: TekScopes@... <TekScopes@...>
Date: December 17, 2001 02:14 PM
Subject: Re: [TekScopes] Re: Capacitance standardizers



Since we are on standardizer subject and Dean brought up L/C meter, can
someone, please, tell me what is 'Inductance Standardizer for S-30' and how
it is used. The standardizer came with an old version of S-30, a transfer
standard for calibration of L/C meter Model 130. The version of S-30 is
conjured from the fact that it is in a two peace, deep drawn sheet metal
box, as opposed to later models that had 3 peace box, two cast end-caps and
sheet metal sides. The Inductance Standardizer itself is in a Pomona style
small box with RF connectors on ends and a switch labeled ???UP??? and ???DOWN???.
Inside, there is an old style silver mica cap (square, quite rectangular,
transfer molded body), an inductor (proper cross-hatch winding pattern),
couple of resistors that I can not determine value of and the switch.

It is quite possible that box is not a Tektronix product, but a shop brew,
since all marking are done with Dyno labels, while all other Tek boxes that
I have seen, would have at least part number silk screened on it.

My manual, a copy from original for instrument serial number 11000, does not
make any mention of the Standardizer, but then, it scarcely mentions
transfer standard, either.

Can someone, please, identify this box and tell me if it is a genuine Tek or
a shop brew, and in either case, how it is used.

deanhuster <dhuster@...> wrote: Morris, Stan's post is
deadly-accurate and will work well. The only
down-side to using a scope probe is that you'll end up with a 10X
signal attenuation which can make for a pretty short square wave on
the higher ranges. The normalizers had a 2X attenuation factor to
minimize that effect. So, the 10X probe method will work great, but
there will be that one small down-side. By the way, 15pF is about as
small as the input capacitance runs. I think the only smaller
normalizer that Tek made was 12pF. For the most part, Tek and most
other manufacturers settled on 20pF as the input capacitance
of "choice".

There was a foolish push at one time for Tek Service Centers to use
Type 30 L/C meters to calibrate their normalizers to their marked
value so that every scope could be adjusted to their marked value.
The proved to be a time-consuming move and rather pointless as few
customers ever moved a probe farther than one channel away from where
it started (let alone to another scope which might have a huge
difference in input capacitance anyway. The input capacitance
adjustment of most of the scopes was usually a thin brass screw in a
cylinder of Teflon and had an adjustment range of maybe 1-2 pF at the
most, if that. The only thing we ever tried to do was to match the
input C of all channels on a scope or plug-in and then compensate the
attenuator. Technicians should be checking their probe compensation
on a regular basis and not depend upon all scopes in the lab or shop
to be normalized to each other so that probes never need to be
checked. That would be a bad habit to develop.

By the way, if you end up working on a lot of scopes, rather than
buying several normalizers, you can get just one normalizer and
change out the capacitors by getting rid of the fixed and variable
parts and just installing one with a larger range and the right
physical size that'll go from maybe 10 to 50pF. It'll make it a
little harder to adjust, but won't be that bad and will work for any
input capacitance you'll come across.

Dean



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