[volt-nuts] Which meter?

[WB6BNQ]

Greg Burnett wrote:

> Hi Bram,
>
> << snip >>
>
> I think you might find the 3458A's linearity to be typically < 0.06ppm on
> its 10Vdc range. (Fluke's 720A Kelvin Varley Divider isn't linear enough to
> verify this, so you'd need a JJ-Array to "prove" it.)
>

Greg,

You got to be kidding me !  Those numbers (and others) you quote are after a hell
of lot of statistical manipulation in a very highly controlled environment.  In
the "FIELD," which covers just about everything and everyone else you would not
be able to prove it no matter how hard you tried.  Besides, unless you are just
trying to play the specmenship game, there is absolutely no requirement for such
numbers you quoted.

On the practical side, and being quite honest, there is no need for such extreme
linearity as the original poster needed to study the stability, as linearity was
not mentioned for the job at hand.  Once you have a referenced null condition it
is a matter of recording the variation from that point.

If you use the right equipment and apply that equipment properly, his current DVM
is way more then he really needs.  Its more a matter of understanding the
systemic issues and accounting for them correctly.

Unless he is paying for the factory to select the very best from a hugh run of
LTZ1000's, then he is not going to do better then Fluke's voltage references
which would be at least 5 times better then he is going to achieve.  Fluke has
either paid for the best or are buying a hugh quantity and doing their own
selection.  I doubt the poster has the ability to do better.

So why try to reinvent the wheel ?  Use specifically selected pieces of Fluke
equipment that can do the job right and learn how to properly use it.  Being able
to repeat your measurement process is way more important then playing the number
game.  Unless you are just looking for a way to justify buying a new piece of
equipment, then all honesty is tossed out the window.

Bill....WB6BNQ