On Sun, 17 Aug 2003 00:18:41 GMT Robert Baer
wrote:

Jim Adney wrote:

Now I've got an old Eppley standard cell sitting across the room, and
those could be held to a microvolt, but they DID age, and they DID
have a temp dependence. None of that affected the first 4 digits,
however. Those last 3 digits are a LOT tougher. ;-)

Ahhhh..... you speak of differences of primary and secondary
standards.

In the case of the battery I was just thinking of this as a useful
reference, especially since the OP didn't specify any particular
tolerance.

The Eppley cell is probably a secondary standard at best. In this
context, I don't think I would be willing to call the carbon-zinc cell
even a tertiary standard.

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Jim Adney
Madison, WI 53711 USA
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