17 Dec
2008
17 Dec
'08
11:33 a.m.
On 17 Dec 2008 at 13:59, Paul Koning wrote:
Before that came out you'd need something else,
and a Weston cell is
certainly a very good way to solve the problem.
Except that you can't draw much current from a Weston cell. When
used as a reference in a potentiometer, for example, you must first
adjust the output of a dry cell to match the standard cell--and then
use that dry-cell voltage as the bridge reference. Chart recorders
would periodically recalibrate their reference automatically, but
with manual equipment it was a real bother--and the temptation to
skip the step was strong.
The contents of a Weston cell read like an advertisement for a hazmat
cleanup service--cadmium and mercury.
Cheers,
Chuck