Buck Frobisher wrote:
"Sjouke Burry" wrote in message
...
The book is from 1958

You learn something new every day. I had never heard of these. Can anyone
elaborate a bit on what exactly they were used in? Calibrating what,
meters?


Anyplace/time you needed an accurate voltage.
In the lab you had very accurate resistor divider banks,
where you reduced your test-voltage to the same voltage
as the cell.
That was tested with a very sensitive galvanometer,
where, when the galvanometer indicated zero (micro)volt
difference between the two, your testvoltage followed
From: Vtest=bankratio X cellvoltage.
In this way, at the moment of the readout, the cell did
not supply any current, and thus the error was minimal.

And yes, meter calibration,reference source calibration
(current and voltage) were ever needed.
And even to calibrate these reference cells, because due to
impurities non of these cells had exactly the same voltage.
Now, how to calibrate the first one? I have no idea, but in
most countries you had a standards lab to do that for you.