
The Weston Standard Cell (2011) - segfaultbuserr
https://www.conradhoffman.com/stdcell.htm
======
analog31
I've got one. It's in an ancient Leeds and Northrup potentiometer that was
made for reading a thermocouple.

You use the cell in two stages. First, you adjust a conventional variable
voltage source until it equals the Weston cell. Then you leave the Weston cell
alone and use the variable source for subsequent input voltage measurements.
That way, you maximize the lifetime of the Weston cell.

As for the potentiometer, it's a precise resistive voltage divider. You dial a
voltage until it equals the input voltage, then read the position of the dial
on a scale. That's your measurement. This application is also where
"potentiometer" gets its name.

The indicator for when two voltages are equal, is a super sensitive
galvanometer. You push a button to make a measurement, seeing if the needle
moves to the left or right. So the Weston cell is actually only doing anything
for a split second. The whole thing contains no active electronics.

All I've done with it is to make one thermocouple measurement, and to very
briefly test the cell with my digital voltmeter.

~~~
opwieurposiu
The switches and knobs on that old testgear are so satisfying to use. Clunk
Clunk, POP!. I have a Leeds and Northrup bridge and some decade resistors and
they are still 0.01% accurate after 80 years!

~~~
analog31
I love the mahogany boxes too. Sadly, mine is newer and has a painted steel
box.

I'm thinking of replacing the Weston cell with a solid state voltage reference
so I can dispose of the cell but keep the instrument.

------
mzs
more info including photos and how they were used to accurately measure
voltages:
[https://entertaininghacks.wordpress.com/2016/12/28/a-weston-...](https://entertaininghacks.wordpress.com/2016/12/28/a-weston-
standard-cell-an-introduction-to-voltnuttery/)

