G. Doughty wrote:

Good Morning,

I am putting together a winkey keyer kit (I know it is not true homebrew,
but I am just a lowly English teacher). Anyways, I have a variable pot with
three poles and need to know which one is ground. How can I find that out
with a multimeter?

Thanks and 73
G. Doughty
ki4bbl AT cox DOT net


Ditto all the comments already made (except that you probably want to
ground one of the ends rather than the wiper), plus: A potentiometer is
nothing more than a strip of resistive material with terminals at each
end and a movable contact attached to the knob somewhere in the middle.
The movable contact is called the "wiper" because, well, it wipes.

If you ignore audio taper pots the resistance between any two points
along the length of the strip is proportional to the distance between
the points. So if you have a 2" long strip in a 20k-ohm pot, and you
place the wiper 1/2 inch away from one end, you'll see 5k-ohms between
the wiper and that end (and 15k-ohms between the wiper and the other end).

Potentiometers almost always come with three leads, and the leads are
almost always arranged so that the middle lead is the wiper -- the only
exception I know is with some precision multi-turn pots, but you can
ignore those. The drawing below shows the correspondence between a
schematic drawing of a pot (euro-style, kinda -- just take the box to be
the usual squiggly line) and a drawing of a panel-mount pot.


Schematic
symbol
(euro-style) Physical
drawing
End1 (poor)
|
.-.
| |-- Wiper
| | / \ - End1
'-' | O |- Wiper
| \ / - End2
End2
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de


--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com