On Thu, 27 Aug 2009 13:29:43 +1000, Sylvia Else
put finger to keyboard and composed:

Jeff Liebermann wrote:
On Thu, 27 Aug 2009 12:09:15 +1000, Sylvia Else
wrote:

Ummm... thanks for not calling it a rheostat.
Why on Earth would I do that?

Because it really is a rheostat. Officially, if there are three wires
involved, it a potentiometer. If there are only two, it's rheostat.

It has three. Five volts on side. Zero on the other. Middling in the
middle. This presumably reduces its sensitivity to track wear.

Yamaha's YC-45D and YC-25D combo organs use optical sensors -- two
wires for a 14V bulb, and two for a CdS photocell. Strictly speaking,
you should measure the resistance of your pot, in the absence of
power, to be sure that your device is not some fancy optical gadget
that is simulating a mechanical pot. But it does sound like it may be
the latter, and for $25 you would probably only want to treat this as
an academic exercise to satisfy your curiosity.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.