[GreenKeys] What is this?

[Roy Morgan]

On Aug 22, 2013, at 9:27 PM, Lester Veenstra <Lester at veenstras.com> wrote:

> Resistance standard

As Couryhouse mentioned:

That thing is a selectable resistance device of ancient times meant for use as a wheatstone (or other) bridge.  The Guitar-Tuning-Peg-Like things make the connections in tight fitting holes - provide very low resistance contacts (If clean).  

Appears to have binding posts for galvanometer (to detect a null) a battery, and the unknown.  The resistances seem to be arranged to  provide a multiplier leg and two or three other legs of a bridge circuit.

My guess is that it dates from the early 1900's.  I would expect the thing to have held its accuracy well. (I have two perhaps contemporary rotary switch decade boxes made in Germany - they have surprisingly accurate steps - all made of lacquered brass and ebony-like knobs in furniture wood cases.)

Some similar devices had provision for a water or oil bath to surround the resistance elements for temperature control leading to increased accuracy.

A true artifact of days long gone by.

Roy

Roy Morgan
k1lky at earthlink.net
K1LKY Since 1958 - Keep 'em Glowing!