Hello Dave. So far I have identified 3 different Leeds & Northrup "Boxes". Originally my intention was to re-purpose the box, panel connectors and switch for a project to make my own precision resistor banks.
All use different switches and vastly different resistors to achieve their original purpose. The subject of the first one is the "Ayrton (wired) Shunt Box". It was used with a galvanometer as a sort of attenuator (current divider), uniquely wired in the Ayrton fashion to insure the galvanometer was always connected to a shunt resistor, even during switching. Think of the scheme as a stepped potentiometer, the meter was between the two extremes, while the source went to the wiper. Just backwards from a Voltage divider. Next is the "Shunt Box". It's resistors are copper straps, the lowest value is made from a copper sheet maybe 5 inches wide, bent into a corrugated shape to fit inside the box. Remarkable construction, should be quite stable as a milliOhm standard. The last one is called "Volt Box". Its resistors are wire wound on ceramic forms, obviously with great care. The switch is protected and possibly gold plated contacts. Multiple series connected resistors are used to provide the correct values plus spread the current (heat load) around, and they are spaced far apart and with air space around each one. So far no clue as to its original function but of course I have traced the schematic. Very little is freely available on the 'net about them nor a period catalog so far. George Dowell _______________________________________________ volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
