DORAN potentiometer and millivolt source. Extremely good "almost as new" condition and believed to be 100% working - except that the standard cell is low in voltage (giving only 0.8 volt). The galvanometer is working perfectly - the Weston cell has enough power left to give a 100% deflection in the standardisation mode. Needs two 1.5 volt batteries to function, these were originally type R1662 (Ever Ready) with screw on connections but any 1.5 volt zinc-carbon or similar cell would do. The standard cell which gave the stable reference voltage is a Weston type. No doubt these are still available. They last around 30 years and were used as a voltage reference before the days of Zener diodes. I used to know how to use this instrument - its pretty basic stuff but I don't have a full instruction book. Anyone with a serious interest in it will either know or easily be able to find out how to use it!

The instrument functions both as a millivolt source (ranges 20, 50, 100 mV) and as a thermocouple (or general use) potentiometer reading FSD from 0 to 20 milivolts with a x5 range which probably enables 100 millivolt to be measured. Resolution is 0.01mV, or 10 microvolts. Obviously whilst this could still be used it is more of a collectors item. It is in 'almost as new' condition with a bit of dust being the only apparent imperfection. Deserves to be cherished and maybe displayed somewhere.

A selection of photos follow. It has been kept in a warm dry domestic cupboard for over 30 years and now needs a new home. Weighs about 5 kilogram. Will post worldwide but it will cost appropriate amount with good packaging and insurance.

In the photo above, the Weston Standard cell is the black rectangular object in the bottom left. Ever Ready 1.5 volt R1662 cells were originally fitted into the clips at top left and top right (on the side).

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