A Vintage Moisture Meter - The Protimeter

[Yorkie]

Interesting instrument Al - I noted that the instruction sheet was written not too long ago in 1977 by Professor T A Oxley of Protimeter Marlow, Bucks, so out of curiousity I googled the Prof and Protimeter and noted that the second edition of a book that he co-authored was published in Nov 2013 by E G Gobert, E G and T A Oxley entitled 'Dampness in Buildings - diagnosis, treatment, Instruments':

http://www.amazon.co.uk/Dampness-Buildin...0750620595

Also Protimeter seems to still be in business employing 25 people in Marlow, but is now G.E.Protimeter and as we might expect, the instruments are rather more sophisticated:

http://www.ge-mcs.com/en/

As to the lithium cells, I noted at the Antique Radios link that Paul provided, one of the posts states:

I see outfits offering the Exell 413 battery they spec it at 110mAh, (milliAmp hours). For rough comparison the lithium coin cells are rated from:

CR2016 = 90mAh
CR2025 = 163mAh
CR2032 = 240mAh

So ten 2032s would seem to be the best bet capacity wise, but of course, they won't fit!

The problem with the 1225s that you suggest, which will fit (12mm diam x 2.5mm thick). is that they're only 50mAh

http://en.wikipedia.org/wiki/List_of_battery_sizes

Incidentally, the numbers denote the diameter and thickness of the cells - nothing more, so for example 2016 is 20mm diam x 1.6mm thick, 2025 is 20mm x 2.5mm thick, and 2032 is 20mm x 3.2mm thick, and 1225 = 12mm diam x 2.5mm thick. (Maybe you already knew that).

Have fun!