David Nebenzahl wrote:

I have an old galvanometer (nice Weston in a slant-front black crackle
case). Its scale reads 30-0-30. What units are these? Or are they just
relative values for comparison?



When you said 'galvanometer', I immediately expected you to be talking
about a 'mirror galvanometer': a large sensitive laboratory instrument
rather than an ordinary moving coil meter, which of course is
also a 'galvanometer' but is not commonly (at least in the US) labeled
as such.

Michael