Joseph Gwinn wrote:
I'm interested in the electronic levels mentioned in the thread "Surface
plate maintenance (19 March 2009 et seq), specifically the Talyval from
Taylor Hobson. This is the Mahr unit. I've been trying to find the
original patents (long expired), but have struck out, probably because
the US Patent Office only has searchable text back to 1976. I think it
was Jon Elson who mentioned these patents.

Only thing I know is that the original Talyvel was made in the early
1960's, to guess from the appearace of the unit.

But, the technology is not real complex. You need a pair of opposed,
well-matched proximity sensors that are not subject to differential
drift. You suspend a very light platform from insanely tiny wires. I
suspect it has an aluminum vane that hangs between magnets for damping.
The display box reads the difference between the two sensors. Now that
I've seen the inside of one, I'll bet I could make one myself that would
actually work. Of course, making it work as WELL as the Talyvel, even
under various slants on the cross-axis, is not so easy.

Jon