! On 2012-10-11, at 9:47 AM, Brendan Gillatt w= rote: > On 11 October 2012 00:27, M.L. wrote: >> A while back there was discussion of non-volatile displays. I found >> one that nobody thought of: >> The Mercury Coulometer >>=20 >> An obscure, antique, highly toxic device that has a glass tube, two >> electrodes, and two columns of mercury separated by a liquid >> electrolyte. >> Electrical current passing through the device transfers mercury from >> one side of the electrolyte bubble to the other, creating a linear >> indicator - albeit very very slow, fragile, toxic, etc. >>=20 >> See the diagram at the end of this paper for a clearer picture: >> http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19700023619_1970023= 619.pdf >>=20 >=20 > I actually own one of those devices! It is packaged in a form similar > to a large, glass bodied fuse with wires soldered to both ends. A > graduated paper scale sits behind the mercury column to mark time > intervals. Until now I've not known the name of the device, let alone > how to drive it. I've got one as well, in an old (1970's) Tek dual-beam storage oscilloscope= ! Something like 0-5000 hours. --sp --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .