Bruce Griffiths <[EMAIL PROTECTED]> wrote: > Max
> A capacitance bridge using a transformer would be a lot more > stable than merely using the capacitance to vary the frequency of > an LC oscillator. > The advantage of a capacitive sensing technique over a light beam > is that it has much simpler and potentially more stable mechanical > system than when a the mercury colum interrupts a light beam. > Unless of course on has the Mercury column move a moire grating or > similar setup such as making the top of the mercury column a > reflector in an interferometer system. > Bruce Very clever! According to this web page, interferometry could give a resolution of 0.15 nm, or close to the radius of a silver atom: http://www.aerotech.com/products/engref/intexe.html This video shows the basic principle in case you want to make your own: http://www.metacafe.com/watch/1381543/laser_interferometer_homemade_for_20/ You can see from the movement of the fringes how sensitive interferometry can be. This should give unprecedented temperature control, so maybe someone has already done it. A google search gives lots of hits, but it is difficult to distinguish between controlling the termperature of something, and the need for accurate control of temperature to get stable fringes! Great idea! Regards, Mike Monett _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.