WAS Re: [time-nuts] Restoring GR 1120-AB Frequency Standard Mike,
I fail to see how you would apply the laser interferometer system to the measurement of temperature. At least as a viable means of temperature control to any reasonable degree. At the Navy's Primary Standards Lab, here in San Diego, there is a very complete laser interferometer measurement system. It is housed in its own room that is "completely" controlled for environmental conditions, i.e., temperature, humidity, air filtration, etc. The actual laser platform is a huge, highly machined micro-flat granite table of considerable weight mounted to a fine grain concrete pillar that goes down to the bedrock, some 30 feet below, and is completely separate from the rest of the building's foundation. When the operator enters this laser room, it takes a little over 30 minutes for his body heat to be stabilized into the matrix of the rooms environment before any real measurements can be made. Even though this granite table is, like in the neighborhood of, around 2000 lb., laying a standard U.S. Navy glass coffee cup (empty) on the very, very corner of the granite will deform the light beam quite visually. My reason for the above description is to point out the scale of the installation, the sensitivities and the problematic issues one would have in trying to control temperature sans everything else changing. I suppose it can be reduced in size, but then doing so also reduces the sensitivity of the system. Did I mention that the granite table is 3 feet square ? That allows for folded beams to increase the length for the needed sensitivity. Now equate all of the above to a small oven in an instrument. Not likely possible. Bill....WB6BNQ Mike Monett wrote: 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: [1]http://www.aerotech.com/products/engref/intexe.html This video shows the basic principle in case you want to make your own: [2]http://www.metacafe.com/watch/1381543/laser_interferometer_homema de_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 [3]https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. References 1. http://www.aerotech.com/products/engref/intexe.html 2. http://www.metacafe.com/watch/1381543/laser_interferometer_homemade_for_20/ 3. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts _______________________________________________ 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.