Real time monitoring of the objective is a good way to go. I don't thing making semiconductor or mirors is as critical, hence a chamber monitor suffices.
-John ========== > One of my side jobs is to produce better than state of the art ultrasound > transducers. That being said, there is nothing particularly better about > mine other than when I say it's a 1MHz transducer, I really mean > 1.00000Mhz, > not 980kHz, not 1.2Mhz. The way I achieve this is to lay down gold, a few > atoms at a time, and track a resonance peak (network analyzer and some > simple code in VB of all things). We actually drive the transducer as we > sputter coat the gold on top and can see the resonance point shift, real > time. Cool stuff. They use a similar process in industry but they're > looking at one data point in a vacuum chamber full of transducers. I'm > looking at every single one. > > -Bob > > On Sat, Aug 15, 2009 at 1:56 PM, J. Forster <[email protected]> wrote: > >> > And billions of accelerometers (from air bag sensors to Wii game >> > controllers to the iPod touch and iPhone) have been produced in >> > the past decade. Google words like MEMS Quartz Accelerometer. >> > Also for Quartz Rate Sensor QRS. >> >> I'm not so sure they use quartz. The ones I've seen are micromachined >> from >> silicon and have both the beam and electronics on the same chip. >> >> > I've seen quartz resonators used to measure to impurities in the >> > making of semiconductor wafers -- they measure the change in >> > frequency of an exposed quartz resonator as atoms fall on the >> > exposed crystal and change its frequency. Note that a 1 mm >> > quartz crystal is only about a million molecules thick. So adding >> > a layer of only 1 atom will change the frequency in the ppm range. >> > We can measure a thousand or million times better than that. >> >> Not impurities, but the deposition of metalizing films, etc. >> >> > As you feel your heart beat, google for Quartz Pressure Sensor >> >> Again, I think these are semiconductor sensors. >> >> > Quartz is really quite amazing. It's almost a shame to shield it >> > from everything so all they have left to do is try to measure time! >> >> LoL. The crystals ARE pretty nice. >> >> Best, >> -John >> > >> > One other note: rubidium vapor frequency standards are much >> > more sensitive to magnetic fields than cesium beam standards. >> > I've heard that military sub-hunting sea planes use deliberately >> > un-shielded rubidium clocks to detect hidden submarines. Google >> > for words like Rubidium Magnetometer ASW P-3 Zeeman >> > >> > As always, one man's error is another man's signal... >> > >> > /tvb >> > http://www.LeapSecond.com >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
