Hi Bob, Why do they have to be so precise ? And what are they being used for ?
Bill....WB6BNQ Robert Darlington wrote: > 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 <j...@quik.com> 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 -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > 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. _______________________________________________ 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.
