I used to produce ultrasound transducers using a very similar method. I'd continuously monitor the resonant frequency with a network analyzer as I'd lay down gold/silver/whatever with an evaporator cup from both sides. My chamber has a shutter to cover the transducers (I think it has 12 or 15 stations around the circumference), but I could vary the current through the tungsten heaters on a per transducer basis to taper off and stop the deposition.
Every once in a while a customer wanted a 10.0000ish MHz transducer, and all Panametrics (Olympus NDT) could crank out would be something kinda sorta near 10MHz -like 9.85MHz. As a lowly technician and not a scientist, I don't understand why this mattered for the work they were doing, but the national lab here in Los Alamos really seemed to like their matched, high precision transducers. -Bob On Thu, Jun 20, 2013 at 5:57 PM, Gary <n...@lazygranch.com> wrote: > A common scheme in metal deposition measurement is to measure the > frequency of a crystal prior to starting the deposition process, then > monitoring the frequency shift of the crystal as the metal is sputtered. > > I was told crystals are tuned this way at the factory, but don't know this > for a fact. > > "Burt I. Weiner" <b...@att.net> wrote: > > >Brian, > > > >I remember grinding FT-243 crystals. I had a TV set safety glass > >about 18" square and about 1/4" thick. That and some Comet type > >cleanser mixed with water to make a thin paste would work wonders. I > >was taught to put my finger on the corners and grind an equal amount > >on the 8 corners (4 on each side) so as not to remove the bevel of > >the quartz. Once I applied this lesson I was able to grind crystals > >that were more stable and more active. When I over-leaded them I was > >generally able to remove the lead using alcohol. I've still got the > >old TV safety glass although it has an area near one corner that is > >very opaque do to all the grinding that was done in that area. Those > >were fun days! > > > >Burt, K6OQK > > > > > >>From: Brian Alsop <als...@nc.rr.com> > >> > >>Reminds me of the FT-243 xtal controlled transmitter Novice days. > >Xtals > >>of the frequency you wanted were hard to come by. We would grind > >xtals > >>a bit on a bed of very fine abrasive to raise their frequency. > >> > >>The other trick was taking a pencil and adding graphite to the xtal > >>faces to lower it's frequency. You couldn't add too much or it would > >>stop oscillating-- forever. Never did understand the forever part. > >>Removing the graphite didn't bring it back to life. > >> > >>Brian > >>K3KO > > > >Burt I. Weiner Associates > >Broadcast Technical Services > >Glendale, California U.S.A. > >b...@att.net > >www.biwa.cc > >K6OQK > > > >_______________________________________________ > >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. > > -- > Sent from my Android device with K-9 Mail. Please excuse my brevity. > _______________________________________________ > 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.