Hi You need to extract Cm, Lm and Rm ( motional resistance, capacitance, inductance) for the mode you are looking at. You also need C0. Once you have those you can come up with Q. Because of the interaction between C0 and the other parameters, you need to extract them all. ( yes, you could extract Fs and leave out Lm, it’s still three parameters plus C0).
Bob > On Mar 6, 2021, at 4:02 PM, Dan Kemppainen <[email protected]> wrote: > > Hi All, > > Just to be clear, I am not the person who made the crystals glow blue. I just > noticed some pictures of that happening on the auction site: > > https://www.ebay.com/itm/8x-Quartz-Resonator-1000-kHz-Crystal-oscillator-gold-Sonoluminescence-effect-NOS/113862454353 > > https://www.ebay.com/itm/1x-Quartz-Resonator-1000-kHz-Crystal-oscillator-gold-Sonoluminescence-effect/113874435589 > > I certainly will not abuse these crystals this way! > > > > As for measurements, I'm trying to take some measurements with the equipment > on hand. Currently, that is an Agilent 33220A signal generator, and TDS3000B > oscilloscope + Active FET Probe. > > Years ago I put together a little Excel Macro program that sweeps the signal > generator through a range of frequencies, and measures the voltage and phase > of the signals on the oscilloscope. Basically, the sampled signals are run > through a sine fit routine, which gives very good estimation of sine > amplitude and phase shift (With frequency being set by the signal generator). > > Using this setup, the first try involved making a voltage divider with a > fixed resistor and the crystal. The signal generator was used to drive signal > into the resistor, through the crystal to ground. A standard 10x probe > monitored the signal generator voltage, and the FET probe in series with a 1K > resistor (for more isolation) was used to monitor the crystal voltage. (The > probes were compared before the test, and channel skew adjusted to zero). > > Basically, this is a voltage divider made with a resistor and a crystal. From > this, a frequency response curve was generated. See attached image. > The -3dB and +/-45 deg phase shift points match well. They are also quite > close to the Fs frequency (999,999.800 Hz). Those -3dB points come out to be > 999,990.640 Hz and 999,990.910Hz. > > However, I'm a bit concerned that the Q calculated with these numbers is a > bit higher than expected based on what I've read. Running the test with a > smaller series resistor (100 Ohm) results in a lower Q (As would be expected > as the 'load' on the crystal is higher), although even these numbers are > quite high. > > In order to try to measure Rs, the voltages of the divider were measured at > Fs, and RS was calculated accordingly (Easy calculation, as phase shift = 0 > deg). This was repeated with several series resistor values (10, 100, and > 1000 Ohm). These tests resulted in Rs = between 4 to 7 ohms (depending on the > series resistor). > > My concern is, are there any potential pitfalls in this measurement setup? Is > there something that will give more accurate results, given the equipment on > hand? Certainly the Q value seems unreasonably high, and Rs seems quite low. > However, these are large low frequency resonators (being 25mm in dia.). > > > Thanks, > Dan > > > On 3/6/2021 12:00 PM, [email protected] wrote: >> Message: 4 >> Date: Fri, 5 Mar 2021 16:03:51 -0600 >> From: Dana Whitlow<[email protected]> >> To: Discussion of precise time and frequency measurement >> <[email protected]> >> Subject: Re: [time-nuts] Old Crystal. >> Message-ID: >> <CADHrwpcb3_9xeeCHg3r30DS7oGq-CKsXYjW4XM=q=dt0gv5...@mail.gmail.com> >> Content-Type: text/plain; charset="UTF-8" >> Blue LEDs under Nixie tubes might have a deeper purpose than appearance- >> they can also >> help the Nixie tubes get started upon turn-on (especially if they're >> getting old). I once stayed >> in a hotel room whose light switches had neon indicators to help one find >> them in the dark, >> and the one near the entrance door was getting awfully marginal. I >> happened to have a blue >> LED penlight with me, and I found that shining that on the switch face made >> a radical >> improvement in making the neon indicator keep going, even at a range of > >> 20 feet. And >> this flashlight was no powerhouse either- it was a single LED with no >> auxiliary focussing >> optics. >> Dana > <457 Sweep 1K Series.jpg>_______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
