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
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