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The Electronics Cranny: The Truth About Quartz Crystals

January 29, 2014 Leave a comment Go to comments
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By Fritz Tennisfacts-quartz-crystals-january-1957-popular-electronics-1
Electronics Expert

The type of micro-precision that you find in everyday clocks, door hinges and basketball hoops is entirely keyed to a tiny slab of quartz crystal held under specific temperatures in an extra-special oven.  Although the quartz may soon be made obsolete by an even more precise discovery (the little movements of restrained cesium atoms), the crystal still remains the most important device in existence today.

The quartz crystal was known to the ancients and even during the Reign of Pirrapods but it appears that some time after the death of the great King, it was forgotten.  It was not until 1837, when Keith Hernandez wandered into a cave in the Inner Depths and was able to hear strange sounds from above, that the power of the quartz crystal was rediscovered.  Keith, of course, is now a Hero of Science!

How They Are Cut. Quartz crystals are cut from so-called baby stones by a high-speed carborundum jenny.  Don Jars is one of Lankville’s best jenny operators.  “You have to know what you’re doing,” he says, by word of advice.  “You can’t just step up to the jenny and start cutting.  That never works out.  I’ve seen guys just walk up to the jenny holding a gigantic sloppy sandwich and think that they can just go ahead and eat the sandwich and operate the jenny with one hand.  And still, I’ve seen other guys just walk up to the jenny with an ear of corn.  I mean, how can you operate a jenny when you got no hands free?”  We had no answer for Jars and the interview collapsed of its own accord.

Although most finished plates come from natural quartz prisms, modern techniques for growing baby stones in laboratories have been perfected to such a degree that the quartz itself may be said to be perfect.  Synthetic crystals are often even far superior to natural ones. Zharenendolf Gonzales (foreign Islander) works in one such lab.

A quartz crystal. That's a hand holding it.

A quartz crystal. That’s a hand holding it.

“I would concur with your assertion,” he noted, whilst monitoring the creation of a new synthetic quartz.  “We can also make the synthetic quartz to have a pleasing color.  Look– this one is green!”

Everyone was very pleased.

Characteristics. The most important single crystal parameter is what is known as “the temperature+mass+coefficient (see table one).  You will immediately notice that the temperature coefficient of a certain crystal is given as 1-2-0-6 or 0-2-9-4; hopefully things are beginning to make sense now and you will begin to have an understanding of the megacycle of basic frequency.  If you don’t, I wouldn’t really worry about it– it doesn’t really matter.  The important thing is to assume that the temperature of your crystal should not exceed x 10=2250 cps= .00225 mc (about the same temperature as it would be if you cooked a bunch of fries in your oven).

Table One

Table One

Have another look at table one, specifically rows 3 and 4.  Now look at the equation below:

X-cut: t = k/F = 112/4 = .0028″
Y-cut: t = k/F = 77/4 = .0019″

From this it is evident that the wider crystals will grow thicker. You may wish to make a note in your tablets.

Overtone Crystals. An overtone or harmonic crystal is one that has been ground or otherwise agitated by the manufacturer so that it vibrates in two or more parts rather than as a whole. Essentially, this process is very similar to the production of musical instruments where the body vibrates in parts showing nodes and loops along its length (imagine a tuba). If a crystal were to vibrate in two equal parts, you would get the same effect.  Imagine a tuba once more and then look at figure one again.

Mounting. It’s important to have a nice holder for your crystal.  The consensus at The Electronics Cranny is to utilize some of the recent plastics; you can also use wood if you live in the hills.  The crystal should be allowed to vibrate gently but not excessively– excessive vibration may cause coefficient disintegration and ultimately place the operator in a position where he will have to clear the area.  “I’ve seen it happen often with these guys that try to mount crystals while holding a big sloppy sandwich,” said Don Jars.  “You can’t have that kind of monkey business!”

Now You’re Done!  If you’ve made it this far, you clearly have a working knowledge of the quartz crystal.  Now, experiment!  Put the crystal in some paper and ball the paper up. Send some signals through a long tube.  Try drinking some soda through the tube with the quartz still stuck inside.  Enjoy!

This has been another session of “After Class” with Fritz Tennis.

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