subject: What Is A Quartz Crystal [print this page] To start with some background information, quartz crystals in electric systems are crystals of quartz, sliced in a particular fashion to create an electronic signal at a consistent frequency that may be used to stabilise the frequency of oscillators and timing signal generators.
They can be produced by specialized electronics companies to precise specifications including size, form, frequencies, temperature tolerance and robustness.
Even though quartz is not conductive (meaning it doesn't carry electricity like many metals such as copper), it has certain electrical properties that make it very useful for particular electronics. Specifically, it is piezoelectric. "Piezoelectricity" is a word derived from the Greek word "piez" or "piezein", meaning "to press"; Piezoelectric substances are non-conductive components which generate electricity when you subject them to pressure, and vice-versa: They experience physical alteration when you run electricity through them.
The electrical charge generated by the crystals can them be used in electrical circuits.
The exactness of quartz crystals helps make them extremely beneficial to modern electronics; Having said that, quartz present in the natural world is not generally pure enough to be beneficial in a exact electric circuit, so man made quartz is usually used in today's manufacturing world. Once the quartz crystal is cut into a bar or disc shape, it has two electrical leads connected to it and the whole crystal is plated with some protective metal coating. The resulting metal-coated-crystal with 2 pins sticking out of it is the common crystal of the electronics world. The crystal is rated for a certain frequency, which is basically how quickly it vibrates when you pass electricity through it; The frequency of a crystal is mainly affected by how thick it is, and so crystals of widely varying frequencies can be achieved just by cutting them to a certain thickness.
Once you have this production crystal, though, it doesn't generate a perfect, regular oscillation by itself, even after you pass an electrical current through it; The crystal must obtain its own frequency to maintain vibrating. This is because the crystal functions as a filter. (A filter is an electrical resource that permits certain frequencies to pass, and blocks others.) So once you start the crystal oscillating with an initial jolt of electricity, the output of the crystal needs to actually be fed back into itself, generating a feedback loop that keeps the crystal vibrating. Thus the crystal's output must have a minimum of two connections, one through a channel that feeds it back into the crystal, and another that amplifies the output for use in the actual application that needed the frequency in the first place.
All crystals can be used in series-resonant or parallel-resonant mode. These 2 modes produce two frequencies from the crystal that are slightly different, but only slightly. Often, a crystal is classified as being serial- or parallel-resonant, which means it will operate at its rated frequency in that mode; However, you can operate it in the other mode as well, you just will get a slightly different frequency.
There are in excess of two billion quartz crystals fabricatedannually and the majority are integrated into devices such as wrist watches, time pieces, radios, computers, mobile phones and smart phones. Quartz crystal Oscillators are furthermore found inside electronic verification, measurement and monitoring devices throughout many industry sectors.
Examples of these instruments include electronic counters, signal generators, and oscilloscopes.
