A crystal oscillator is a device used to transform electrical energy into or produce it from mechanical energy. In most cases, these oscillators are subjected to an electrical impulse which causes them to oscillate at a precise frequency. The frequency of each crystal remains stable at a variety of temperatures and pressures and in the presence of many different materials and chemicals, making it ideal for operations that require precise timing under many circumstances. These devices are commonly used in watches and electronics both for their precision and durability.
The properties of the crystal oscillator were first discovered in 1880 by Pierre and Jacques Curie. These two scientists discovered that quartz crystals will produce an electrical charge when forced out of shape and will change their physical shape when subjected to an electrical charge, a property they named the piezoelectric effect. Experiments with these crystals showed that they oscillated at a precise frequency when electrical current was passed through them.
One of the main components of a crystal oscillator is the crystal itself. Many different types of crystals can be used as oscillators, but the most commonly used variety is the quartz, which is often grown under controlled circumstances before it is cut and used as an oscillator. The crystal is cut into a thin slice or into the shape of a tuning fork and then placed between two conductive metal plates. When current is passed through the device, the crystal begins to expand and contract, or oscillate, at a precise frequency. An amplifier connected to the crystal oscillator increases the output of the device which can then be used to time mechanical or electrical processes.
The stability of the frequency of a crystal oscillator makes it ideal for use in watches and electronics. Quartz crystal has been used to control the timing of watches since soon after the discovery of the piezoelectric effect. Watches with these oscillators are known for their ability to withstand temperature and pressure changes and to remain accurate for long periods of time.
In electronics, crystal oscillators are often used in computers, cellular phones, and radios. The crystals are useful in these devices because of the precision of their oscillation, which allows the crystal to be used to filter out unwanted frequencies. The crystal oscillator also expands and contracts mainly along one axis, which gives the device a low phase shift. These two qualities give it the ability to time a process accurately and to maintain a strong signal, both qualities that make it ideal for use in electronics.