Just as a quartz crystal unit has temperature characteristics, an oscillation circuit has faint temperature characteristics. SPXO is the simplest oscillator produced by integrating a quartz crystal unit and an oscillation circuit. In a circuit, a quartz crystal unit usually functions as an oscillating element, although it is sometimes used as a filter or a sensor. (Note: "X'tal" is an abbreviation of Crystal.) SPXO (Simple Packaged X'tal Oscillator) The crystal oscillator is classified in several types depending on the function. Processing technologies of these units are broadly classified into two types: The mechanically processing method and the chemically processing method.Įach vibration mode has a different frequency range and electrical performance, and therefore appropriate vibration mode should be used depending on the module. For example, the frequency of a thickness shear mode resonator (AT cut, BT cut), a tuning fork type quartz crystal resonator and contour shear mode resonator (CT cut, DT cut) is decided by the thickness, the length and width of the tuning fork and the length of one side of the square, respectively. As for frequency, the parameter to determine frequency is different depending on the vibration mode. The quartz crystal unit has various vibration modes according to the crystallinity and piezoelectricity, and some of them have the zero temperature coefficient. Cutting orientation of quartz crystal element, frequency, vibration mode Moreover, quartz crystal units are widely used as a source of standard clock for wrist watches, stopwatches or the like. Owing to this excellent frequency stability, quartz crystal units are used for communication devices such as cell phones and wireless applications as well as consumer devices such as televisions, video recorders, digital cameras and computers, to provide accurate reference signals for processing a huge volume of information simultaneously and quickly. Moreover, quartz crystal units are extremely stable both physically and chemically, and therefore the frequency change after aging is extremely small. Quartz crystal units, such as AT cut and GT cut crystal units, have zero temperature coefficient over a broad temperature range with room temperature at the center, and therefore have excellent frequency-temperature characteristics. To cite physical properties, quartz crystal (having three-fold improper rotation axis and two-fold axis of symmetry) has density of 2.654g/cm 3, Mohs hardness of 7, and α-β phase transition temperature of 573 ☌ at which quartz crystal is transformed from α-quartz to a hexagonal β-quartz having no piezoelectricity. Quartz crystal devices includes quartz crystal units, crystal oscillators, crystal filters, SAW devices, optical devices and so on.Ĭrystallographically, quartz crystal belongs to the trigonal system and point group symmetry 32. quartz crystal devices has become a key part essential in the modern society, as represented by the fact that even a high performance computer is "a mere box" without quartz crystal devices. Quartz crystal which converts accurate mechanical vibrations to electrical signals, is used as a source of synchronous reference signals for various types of IC, color reference signal for images, watches or the like. For this reason, quartz crystal has been used as an essential electronic component for various devices. However, quartz crystal is easily available and has the most accurate and stable frequency. Other than quartz crystal, there are materials such as ceramics in which piezoelectric effect can be confirmed. When a button is pushed or rotated, mechanical pressure is applied to piezoelectric ceramics, generating electricity (spark) for ignition. The piezoelectric effect familiar to us may be the ignition system used for lighters, stoves, burners or the like. (2) Conversely, when electricity (voltage) is applied to the surface, mechanical strain is generated. (1) When mechanical pressure is applied to a crystal unit, electricity is generated on the surface (piezoelectric effect). The piezoelectric effect was discovered in 1880 by French physicians Curie brothers. Piezoelectric effort and theory of quartz crystal This one pulse advances the second hand by one second. When the frequency of 32768Hz is continued to be divided by 2 with use of IC, the standard clock of one pulse is obtained. The representative frequency of quartz watch is 32.768kHz. This high accuracy was realized by the invention of the quartz crystal unit and IC. Quartz watches have 300 times higher accuracy than mechanical watches which used to be popular in old times. The most familiar application of quartz crystal would be quartz watches.
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