Quartz watches

The measurement of mechanical properties is a major part of the domain of characterisation. The tensile test is the key procedure, and this in turn is linked with the various tests to measure fracture toughness... crudely speaking, the capacity to withstand the weakening effects of defects. Elaborate test procedures have been developed to examine resistance to high-speed impact of projectiles, a property of civil (birdstrike on aircraft) as well as military importance. Another kind of lest is needed to measure the elastic moduli in different directions of an anisotropic crystal this is, for instance, vital for the proper exploitation of quartz crystal slices in quartz watches. 

Alpha-quartz has many useful properties which lead to its wide use in industry as a glass, ceramic and molecular sieve. However, undoubtedly its most technically important use occurs by virtue of its piezo-electric properties, which allow it to be used as a frequency regulating device in satellites, computers, and the ubiquitous quartz-watch . Unfortunately, it has been found that quartz crystals are susceptible to damage by radiation, and that this is associated with the presence of defects in the crystal lattice. These defects, particularly aluminum and hydrogen, are grown into the crystal and so far have proved impossible to remove. This problem has been the cause of intensive research, which has led to some information on the possible types of defects involved, but has failed to produce details of their geometries, and the way in which they interact. 

A slice of quartz develops a net positive charge on one side and a net negative charge on the other side when pressure is applied. The same effect is found when pressure is applied by means of an alternating electric field. This effect is known as the piezoelectric effect and is used for quartz watches and clocks, TVs, hearing aids, etc. 

Nanostructured Li and Ni containing nickel-metal hydride batteries are widely used in cell phones, video camcorders, quartz watches, and pacemakers to name a few uses. Electrically conducting nanostructured mesoporous materials are envisaged as new materials for fuel cell applications, batteries, and ultracapacitors. 

Piezoelectricity is the operating principle of quartz watches. In these devices, a tiny crystal of quartz oscillates at a frequency of 32 kHz in response to an electrical charge generated from the battery. In general, the overall size and composition of a piezoelectric crystal will affect its oscillation frequency. Since quartz loses very little energy upon vibration, the integrated circuit (IC, see Chapter 4) within a watch is used to reduce the repeatable oscillations into electric pulses, which are displayed as hours, minutes, and seconds on the watch face. 

Electromagnets in indicating instruments, fire detection, quartz watches, electromechanical devices... 

IhemOTb Tihe dii wce between precision and accuracy A digital quartz watch may display the time precisely to fractions of a second, but will still tell the wrong time if not properly set. A correctly adjusted analogue watch (with hands ) may only display the time to the nearest minute, but it can still be the more accurate. 

The vibration induced by E allows the frequency of an electric resonant circuit (used, for example, in a quartz watch) to be stabilized. Quartz is also used in the manufacture of acoustic generators. The theory which accounts for this dynamic effect comprises the calculation of the elastic vibrations of the crystal (Section 4.4.3) induced by an alternating electric field E cos cot parallel to in the absence of external stresses. The importance of quartz is due to the fact that it is chemically inert and very stable, and, even if the elastic and piezoelectric constants vary with temperature, it is possible to cut crystal plates with orientations such that their natural frequencies are constant over a large temperature... 

Electromagnets in indicating instruments, fire detection, quartz watches, electromechanical devices Magnetic yokes in permanent magnet devices, such as lifting and holding magnets, loudspeakers... 

Thus there are many piezo devices using these phenomena. Microphone membranes (PE), loud speakers (RPE), sonar (historically the first application RPE), piezoresistors (PR) for pressure measurements, cigarette lighters (PE), and quartz watches (RPE) are examples. 

Ceramic materials play an important role in the electronics industry. Semiconductor integrated circuits are typically mounted on a ceramic substrate, usually alumina. Some ceramics, notably quartz (crystalline Si02), are piezoelectric, which means that they generate an electrical potential when subjected to mechanical stress. This property enables us to use piezoelectric materials to control frequencies in electronic circuits, as in quartz watches and ultrasonic generators. 

Some of the types of Si02 employed for industrial purposes include high-purity a-quartz, vitreous silica, silica gels, and diatomaceous earth. The use of very pure quartz crystals in oscillators and other electromechanical devices constitutes one of the most important applications of high-grade quartz. Such oscillators are the heart of quartz watches and also enable radio stations to remain on an assigned frequency. 

The intermetallic compound SmCo, with markedly ferromagnetic properties, was invented in the 1970s. Rare earth metals are nowadays very much used in magnetic alloys, for instance samarium-miniaturized systems. Still better is the compound Sm COj with a certain content also of iron, copper and zirconium. For heavier magnets, alloys of neodymium, iron and boron are used. 

Today, microprocessors are everywhere. Of course, they are in your computer and calculator, but microprocessors are also in many simple things we take for granted. Personal stereos, appliances with digital displays, automobiles with exhaust emission controls, even quartz watches and clocks (jumping second hand) all are controlled by microprocessors. One of the most common uses for microprocessors in the United States today is for controlling traffic lights. 

The unit of time, the second, is abbreviated by small s (and not sec). For all measurement purposes it is the ephemeris second, the properly fked fraction of the mean solar year 1900. The SI unit is chosen to match this time-interval closely using a cesium 133 clock. This definition makes the SI time independent of the astronomical time. The cesium 133 clock is capable of an accuracy of one part in 10. An ordinary stopwatch, not even a quartz watch, is usually sufficient for thermal analysis experiments. 

These are used in analogue quartz watches and pulsing electronic devices. 

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