Basic principle and shortcomings of digital quartz clock

The core of quartz crystal sensor is the sensing element-piezoelectric response wafer, whose working principle is piezoelectric effect, that is, when the response crystal is subjected to mechanical stress in some directions, it will produce electric dipole; On the contrary, if a voltage is applied in a certain direction, it will deform in a specific direction, which is called the inverse piezoelectric effect. If an alternating electric field is applied to the crystal, the crystal lattice will vibrate mechanically, and when the frequency of the applied electric field is consistent with the natural oscillation frequency of the crystal, the crystal will resonate. Because the electric field intensity generated by the piezoelectric crystal under pressure is very small, it can be deformed only by a weak external electric field, which makes the piezoelectric crystal resonate easily under the excitation of an external alternating electric field. Its oscillation energy loss is small and its oscillation frequency is extremely stable. These, coupled with excellent mechanical, electrical and chemical stability, have become frequency reference elements related to digital circuits since the 1940s, such as quartz clocks, electronic watches, telephones, televisions and computers.

An interesting feature of the crystal is that when one side is energized with positive current and the other side is energized with negative current, the negative current side will shrink and bend into a U-shape. If positive and negative currents are alternately applied to both sides of the crystal regularly, the crystal will oscillate. Timing crystals are timed according to this oscillation. The built-in clock crystal of personal computer oscillates 143 18 180 times per second. This is how a quartz clock works.

The problem is that the timely crystal is defective in quality. Poor quality, it is difficult to oscillate according to the correct oscillation number. Most impurities in natural chronotropic crystals are not uniform in content and morphology, so it is necessary to use artificial chronotropic crystals. However, it is difficult to uniformly produce timely. If the accuracy is high, the error per second will be within plus or minus 65438+ one thousandth of a second; if the accuracy is low, the error per second will even reach 65438+ one thousandth of a second. 1. 10000 seconds may not feel too big, but in calculation, the daily error is 8.64 seconds, while 1 month will differ by 4 minutes. Quartz watches are not allowed for this reason.

Disturbingly, one of the characteristics of timely crystals is that the higher the temperature, the greater the error. Because there are many heating elements in personal computers, personal computer clocks are more likely to be inaccurate, and they can't be compared with quartz watches at all.