980. What is a digital display and how does it work?
The term "digital display" usually refers to a system that reports the value of a physical quantity in numerical form. A digital watch display is a good example. The physical quantity it reports is time and it makes its report in the form of hours, minutes, and second—all in numerical form. In a digital watch, the display makes use of liquid crystals that are sensitive to electric fields. When you look at the display, you are actually looking through a layer of polarizing filter, some transparent electric wires, and a layer of liquid crystals. Liquid crystals are liquids that contain molecules that naturally orient themselves relative to one another. In the display, these liquid crystals adopt different orientations when they are exposed to electric fields than when they're not exposed to such fields. This electrically altered orientation affects their optical properties and causes them to appear dark when viewed through the polarizing filter. The watch can control the appearance of each segment of its digital display by the pattern of electric charge on its transparent wires. Since it takes very little energy to change the orientation of the liquid crystals, the watch uses almost no power for its display and can operate for years on a button battery.