A digital clock is a type of clock that displays the time digitally (i.e. in numerals or other symbols), as opposed to an analog clock, where the time is indicated by the positions of rotating hands.
Digital clocks are often associated with electronic drives, but the “digital” description refers only to the display, not to the drive mechanism. (Both analog and digital clocks can be driven either mechanically or electronically, but “clockwork” mechanisms with digital displays are rare.) The biggest digital clock is the Lichtzelt Pegel (“Light Time Level”) on the television tower Rheinturm Düsseldorf, Germany.
Digital clocks typically use the 50 or 60 hertz oscillation of AC power or a 32,768 hertz crystal oscillator as in a quartz clock to keep time. Most digital clocks display the hour of the day in 24-hour format; in the United States and a few other countries, a more commonly used hour sequence option is 12-hour format (with some indication of AM or PM). Some timepieces, such as many digital watches, can be switched between 12-hour and 24-hour modes. Emulations of analog-style faces often use an LCD screen, and these are also sometimes described as “digital”
The trouble with pendulum clocks and ordinary watches is that you have to keep remembering to wind them. If you forget, they stop—and you have no idea what time it is. Another difficulty with pendulum clocks is that they depend on the force of gravity, which varies very slightly from place to place; that means a pendulum clock tells time differently at high altitudes from at sea level! Pendulums also change length as the temperature changes, expanding slightly on warm days and contracting on cold days, which makes them less accurate again.
Quartz watches solve all these problems. They are battery powered and, because they use so little electricity, the battery can often last several years before you need to replace it. They are also much more accurate than pendulum clocks. Quartz watches work in a very different way to pendulum clocks and ordinary watches. They still have gears inside them to count the seconds, minutes, and hours and sweep the hands around the clockface. But the gears are regulated by a tiny crystal of quartz instead of a swinging pendulum or a moving balance wheel. Gravity doesn’t figure in the workings at all so a quartz clock tells the time just as well when you’re climbing Mount Everest as it does when you’re at sea.
Wearable technology is often used to monitor a user’s health. Given that such a device is in close contact with the user, it can easily collect data.
Wearables can be used to collect data on a user’s health including:
- Heart rate
- Calories burned
- Steps walked
- Blood pressure
- Time spent exercising
These functions are often bundled together in a single unit, like an activity tracker or a smartwatch like the Apple Watch Series 2 or Samsung Galaxy Gear Sport. Devices like these are used for physical training and monitoring overall physical health.
Currently other applications within healthcare are being explored, such as:
- Measuring blood alcohol content
- Measuring athletic performance
- Monitoring how sick the user is
- Health Risk Assessment applications, including measures of frailty and risks of age-dependent diseases
While wearables can collect data in aggregate form, they have yet to analyze or make conclusions based on this data. Wearables cannot account for the differing health needs of an individual; they can only collect data. Because of this, wearables are used primarily for information about general well-being but not for making decisions about one’s health.