Analog clock parts
A wall clock showing the time at 10:09
A clock face or is the part of an analog clock (or watch) that displays the time through the use of a fixed-numbered dial or dials and moving hands. In its most basic form, recognized throughout the world, the periphery of the dial is numbered 1 through 12 indicating the hours in a 12-hour cycle, and a short makes two revolutions in a day. A longer makes one revolution every hour. The face may also include a which makes one revolution per minute. The term is less commonly used for the time display on digital clocks and watches.
A second type of clock face is the 24-hour analog dial, widely used in military and other organizations that use 24-hour time. This is similar to the 12-hour dial above, except it has hours numbered 1–24 around the outside, and the hour hand makes only one revolution per day. Some special-purpose clocks, such as timers and sporting event clocks, are designed for measuring periods less than one hour. Clocks can indicate the hour with Roman numerals or Hindu–Arabic numerals, or with non-numeric indicator marks. The two numbering systems have also been used in combination, with the prior indicating the hour and the later the minute. Longcase clocks (grandfather clocks) typically use Roman numerals for the hours. Clocks using only Arabic numerals first began to appear in the mid-18th century.
The periphery of a clock's face, where the numbers and other graduations appear, is often called the chapter ring.
The clock face is so familiar that the numbers are often omitted and replaced with undifferentiated hour marks, particularly in the case of watches. Occasionally markings of any sort are dispensed with, and the time is read by the angles of the hands. The face of the Movado "Museum Watch" is known for a single dot at the 12 o'clock position.
Reading a modern clock face'12:14' in both analog and digital representations. In the analog clock, the minute hand is on "14" minutes, and the hour hand is moving from '12' to '1' - this indicates a time of 12:14.
Most modern clocks have the numbers 1 through 12 printed at equally spaced intervals around the periphery of the face with the 12 at the top, indicating the hour, and on many models, sixty dots or lines evenly spaced in a ring around the outside of the dial, indicating minutes and seconds. The time is read by observing the placement of several "hands" which emanate from the centre of the dial:
- A short thick "hour" hand;
- A long, thinner "minute" hand;
- On some models, a very thin "second" hand
All the hands continuously rotate around the dial in a 'clockwise' direction – in the direction of increasing numbers.
- The second or sweep hand moves relatively quickly, taking a full minute (sixty seconds) to make a complete rotation from '12 to 12.' For every rotation of the second hand, the minute hand will move from one minute mark to the next.
- The minute hand rotates more slowly around the dial, it takes one hour (sixty minutes) to make a complete rotation from '12 to 12.' For every rotation of the minute hand, the hour hand will move from one hour mark to the next.
- The hour hand moves slowest of all, taking twelve hours (half a day) to make a complete rotation. It starts from '12' at midnight, makes one rotation until it is pointing at '12' again at noon, then makes another rotation until it is pointing at '12' again at midnight of the next night.
Clocks existed before clock faces. The first mechanical clocks, built in 13th-century Europe, were striking clocks: their purpose was to ring bells upon the canonical hours, to call the public to prayer. These were erected as tower clocks in public places, to ensure that the bells were audible. It was not until these mechanical clocks were in place that their creators realized that their wheels could be used to drive an indicator on a dial on the outside of the tower, where it could be widely seen.