Wall Clocks

A pendulum clock is a clock that uses a pendulum, a swinging weight, as its time base. From their invention in 1656 until the 1930s, pendulum clocks were the world's most accurate timekeepers, accounting for their widespread use. more...

Home
A/V Accessories & Cables
DVD & Home Theater
Gadgets & Other Electronics
Air Purifiers
Breathalyzers
Calculators
Dictionaries & Translators
Digital Clocks & Clock...
Alarm Clocks
Ambient Noise Alarm Clocks
Clock Radios
Clock Radios with CD Players
Travel Alarm Clocks
Wall Clocks
eBooks
Flashlight Key Chains
Fresnel Lenses
Home Automation
Language Filters
Laser Pointers
Metal Detectors
Other Gadgets
Polygraphs
Radiation Detectors
RF Locators
Surveillance
Therapeutic Devices
Timers
Voltage Converters
Weather Devices
Heating, Cooling & Air
Home Audio
Lamps, Lighting, Ceiling...
Major Appliances
Outdoor Power Equipment
Satellite, Cable TV
Televisions
Vacuum Cleaners &...

Pendulum clocks cannot operate in vehicles; the motion and accelerations of the vehicle will affect the motion of the pendulum, causing inaccuracies. They are now kept mostly for their decorative and antique value.

History

The pendulum clock was invented and patented by Christiaan Huygens in 1656, probably inspired by the research into pendulums by Galileo Galilei. Galileo had the idea for a pendulum clock in 1637, partly constructed by his son in 1649, but they didn't live to finish it. The introduction of the pendulum increased the accuracy of clocks by a factor of 100, leading to their rapid spread as existing clocks were retrofitted with pendulums.

These early clocks, due to their verge escapements, had wide pendulum swings of up to 100°. Huygens discovered that wide swings made the pendulum's period, and thus the rate of the clock, vary with changes in the driving force. Clockmakers' realization that only pendulums with small swings of a few degrees are isochronous motivated the invention of the anchor escapement in 1670, which reduced the pendulum's swing to 4°-6°. This allowed the clock's case to accomodate longer, slower pendulums, which caused less wear on the movement. The seconds pendulum, in which each swing takes one second, which is about one meter long, became popular. The long narrow clocks built around these pendulums, first made by William Clement, became known as grandfather clocks. The increased accuracy resulting from these developments caused the minute hand, previously rare, to be added to clock faces beginning around 1690.

Until the 1800s, clocks were made by individual craftsmen and were very expensive. The rich ornamentation of clocks of this period indicates their value as status symbols of the wealthy. In the 1800s, factory production of clock parts gradually made pendulum clocks affordable by middle class families.

Daily life was organized around the home pendulum clock. More accurate pendulum clocks, called regulators, were installed in places of business and used to schedule work and set other clocks. The most accurate, known as astronomical regulators, were used in observatories. Beginning in the Industrial Revolution, astronomical regulators in naval observatories served as primary standards for national time distribution services. The US National Bureau of Standards (now NIST) based the US time standard on Riefler pendulum clocks from 1909, accurate to about 10 milliseconds per day. In 1929 it switched to the Shortt free pendulum clock before phasing in quartz standards in the 1930s. With error less than one second per year, it was probably the most accurate commercially produced pendulum clock.

Read more at Wikipedia.org