Reason For Accuracy
A pendulum swinging in a vacuum at a constant amplitude free of external disturbances theoretically keeps perfect time. However, pendulums in clocks have to be linked to the clock's mechanism, which disturbs their natural swing, and this was the main cause of error in precision clocks of the early 20th century. An ordinary clock's mechanism interacts with the pendulum each swing to perform two functions: first, the pendulum must activate some kind of linkage to record the passage of time. Second, the clock's mechanism, triggered by the linkage, must give the pendulum a push (impulse) to replace the energy the pendulum loses to friction, to keep it swinging. These two functions both disturb the pendulum's motion.
The advantages of the Shortt clock are first, it reduced the disturbance of the master pendulum due to the impulse by only giving the pendulums an impulse once every 30 seconds exactly (30 pendulum swings), and second, it eliminated all other interaction with the master pendulum by generating the necessary precise timing signal to control the slave clock (and record the passage of time) from the impulse mechanism itself, leaving the pendulum to swing "free" of interference.
Read more about this topic: Shortt-Synchronome Clock
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