In watchmaking, compensation is about the compensation of disruptive physical effects on the accuracy of a watch.
Air pressure compensation
Compensating pendulum 1:
The Grid Pendulum
The grid pendulum compensates for the change in length of a pendulum caused by temperature fluctuations. It was invented in 1726 by John Harrison (1693 – 1776).
The pendulum lens stands with its suspension Q2 on the U-shaped metal rods Z1 and Z2 and hangs on the pendulum rod S. The material Z (dark) has approximately twice the thermal expansion coefficient of material S, so that when the pendulum heats up, the lengthening of material S (bright) below is balanced by the material of Z above and vice versa on cooling.
Compensating pendulum 2:
The mercury pendulum
In 1726, George Graham (1673 – 1751) hung a cylinder filled with mercury from a steel pendulum rod.
The mercury pendulum compensates for the change in length of a pendulum caused by temperature fluctuations.
When heated, the mercury columns rise and counteract the lengthening of the pendulum and vice versa.
Compensation pendulum 3:
The Riefler pendulum
The Riefler pendulum compensates for changes in the period of oscillation of a pendulum caused by fluctuations in temperature or air pressure.
The pendulum rod consists of an Invar steel, which is almost independent of temperature in the area of application. In addition, an aneroid barometer is used with a weight on it to compensate for changes in air pressure (higher air pressure = slower pendulum).
After Siegmund Riefler (1847-1912)
The compensation balance balances the change in the period of oscillation of a balance, which is caused by temperature fluctuations.
Compensation balance with bimetal ring: (1) If you change the position of opposite screw pairs in the direction of the slots, the temperature compensation is increased. (2) Partially unscrewing opposing pairs of screws slows down the frequency. If only one screw is partially unscrewed, the center of gravity changes.
Image: released as public domain
This rotating pendulum clock with mercury compensation is a rarity. Just like a figure skater who takes her arms outward in a piroutte in order to turn more slowly, the body of revolution expands when heated and becomes slower. However, the mercury expands in the tubes inclined inwards and the torque does not change.
However, since clocks with a rotary pendulum react very sensitively to even minor vibrations, the location must first be designed to be vibration-free before such a compensation can develop its effect.