The field of control engineering began with mechanical clocks thousands of years ago.
The water clock and sundial are the oldest time keepers known in history. While the sundial would keep track of the sun using the shadow, the water clock would keep track of time similar to today’s sand timer. In Egypt the device was carefully designed so that water would exit the “bucket” at an even rate and markings would show the passage of minutes or hours as it drained. The device was improved by the Greeks and Romans.
Eventually clocks made of gears and springs were developed. In the last unit we showed a “hairspring” also known as balance spring which kept the ammeter at zero (left) and applied an even pressure in the reverse direction no matter how much the needle moved to the right. It was clock makers who helped early electric pioneers with this mechanism.
There are many forms of mechanical clocks, however they all suffer from inaccuracies due to expansion of materials and other issues. In the video below John Lowe from NIST tells us about the problems with mechanical clocks:
Now lets move on to staple in modern clocks, the quartz clock.