The pendulum clock in Trinity College, Cambridge was installed in 1910. It is remarkably accurate, known to be better than one second per month. In 2009 a system was installed to monitor the "going". The work was done as part of a 4th year MEng project at the Engineering Department. A sensor on the pendulum detects the going of the clock, which is compared to the accurate time signal from a GPS receiver.

Here is a graph for the last 30 days of drift (updated every 3 hours):

For an entirely mechanical clock the accuracy is remarkable.

A barometric compensator was installed at clock change - midnight 28 March 2010.

The clock is regulated as infrequently as possible so as to stay within +/- 5 seconds of the correct time. This enables the steady-state physics of the clock to be examined without unnecessary interference.

The black dots ● indicate that there is a comment relating to the time indicated. Blue arrows pointing down indicate that an adjustment was made to the Going of the clock by removing weights from the pendulum. Red arrows up indicate addition of weights to speed the clock up.

Comments (see all | edit)

14 Aug 2014 [14:01]
winding by Mark Rainer and (mostly) Daniel Flack - his first time!
10 Aug 2014 [14:50]
reset drift correction by restarting clocklogger after changing the value of last_drift from 4.1 to 1.1
07 Aug 2014 [14:20]
thanks to Mark Rainer for winding
01 Aug 2014 [16:05]
Winding by Pauline Smith, Senior Porter - her first time!
27 Jul 2014 [23:00]
wind, and it is very hot up there!
25 Jul 2014 [12:30]
The weather station is back online! many thanks to Rick Lupton for his help, so near to his wedding...