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)

12 Sep 2014 [09:00]
ADJUST: +300 ms/day to 39600, and a top-up wind. Aiming for zero at time-change on Sat 25 Oct. We will see!
09 Sep 2014 [14:00]
top-up wind
08 Sep 2014 [18:00]
01 Sep 2014 [14:45]
Barry James from Romax did a top-up wind
30 Aug 2014 [16:00]
Ipswich branch of the British Horological Institute and the Bury St Edmunds Branch of the Antiquarian Horological Society visited today and did a top-up wind
27 Aug 2014 [19:00]
top-up wind with Martin Kyte (MRC LMB) - he wants to build a tower clock with a double 3 legged escapement!
24 Aug 2014 [18:45]
winding and computer restart, trying to get weatherlogger to work!
20 Aug 2014 [16:00]
computer restart, and top-up wind by Hilary Costello
17 Aug 2014 [20:00]
winding by team Canada: Stephan Bots, Rick Enns, Hilary Costello