Similar to the Elizabeth Tower clock aka "Big Ben", this 'pendulum' clock betters 1 second/month accuracy and uses Linux for data aquisition: "The pendulum is fitted with an infrared optic sensor which is occluded four times per period producing a rectangular wave. The amplitude at the sensor is about 50mm (100mm peak-peak) and the distance from the fulcrum to the sensor is, conveniently, about 1m - hence the amplitude can be measured in mm or mrad interchangeably.

A GPS receiver generates a 1pps square wave. This signal is accurate to 10ns, so they say. The infrared signal and the GPS signal are digitised simultaneously by a datalogger (ADC). Some clever data processing permits the pendulum period and amplitude to be deduced to high accuracy, once every 3 seconds.

A weather station measures temperature, pressure and humidity. Air density is calculated from these three properties according to an accepted formula. The data is logged once every 10 minutes.

All the data is saved on a local PC running OpenSuse (Linux). The data processing is performed in C++. Data is uploaded to the server every 3 hours."

http://trin-hosts.trin.cam.ac.uk/clo...nstrumentation

http://trin-hosts.trin.cam.ac.uk/clo...umentation.pdf

Hi,

Interesting!!

A very pleasant afternoon diversion, thanks!

Your welcome.
@onebuck It was interesting. I saw a link and a reference to linux in my Twitter feed that led me to the site. On the way I read some material on the history of the big pendulum clocks. I, like many people, have a tendency to forget just how clever our forebears were.

That's a Keeper.