Computer Laboratory

Introduction to Joule

Sankey Diagrams

Tree Map Diagrams

File Formats

Recovering Carbon Information

Meter Data

The meter data files provide the bulk of the information used by Joule. Files for a meter should be named as

S-m<meter number>/S-m<meter number>-YYYY-MM.json

so that all files for a particular meter are in the same directory. Further all of the meter directories must belong to the same parent directory. For example

http://www.cl.cam.ac.uk/meters/elec/published/S-m37/S-m37-2013-09.json

is the file for meter 37 in the Computer Lab for the month of September 2013. Here are its contents (you will need to scroll to see all of it):

The fields at the beginning are intended to be helpful in understanding what is being measured (and are ignored by Joule - the tree file contains the date file meta-information used by Joule.) The information that Joule does use is the data object in the file. The data object has three components:

  • a start time as a JavaScript time stamp, i.e. milliseconds since 1 January 1970
  • a step time in milliseconds between readings (so in the example above the samples are at hourly intervals)
  • an array of readings in kilowatts, the first being for the time denoted by the start time.