The first version was actually patented, so we know how that one worked fully. The latest versions are secretive but they still likely measure the same thing.
https://www.cs.cmu.edu/~dst/Secrets/E-Meter/hubbard-patent.html
The first version was actually patented, so we know how that one worked fully. The latest versions are secretive but they still likely measure the same thing.
https://www.cs.cmu.edu/~dst/Secrets/E-Meter/hubbard-patent.html