C-magnétique

15:26 Nov 20, 2019 

The C could also stand for "champ".

13:59 Nov 20, 2019 

As ever your expertise is invaluable. Sorry about the lack of picture. As I say, the referenced pieces said to be there are not numbered as claimed in the text. There are no obviously C-shaped pieces.

13:52 Nov 20, 2019 

how you interpret "comprennent", eg the set of all current sensors may include "C-magnetiques" or these specific current sensors may themselves incorporate "C-magnetiques". But this doesn't really answer your question; the (almost) only non-invasive way to measure current is to measure the associated magnetic field, for which a variety of techniques exist. To the best of my knowledge, none of these involves a C-shaped sensor unless you include current clamps - these are hinged soft-iron clamps which encircle the wire such that the induced magnetic field circulates around the clamp. A picture of what the author has in mind would really help! It is just possible that the "C" stands for "courant", i.e. magnetic current (as opposed to electric current).