An auxiliary element includes an end plate having an inner face which is intended to be applied against a large surface of a sensor and an outer face which bears two spaced-apart mounting lugs on a first edge thereof, the lugs extending outwards perpendicularly to the outer face. A first pair of passages is formed in the lugs for first screws used to fix the auxiliary element to a support. In addition, the end plate includes a through opening for the electrical conductor and a second pair of passages, symmetrically on either side of the opening, for second screws used to fix the end plate to the sensor. The through opening is formed by a recess provided on a second edge, opposite the first edge, and the second pair of passages are formed by two parallel slits which extend perpendicularly to the first edge of the end plate.