The transducer has a magnetic circuit (4) with a magnetic core. A magnetic field detector (5) has a detection cell (25) arranged in an air-gap formed between ends of the core. The circuit has a clamp (21) soldered with the core on either side of the air-gap. The detector has a supporting plate over which the cell is mounted. The plate has a notch facing the detection cell, in which one end of the core is arranged.
