Metal tape transducer for the micrometric measurement linear quantities

A transducer for the micrometric measurement of linear quantities, of the type comprising a support rule having ends, a thin continuous metal tape of cross-section less than 1 mm.sup.2 on which a plurality of measurement notches are engraved at regular micrometric intervals, said notches being engraved while said tape is under a tension at which the tape is to be maintained, and which is fixed to said support rule, a reading head which moves axially relative to the tape in order to sense the measurement notches, said reading head being supported slidably along said support rule, means at the ends of said support rule to suspend and keep taut ends of the tape under a predetermined constant tension, said reading head comprising a guide groove coaxial to the tape, in which the tape slides freely when the head moves relative to the tape.