the sole 10 and needle plate 12 of the sewing machine a support 15 is fixed to presser bar 8 by means of a screw 14 and comprises a head 16 and a sleeve 17 which surrounds presser bar 8 a catch ring 18 is secured to the lower portion of sleeve 17 by means of a screw 19 and is provided with a catch 20 projecting upwardly and extending in the radial direction of the ring above catch ring 18 and supported thereon a mounting ring 21 of a holder 22 is guided on sleeve 17 on its underside mounting ring 21 is provided with two catch grooves 23 and 24 which extend perpendicularly to each other and serve the prupose of receiving catch 20 of catch ring 18 mounting ring 21 is held in its locked position by means of a compression spring 25 which is provided on sleeve 17 between head 16 and ring 21 holder 22 carries an annular extension 28 which is provided with a recess 26 for a measuring coil 27 and surrounds the path of sewing needle 6 measuring coil 27 comprises a carrier body of ceramic material which is provided with several turns of enamel to cover wire measuring coil 27 has.