the micrometer range with the outer layers 3 and 4 being grounded so as to shield the electrical conductors and connections formed with the layer 5 from external electrical fields the insulating layers 6 and 7 are preferably substantially thicker than the electrically conductive layers 3 4 and 5 so as to achieve a rigid mechanical sandwich construction the sensor element shown in fig3 is designed so that it can be inserted between the drop wires 23 of the reed 18 and has thicknesses of less than 1 mm the edge of the sensor element 2 close to the weft channel 19 of the profiled reed 18 follows the contours of the reed 18 the laminated construction of the sensor element 2 is achieved with a multi layer printed circuit board for example the middle electrically conductive layer 5 of the sensor element 2 is preferably made from a metal such as copper for example and has a thickness of a few micrometers the actual feeler 5a is constructed as an open loop in the present exemplified embodiment from this electrically conductive layer 5 with the feeler 5a surrounding the weft channel 19 inside the profiled reed 18 so that the cross section of the weft channel 19 is not reduced by the sensor element 2 of course the feeler 5a can naturally be constructed with different shapes thus for example only with the lower half of the shape shown in fig3 together with the feeler 5a the middle layer 5 comprises a conductive connection 5b from the feeler 5a to a charge amplifier 10 further conductive connections or shielding grounded layers can be formed from the middle layer 5 in fig3.