Twin optical sensor based instrument for the measurement of weft velocity in air-jet weaving

A previous paper described the effectiveness and application advantages provided by a single opto-electronic sensor based instrument for weft velocity measurement in air-jet weaving. Consideration of further refinement of the instrument, particularly for improving the smoothness of the weft velocity curve obtained by using it, indicated possible advantages of developing it as a twin sensor based design. This would enable two time related data streams and their analysis by use of the cross-correlation technique, which would primarily help in reducing errors of weft velocity determination due to possible variation of the uniformity of center distance between yarn markings. This paper reports on the evaluation of the performance of the modified instrument which was found to be superior to that of the single sensor based device. More significantly, given the ease with which a large number of repetitive measurements can be made using it, this development also led to the very useful outcome that it enables obtaining a close estimate of the ‘true’ weft velocity curve for a given set of weft insertion settings. The overall size of the modified sensor has remained the same as before, so mounting it on the weaving machine is just as simple as before.