An instrument is provided with several sensing elements to enable several parameters of a processed yarn to be measured or determined. In order to minimize the total sensing element/guide contact with the yarn within the complete process threadline, the yarn is guided through the instrument by contact only with the inlet and outlet guiding elements of the instrument and contact operative sensing elements. One particular instrument consists, in succession, of an interlace sensing device, a tension sensing device and an oil content sensing device. The electrical resistance of the yarn is measured between two pins of the oil content sensing device and in this case, the first pin is also a tension sensing pin of the instrument, and the second pin of the oil content sensing device is also the outlet guide of the instrument.