A spinning assembly has a fibre (2) draw unit (1a) with a sensor (3, 30) measuring the thickness of the fibre supply at the inlet and/or outlet. The assembly further has sensors measuring fibre temperature (40, 41) at the draw unit (1a) outlet, and a compensation unit (4, 31; 10) which corrects the thickness sensor (3, 30) measurements using temperature information. claimed are a number of different spinning machine configurations incorporating a fibre (2) draw unit (1a) incorporating microwave sensors (3, 30). Also claimed is a sensor cleaning system, further claimed is a fibre feed assembly which automatically introduces fibres into the machine for measurement, and a thread compressor.