a static capacitance type yarn denier sensing arrangement is provided which includes a high frequency current source and a sensing condenser which has a pair of opposing electrodes electrically coupled with both sides of the h . f . current source and representing a passage for passing a yarn under measurement . the high frequency current from said current source is subject to amplitude modulation in response to instant denier variation of the yarn . the arrangement further includes a half wave voltage doubler rectifier circuit which is electrically connected with the sensing condenser acting as an input condenser to be included therein and an amplifier adapted for amplifying the output from the rectifier circuit .