A kind of flow sensor sub-component for the flowing for being used to sense fluid medicament, it includes flow tube, and flow tube has flow tube entrance and flow tube outlet and acoustic transmission ratio.Medicament flows through flow tube.First piezoelectric element arrangement is in the upstream position of flow tube, and the second piezoelectric element arrangement is in the downstream position of flow tube so that the first piezoelectric element and the second piezoelectric element are installed into be separated from each other with presetting distance.Absorber sheath is around flow tube.Absorber sheath has upstream end thereof and downstream end.Absorber sheath is made of the material with the acoustic transmission ratio different from flow tube.
