A differential pressure flow sensor system comprises a disposable flow sensor which has upstream and downstream pressure sensing devices for detecting a differential pressure in a flow channel. Each sensing device comprises a diaphragm, a capacitor and an inductor electrically coupled to the capacitor so as to form an LC tank circuit. The capacitor and/or inductor can be mechanically coupled to the diaphragm such that a deflection of the diaphragm in response to fluid pressure applied thereto causes a change in the resonant frequency of the LC tank. The differential pressure and flow rate can be determined by detecting changes in the resonant frequency using interrogation electronics which can wirelessly interrogate the devices. A calibration capacitor and/or inductor can be formed on each sensing device and trimmed thereon for calibration purposes. Such pressure flow systems can be implemented in medical applications.