An autonomous bladder pressure monitoring system

This paper reports on the development of an autonomous monitoring system, capable of continuously measuring the pressure inside the bladder. The capsule features wireless bi-directional communication and can be inductively powered anywhere inside the bladder. Short-circuiting the resonant LC tank for the data transmission maximizes the operating range of the passive telemetry. A novel clock extraction method is presented, based on lock-in of a Schmitt-trigger oscillator into the external radio-frequency field. A prototype was built using only discrete components. The system measures the pressure with a resolution of 0.04 kPa at a sampling rate of 10 Hz.