Time based interface detection systems for blood processing apparatus

摘要

A system for monitoring the interface region between cellular constituents and plasma in a blood separation chamber employs a sensor mechanism for emitting upon the interface region energy that is absorbed by the cellular constituents. The sensor mechanism also detects the intensity of the energy that is not absorbed by the interface region to generate an unabsorbed intensity output signal. The system moves the interface region relative to the sensor mechanism during a prescribed time period. A first circuit measures variations in the unabsorbed intensity output signal over the prescribed time period and generates a time based output. A second circuit can derive the physical size of the interface region based upon the time based output.