Optical monitoring system pressure

A method of monitoring pressure in an infusion set for administering a solution to a patient, the method comprising: selecting a sensor (16, 36, 99) of optical signals having a transmitter (8, 28, 68, 88) optical signals and a receiver (12, 32, 72, 92) of optical signals; characterized by placing a tube (4, 24, 64, 84) of an infusion set, adjacent to the sensor (16, 36, 76, 96) of optical signals so that the receiver (12, 32, 72, 92) optical signals is disposed on one side of the tube (4, 24, 64, 84) opposite the transmitter (8, 28, 68, 88) of optical signals for changes in the diameter of the tube (4, 24, 64, 84) change an amount of optical signals detected by the receiver (12, 32, 72, 92) of optical signals; and generate a voltage indicative of the obstruction of light by the tube (4, 24, 64, 84) of the infusion set and determine the pressure in the infusion set from the voltage.