Patent ID: 8876757

Claim:
A medical device, comprising: a plurality of transmitters and a numerically matching plurality of receivers forming transmitter-receiver pairs positioned in association with a fluid maintaining device associated with the medical device; circuitry configured to drive the transmitter to transmit light energy to said fluid maintaining device; and a controller configured to receive data from the receiver and determine fluid level in said fluid maintaining device; wherein each transmitter of the plurality of transmitters is configured to transmit light energy at a predetermined wavelength forming a signal distinct from the other of the plurality of transmitters, each receiver of the plurality of receivers continuously receives light energy from the paired transmitter when the paired transmitter transmits light energy, and the controller is further configured to determine presence and absence of fluid in said fluid maintaining device based on an amount of light energy received at each receiver of the plurality of receivers; wherein the amount of light energy received at each receiver of the plurality of receivers is based on the predetermined wavelength of the light energy, a distance between the transmitter and the receiver of the transmitter-receiver pair, and an absorption coefficient for fluid expected to be employed in the fluid maintaining device, such that light energy below a predetermined nonzero value received at a receiver of the plurality of receivers indicates fluid presence at the receiver level in the fluid maintaining device and light energy above the predetermined nonzero value received at a receiver of the plurality of receivers indicates an absence of fluid at the receiver level in the fluid maintaining device.