Patent ID: 7193233

Claim:
A flowmeter for providing a signal indicating fluid flow rate through the flowmeter, said flowmeter of the type having a vertical, tapered duct defined by a duct wall and having an axis extending the length of the duct, a first opening for receiving flow of fluid whose flow rate is to be measured, and a second opening from which the fluid exits the duct, and a float shifting position along the duct axis within the duct and whose vertical position in the duct indicates the fluid flow rate, said flowmeter further comprising: a) a window forming a portion of the duct wall in alignment with the duct axis, said window transparent to light and positioned adjacent to one opening of the duct; b) a light source external to the duct and adjacent to the window, and transmitting light through the window toward the float; c) a feature of the float that returns to the window a portion of the light shining on the float; and e) a light sensor external to the duct and receiving through the window, light returned from the float previously transmitted toward the float, and providing a sensor signal indicating the level of light received by the light sensor.