Patent ID: 9366560
Filing Date: 2016-06-14
CPC Classification: G01F

Claim Text:
1. A detector for detecting a change in fluid level in a tube; said tube being constructed of a material that at least partially transmits light; a light source mounted on one side of said tube for emitting light and a photodetector mounted on an opposite side of said tube for receiving said light; said light and said photodetector being mounted at a first predetermined location along said tube proximate a location of fluid level change, said photodetector receiving a first input voltage and providing an output voltage when receiving said light, said output voltage of said photodetector varying with the intensity of light received; a NAND gate receiving a second input voltage, less than the first input voltage and said NAND gate further receiving said output voltage directly from said photodetector at multiple inputs of said NAND gate, said NAND gate having an output which changes from one state to a second state when said output voltage of said photodetector reaches a predetermined voltage, said NAND gate including predetermined supply voltages and components biasing at least one solid state device therein to switch between a first state and a second state at said predetermined voltage, said predetermined voltage being within a range of output voltages of said photodetector, the rate of voltage difference change between said first and said second states being significantly faster than the voltage variation rate of said output of said photodetector; and a driver circuit, said driver circuit having impedance output value suitable for matching impedance of a line to a remote location, said driver receiving said output of said NAND gate and providing a signal at the impedance output value for transmission to a remote location to indicate whether fluid in said tube is above or below said predetermined location.