Patent ID: 7633398

Claim:
An instrument for measuring precipitation comprising: a support structure; a plurality of light sensors disposed in a vertical arrangement on said support structure and a plurality of light sources disposed in a vertical arrangement on said support structure, each said light sensor being spaced a predetermined distance from each adjacent light sensor and positioned to receive light from at least one said light sensor and each said light sensor being spaced a predetermined distance from each adjacent said light source, each light sensor being capable of generating an output signal in response to light received from one of said light sources; and a microprocessor that receives said output signal from at least one of said light sensors and determines the presence or absence of an accumulation of precipitation based on said signal, wherein the microprocessor is programmed to receive a signal from each of said light sensors when precipitation is absent from said support structure and to compare each said signal with an initial signal from each of said light sensors when precipitation is absent to determine when any of said light sensors or light sources or both light sensors and light sources may require cleaning.