Patent ID: 7234787

Claim:
A sensing system for detecting the presence of liquid at a predetermined level comprising: a reservoir including a first wall section and a second wall section forming an angle with the first wall section, wherein at least a portion of the first wall section and a portion of the second wall section are substantially transmissive to light; a light emitter located proximate to the first wall section and positioned at the predetermined level; a photo detector positioned at the predetermined level and located proximate to the second wall section for detecting the light emitted from the light emitter, the light emitter being oriented to direct light through said first and second wall sections toward the photodetector, the light from the light emitter following a first path through said first and second wall sections when liquid is present in the reservoir at the predetermined level and following a second path through said first and second wall sections when liquid is not present in the reservoir at the predetermined level, the photodetector receiving the light from the light emitter traveling only one of the first path or the second path.