Photo electrical sensor

Claim 2

A sensor comprising a pair of communicating equilevel columns of liquid, means for longitudinally projecting a beam of light through each of said columns of liquid, electro-optical light detecting means associated with each of said columns oF liquid for supplying an electrical output level as a function of the amount of light detected thereby, and calibration means comprising a light masking member adjustably projecting into one of said beams of light for originally establishing a base reference for said output level, whereby any deviations of said output level from said base reference is a function of a differential change in length of said columns of liquid causing a differential change in the amount of light detected by said light detecting means.

Claim 3

The sensor of claim 1 wherein said columns of liquid are disposed substantially in a vertical plane.

Claim 4

The sensor of claim 1 wherein said beams of light are obtained from a common light source.

Claim 5

The sensor of claim 3 wherein said common light source is disposed so as to illuminate a block of light transmissive material in contact with said columns of liquid.

Claim 6

A sensor comprising a housing, a pair of bores disposed in said housing, a third bore in said housing placing the bores of said pair in communication with each other, a liquid filling said bores to a predetermined common level above said third bore, a light source, means for projecting a beam of light from said light source through each of said bores of said pair from an end thereof, a pair of photo-cells having an electrical resistance varying as a function of the amount of light impinging thereon each disposed at the other end of each of said bores of said pair, said photo-cells being electrically connected in series with an electrical power supply, a first output terminal connected between said photo-cells, a second output terminal connected to a center tap of said power supply, and an adjustable light mask for adjustably varying the intensity of at least one light beam to establish a base reference for the electrical level across said output terminals for a predetermined equilibrium position of the level of liquid in each of said bores of said pair whereby a deviation of said electrical level from said base reference is an analog representation of the differential change of level of said liquid in said bores.

Claim 7

A sensor comprising a housing, a pair of bores disposed in said housing, a third bore in said housing placing the bores of said pair in communication with each other, a liquid filling said bores to a predetermined common level above said third bore, a light source, means for projecting a beam of light from said light source through each of said bores of said pair from an end thereof, a pair of photo-cells having an electrical resistance varying as a function of the amount of light impinging thereon each disposed at the other end of each of said bores of said pair, said photo-cells being electrically connected in series with an electrical power supply, a first output terminal connected between said photo-cells, a second output terminal connected to a center tap of said power supply, and an adjustable light mask for adjustably varying the intensity of at least one light beam to establish a base reference for the electrical level across said output terminals for a predetermined equilibrium position of the level of liquid in each of said bores of said pair whereby a deviation of said electrical level from said base reference is an analog representation of the differential change of level of said liquid in said bores.

Claim 8

The sensor of claim 5 wherein said light source is disposed in a block of light transmissive material obturating said bores of said pair at the first mentioned end thereof.

Claim 9

The sensor of claim 5 further comprising venting means for venting each of said bores of said pair to ambient disposed above the level of the liquid in said bores.

Claim 10

The sensor of claim 5 wherein said photo-cells are photo-resistors.

Claim 11

The sensor of claim 5 wherein said photo-cells are photo-conductors.

Claim 12

The sensor of claim 6 wherein said light mask is a light absorbing threaded member threadably disposed in said block of light transmissive material in the path of one of said light beams.