The study on Ladar fiber optical liquid level sensor system

A novel fiber-optic liquid level sensor of Laser radar is reported in this paper. Using the absolute technique of Ladar in which the phase of amplitude modulated lightwave reflected from the liquid face is compared with that of the original modulate signal;the liquid level can be measured precisely. A special symmetric compensating optical system,which has a common axis for light emitting and receiving, is proposed to eliminate many adverse effects. Separating and connecting its electric part and optical part by optical fiber cable,the one-time electronic-free optical measurement has been realized on a simulated oil tank and an accuracy of +/- 0.3% is achieved within a temperature range of 20 degrees similar to 40 degrees C over a measuring range of 0 similar to 6m.