Optical distance meter using a pulsed laser diode and fast avalanche photo diodes for measurements of molten steel levels

An optical distance meter with a wide dynamic range, is proposed for measuring the level of molten steel in a steel mold The meter operates by measuring the flight time of a short optical pulse that is propagated between the light source and the target. A pulsed laser diode with a fast rise time is utilized as a light source, and two avalanche photo-diodes are used as detectors. The optical distance meter performs at a measurement range and a standard deviation of the measurement error of 1 m and 1 mm for the black paper larger, respectively. To test its reliability, the distance meter is used to monitor the level of molten steel during a continuous casting process. The results obtained were compared with those obtained using an eddy current sensor and a gamma-ray sensor. The measurement range of the optical method is ten times those attained using other two sensors. Continuous monitoring of the steel level call be done from the initiation of the casting process with the proposed distance meter.