The Optical Velocity sensor (OVM) is a rugged, stand alone, non-contact device, designed to measure velocities of off-gas in hostile environments. The velocity of a gas as it exists a process is vital information for many industrial applications. The presence of laminar flow is a requirement for this device. Turbulent flow introduces noise which effects the accuracy of the measurement.

The Optical Measurement System uses light emitted by the furnace gas to measure velocity. As dust and hot gases flow past the upstream sight tube, light is collected by a lens and transferred by fiber to a cabinet. In the cabinet the light is converted into an electrical signal and recorded on a computer. The same dust and hot gases flow past the second sight tube producing a similar electrical signal.

The signals are cross correlated to determine the time of flight between the first and second sight tube. A velocity is calculated from the time of flight and passed to the plant control system. The system consists of an optical assembly mounted on the furnace duct, a purge box and a cabinet located away from the furnace duct.