An Automatic Surface Follower for Measuring the Rate of Evaporation of Molten Metals Undergoing Vacuum Distillation

Abstract

The automatic surface follower was developed to measure continuously the rate of evaporation of molten zinc at low pressure and to measure temperature gradients near the evaporating surface. The follower consists of a motor driven electrode that moves downward continuously until it contacts the metal surface and actuates a relay which stops the driving mechanism. Evaporation of metal lowers the surface level and breaks contact with the electrode thus causing the electrode to follow the level as evaporation proceeds. A record of the level displacement is recorded on a strip-chart potentiometer as a voltage, proportional to the movement of the electrode from which the rate of evaporation can be derived as a continuous function. A thermocouple mounted on an auxillary carriage which can be moved independently of the electrode may also be used to explore the temperature distribution above or below the surface, while the electrode automatically establishes the location of the surface as a reference point.