An electromagnetic method of measurement of density or specific gravity of liquids

Abstract

The instrument described determines the specific gravity of liquids by measuring the minimum electromagnetic force in terms of current required to attract an immersed float through a fixed distance. The float contains a soft iron armature and its specific gravity is arranged to be either slightly greater or less than the extremes in the range of specific gravity required to be measured, according to whether the float is attracted upwards or downwards through the liquid. The method permits remote indication or recording by a conventional moving coil meter or pen chart recorder if the motion of the float is arranged to actuate a signal such as the completion of an electrical circuit. A simple manually operated form for non-electrolytes of low viscosity is described; the method is, however, capable of extension to other liquids and could be made to operate automatically on a cyclic basis. Fundamentally, the method measures density; the application described is scaled in terms of specific gravity.