An Automatic Diver Balance

Abstract

1. An automatic, electromagnetic diver balance is described. 2. The working principle of this instrument is that a small plastic cylinder, the diver, with density less than one is kept floating in an aqueous medium by a magnetic force acting on a permanent magnet enclosed in the diver. In the floating position the diver cuts off a light beam which, through an electronic system, controls the magnetic force acting upon the diver. The latter will move down until its buoyancy is compensated by this force. 3. With this balance one may register the submerged--or reduced--weight of any object placed on the floating diver. 4. The apparatus has hitherto found application in water-permeation studies (D2O-H2O exchange) and in determinations of the cortical tension in the frog's egg. Potentially the instrument may be used for various other purposes, notably for manometric determinations.