Development of an Ultrasonic Technique to Measure Specific Gravity in Lead-Acid Battery Electrolyte

An ultrasonic technique to measure specific gravity in lead- acid battery electrolyte is described in detail. This technique, which is based on the theory that the velocity of sound in a liquid depends on the density of the liquid, compares the ultrasonically measured velocity of sound in battery electrolyte (derived by measuring the time required for sound to traverse a known distance of electrolyte) to velocities in a computerstored data base relating velocity, density, and temperature. The experimental design, the data base developed for the method, a laboratory feasibility study, and an error analysis of the study are dis- cussed. The major advantages of the method are 1) the passive nature of the measurement, 2) the continuous sample and display capabilities, 3) the instantaneous tracking of changes in specific gravity, and 4) in- herent averaging of the specific gravity measurements.