position of a permanent magnet whose displacement is sensed by a concentric array of Hall-effect linear displacement sensors. The output signals of the sensors are mixed in a dedicated electronics module that provides a single output voltage whose magnitude is a direct linear measure of the quantity to be measured. The relative density in soil mechanics The relative density a measure of the current void ratio in relation to the maximum and minimum void rations, and applied effective stress control the mechanical behavior of cohesionless soil. Relative density is defined by in which , and are the maximum, minimum and actual void rations. Examples Substances with a relative density of 1 are neutrally buoyant, those with RD greater than one are denser than water, and so (ignoring surface tension effects) will sink in it, and those with an RD of less than one are less dense than water, and so will float. Example: Helium gas has a density of 0.164 g/L; it is 0.139 times as dense as air, which has a density of 1.18 g/L. Urine normally has a specific gravity between 1.003 and 1.030. The Urine Specific Gravity diagnostic test is used to evaluate renal concentration ability for assessment of the urinary system. Low concentration may indicate diabetes insipidus, while high concentration may indicate albuminuria or glycosuria. Blood normally has a specific gravity of approximately 1.060. Vodka 80° proof (40% v/v) has a specific gravity of 0.9498. See also API gravity Baumé scale Buoyancy Fluid mechanics Gravity (beer) Hydrometer Jolly balance Plato scale References Further reading Fundamentals of Fluid Mechanics Wiley, B.R. Munson, D.F. Young & T.H. Okishi Introduction to Fluid Mechanics Fourth Edition, Wiley, SI Version, R.W. Fox & A.T. McDonald Thermodynamics: An Engineering Approach Second Edition, McGraw-Hill, International Edition, Y.A. Cengel & M.A. Boles External links Specific Gravity Weights Of Materials Density Physical quantities Ratios