Specific gravity is measured by a hydrometer, refractometer, pycnometer or oscillating U-tube electronic meter. The latter included a thermometer, barometer, hydrometer, altimeter and a set of gas analysis instruments. A thermohydrometer is a hydrometer that has a thermometer enclosed in the float section. API gravity is graduated in degrees on a hydrometer instrument. The 18th century Industrial Revolution brought about such innovations as the thermometer and hydrometer. A urinometer is a medical hydrometer designed for urinalysis. A blank (containing only water and the dispersing agent) is used to calibrate the hydrometer. Hydrometer analysis is performed if the grain sizes are too small for sieve analysis. The two traditional methods are sieve analysis and hydrometer analysis. The hydrometer transformed how beer was brewed. Measurements are taken using a soil hydrometer. The relative density of a liquid can be measured using a hydrometer. Using the hydrometer, brewers could calculate the yield from different malts. ASTM provides the detailed procedures for performing the Hydrometer test. It is, of course, necessary that the hydrometer floats in both liquids.