Cryogenic fluids density reference system: Provisional accuracy statement (1980)

An improved Density Reference System, reference densimeter, and method of determining sample density are described. The uncertainty of the density reference system is + or -0.055 percent. The contribution from the estimated systematic error in density was + or -0.022 percent. The estimated uncertainty caused by random error is three times the standard deviation of 0.011 percent and is based on measurements of densities of saturated liquid methane. Total density uncertainty is the sum of the systematic and random errors for a density range of 400 to 480 kg/cu m at pressures from 0.8 to 4 bar absolute and temperatures between 109 and 128 K. This accuracy statement is expected to apply over ranges of at least 400 to 1000 kg/cu m in density, 77 to 300 K in temperature and 0.8 to 7 bar in pressure. This system has great accuracy, speed, reliability, and flexibility.