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Liquid Density Hydrometer Calibrations
NIST calibrates hydrometers for measuring liquid density using a gravimetric method (Cuckow's method) with uncertainty of 0.01% (k = 2). Customer submitted reference standard hydrometers are generally used as laboratory standards to calibrate other hydrometers. To read more about our facilities, see the NIST Special Publication 250-78.
Reference hydrometers accepted for calibration include specific gravity, proof spirit for alcohol solutions, API degrees for petroleum measurements, degrees Baume heavy and degrees Baume light, and other arbitrary scales, all subject to discussion with the technical contacts listed below. Specific gravity hydrometers cover the specific gravity range of 0.65 to 2. Proof spirit hydrometers cover the range of 0 to 200 proof. Reference hydrometers should be made of smooth, transparent glass, free of bubbles or other imperfections. The hydrometer should bear an inscription which indicates the purpose of the instrument. This inscription should denote the reference temperature at which it is to be used. The maker's name or trade mark and an identification number should be inscribed on the hydrometer scale.
Visual inspection should be made by the customer before shipping to NIST for calibration. The hydrometer should be packed in a safe reusable shipping container.
NIST will provide a three-point calibration on these reference hydrometers. Additional points can be provided at an additional charge if requested.
We deliver a calibration report per item tested that includes an uncertainty analysis.
Calibration fees for this and other services can be found in the Fee Schedule available online from the NIST Calibrations Website.
To have your hydrometers calibrated: