Hydrometer Calibrations
16010C

NIST provides measurement services for reference hydrometers to measure liquid density. These reference standard hydrometers are generally used as laboratory standards to calibrate other hydrometers.

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. The hydrometer scale should be divided into 0.001, 0.0005, 0.0002, or 0.0001 units of specific gravity. Proof spirit hydrometers cover the range of 0 to 200 proof. The alcohol hydrometer scale should be divided in whole, half, fifth or tenth percents.  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. The calibration at NIST consists of comparing NIST master hydrometers directly with the customer's hydrometers in a liquid of low surface tension.

The cost of a typical calibration is $1,506 per hydrometer. We deliver a calibration report per item tested that includes an uncertainty analysis.  The expanded uncertainty for NIST master hydrometers depends on stem scale. Components of the expanded uncertainty include the Type A Standard Uncertainty, composed of the imprecisions of such process components as scale readings, thermal gradient of the calibration fluid, etc., and Type B Standard Uncertainty, based on direct comparisons to solid density standards (plummets), density of water, and precision mass standards. To read more about our procedures and uncertainties see our Technical Notes and Publications.

Turnaround time for a single hydrometer is approximately 3 weeks:

  1. Allow 2 weeks for shipping;
  2. 1 week for set-up, data collection, report writing and review.

However, please contact Sherry Sheckels to schedule the calibration of your instrument(s).

To have your hydrometers calibrated:

  1. Contact Sherry Sheckels to schedule your calibration dates;
  2. Fax or mail a purchase order to Sherry Sheckels following purchase order guidelines and choosing a Service ID Number of 16010C (we also accept credit card orders), and
  3. Ship your hydrometers to Sherry Sheckels following shipping procedures outlined in the NIST Calibrations User's Guide SP 250.

 

Sherry D. Sheckels
National Institute of Standards and Technology 
Fluid Flow Group 
100 Bureau Drive, Stop 8361 
Gaithersburg, MD  20899-8361 
Phone:  301-975-5940 
Fax:  301-258-9201
Email:  sherry.sheckels@nist.gov

John D. Wright
National Institute of Standards and Technology 
Fluid Flow Group 
100 Bureau Drive, Stop 8361 
Gaithersburg, MD  20899-8361 
Phone:  301-975-5937
Fax:  301-258-9201 
Email: john.wright@nist.gov