General Specifications for Bellwether ASTM Hydrometers: Manufactured in strict
accordance to specifications of ASTM (American Society for Testing and Materials) for
accuracy and design. All instruments are suitable for certification for use as a primary
reference standard with NIST traceability.
Specific Gravity, also known as relative density, is the ratio of the mass of a solid or liquid
to the mass of an equal volume of distilled water. The standard temperature of calibration
in the U .S. is 60°F/ 60°F.
General Specifications for Bellwether ASTM Hydrometers: Manufactured in strict
accordance to specifications of ASTM (American Society for Testing and Materials) for
accuracy and design. All instruments are suitable for certification for use as a primary
reference standard with NIST traceability.