VEE GEE API Scale Hydrometers measure the scale which was selected in 1921 by the American Petroleum Institute (API), the U.S. Bureau of Mines, and the National Institute of Standards and Technology (NIST) as the standard hydrometer scale for petroleum products. The API Scale is based on the following formula:
The Thermometer Scale (where applicable) for VEE GEE Hydrometers with Thermometers is located in the body. General Specifications for VEE GEE ASTM Hydrometers (where applicable): 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 with NIST traceability.