The Robinson Thermohydrometers precision grade design meets API oil testing specifications and is calibrated to API scale Modulus 141.5 at 60F. The hydrometers are constructed with a solid alloy ballast and are designed to permit quick penetration to the setting point, creating no air bubbles. Each hydrometer incorporates a built-in thermometer for convenience when testing samples.

All hydrometers can be certified upon request. Thermohydrometers are certified at three points on the gravity scale as specified by NIST (formerly NBS). Each certified instrument is accompanied by a document of certification that includes the correction of each point tested.