A hydrometer is an instrument which is most commonly used for testing the density of a liquid in relation to water. Hydrometers are used in many different sectors and industries as well as being a popular instrument that can be used in the home. They are usually made of glass and consist of a cylindrical stem with a printed scale and a bulb weighted to make it float upright. The correct scale reading is that corresponding to the plane of intersection of the of the horizontal liquid surface and the stem. For instructions and video on how to use a hydrometer please see our previous blog here.
Hydrometers vary in many ways; measurement range, length, material as well as scale increments. Below we explain three main unit measurement options; specific gravity, twaddle and baume.
The traditional hydrometry scale is Specific Gravity (density, relative to that of water at 60°F) used in the 1960 edition of the British Standard 718. This is still much in demand and general purpose hydrometers will use this scale. The specific gravity 60/60°F scale compares the relative density of a given liquid with that of water, at 60°F (15.6°C).
The Twaddle scale is a simplified scale based on specific gravity where 0° Twaddle equates to SG60/60°F of 1.00 (that of water) and each degree Twaddle equals 0.005° SG. Our range of Twaddle hydrometers are available in 2 lengths, 160mm or 300mm, each with single degree divisions and are adjusted for use at 15.6°C (60°F) for medium surface tension liquids.
Baumé hydrometers are for liquids heavier than water. Zero degrees Baumé equates to an SG 60/60°F of 1.00. The Baumé of distilled water is 0. This scale uses the accepted relationship for degrees Baumé where: Liquids heavier than water SG= 145/(145-°Be).
Our range of Baumé hydrometers are all 250mm long and are adjusted at 15.6°C (60°F) and suitable for medium surface tension liquids.
If a UKAS certification, certificate traceable to Recognised National Standard or Statement of Conformity is required with your chosen hydrometer please get in touch for the full options.
For more information on choosing the correct hydrometer for your application please get in touch with one of our technical team on 01954 233 120, email firstname.lastname@example.org or fill in the below form