รหัสสินค้า : HB001
Hydrometer - Introduction
The traditional hydrometry scale of Specific Gravity (density, relative to that of water at 60°F) used in the 1960 edition of the British Standard 718 is still much in demand and the General Purpose hydrometers use this scale.
For the Specification Density Hydrometers to BS 718 : 1991, the internationally accepted basis of scale is grams per millilitre (g/ml) with a reference temperature of 20°C (or, exceptionally 15°C). For use in tropical countries, ISO 387 proposes that hydrometers be adjusted at a higher reference temperature, 27°C (as opposed to the previously used high adjustment of 84°F).
Instruments adjusted at this higher temperature can be supplied to special order. In addition to being adjusted for use at a specific reference temperature, hydrometers are adjusted with regard to the Surface Tension of the materials whose density is to be determined. Surface tension may be expressed specifically for example 55 mN/m (millinewtons per metre) or described as a band. Low surface tension is less than 35 mN/m and medium surface tension is between 35 and 55 mN/m.
General Purpose Specific Gravity Hydrometer
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The instruments listed are similar to hydrometers included in ISO 650 and in the (now superseded) 1960 issue of British Standard 718.
All hydrometers can be supplied with UKAS certification, certificate traceable to Recognised National Standard or Statement of Conformity, if required.
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. These 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.
The Baumé hydrometers listed are for liquids heavier than water. Zero degrees Baumé equates to an SG 60/60°F of 1.00.
This scale uses the accepted relationship for degrees Baumé where: