Measuring salinity of marine aquariums does not get any easier OR faster than this! Now professional measurement is as simple as dripping sample water onto the prism surface and pressing the READ key. In less than 2 seconds, this outstanding precision device will display the results in clear, digital numbers on the LCD screen. Dual-level LCD shows measurements in Practical Salinity Units (PSU), Salinity in Parts Per Thousands (PPT) or Specific Gravity S.G. (20/20). Automatically compensates for temperature for accurate research-grade analysis. Rugged, water-resistant unit boasts compact design and operates on a 9V battery (included) for wire-free portability. Features low battery-life indicator and shuts off automatically after 3 minutes of non-use to preserve battery life. Digital Seawater Refractometer measures only 7-1/2" x 4" x 2-5/8" high.
Please click on "More Information" for calibration and measurement procedure.
Calibration should be performed daily, before measurements are made, when the battery has been replaced, between a long series of measurements, or if environmental changes have occurred since the last calibration.
To Change Measurement Unit
To Change Temperature Unit
Designed for Research Grade Analysis
The Seawater Digital Refractometer is an optical device that is quick and easy to use. After a simple user calibration with distilled or deionized water, a seawater sample can be introduced into the sample well. Within seconds, the refractive index and temperature are measured and converted into one of three popular measurement units: Practical Salinity Units (PSU), Salinity in Parts Per Thousand (PPT), or Specific Gravity (S.G. (20/20)). All conversion algorithms are based upon respected scientific publications using the physical properties of seawater (not sodium chloride). Temperature (in degrees Celsius or Fahrenheit) is displayed simultaneously with the measurement on the large dual level display along with icons for Low Power and other helpful message codes.
Key Features Include:
Temperature Compensation: Automatic between 0 and 40 degrees Celsius (32-104 Fahrenheit)
Principle of Operation
In the Seawater Digital Refractometer, light from an LED passes through a prism in contact with the sample. An image sensor determines the critical angle at which the light is no longer refracted through the sample. Specialized algorithms then apply temperature compensation to the measurement and convert the refractive index to: PSU, PPT or S.G. (20/20). PSU is defined as a definitive salinity-conductivity ratio relationship. It is based upon the work of the UNESCO, ICES, SCOR and IAPSO. This information is published in The Joint Panel of Oceanographic Tables and Standards. PPT (10-3) is an older used salinity scale where salinity is defined by "the salt content is the weight of the inorganic salts contained in 1 kg of seawater if all bromide and iodide are replaced by an equivalent amount of oxides" (Knudsen, 1901). Specific Gravity (20/20) is based upon the published relationship between density at 20 °C and the mass of the dissolved salts in the seawater sample (CRC Handbook of Chemistry and Physics, 87th Edition).