THE REEF SEA METER - NATURAL SEA WATER REFRACTOMETER
Specifically designed for aquarium use for measuring the salinity of Natural Sea Water (NSW)
Specifications:
Range: Minimum Division: Accuracy: Light Source:
0-40 Parts per Thousand of Salinity in NSW 1.00 PPT +/- 1.00 PPT Ambient: Sunlight or Lamp
1.015 to 1.030 Specific Gravity 0.001 SG +/- 0.001 SG
Almost all hand held salt water refractometers available to the hobby are designed and calibrated for the testing of brine solutions, i.e. sodium chloride, and are not calibrated for the refractive index of Natural Sea Water. This is a very important distinction. Other Salinity Refractometers used for marine aquariums are designed to test salt in water – nothing else! The Reef Sea Meter is designed to measure Salinity of Natural Sea Water taking into account the other elements that comprise salinity in the marine water sampled.
Even though the largest percentage of salt in the sea is sodium chloride, the presence of other significant ions such as magnesium and calcium in natural sea water results in a different refractive index relative to that of brine. A standard salt (brine) refractometer will therefore not give the correct salinity for Natural Sea Water and a conversion factor must be applied.
For example a 35ppt solution of NSW has the same refractive index as a 36.5ppt solution of brine. When using a normal brine Refractometer the user should therefore look for a reading of 36.5ppt when trying to achieve a reading of 35ppt for Natural Sea Water.
EASIER TO READ – MUCH EASIER TO READ!
One of the other problems with most Refractometers is that the scale displayed normally reads from 0-100ppt when we are really only interested in the region from 30-40ppt.
Our The Reef Sea Meter Refractometer has therefore been specifically designed to read from 0-40ppt which gives you 2.5 times the resolution of a normal 0-100 scale.
AUTO TEMPERATURE COMPENSATION (ATC)
Salinity is a measurement of a mass of salt in a mass of water and therefore does not vary with temperature however a Refractometer does not measure salinity directly but measures the refractive index which is then displayed as salinity. The refractive index of a solution does vary with temperature therefore the reading that you measure with a Refractometer is always temperature dependant.
What people do not generally understand is that it is the temperature of the instrument and not the water temperature that is important as the small sample of water used for testing will equilibrate within seconds to the temperature of the Refractometer.
Once correctly calibrated at the set calibration temperature of 20’C/68’F the Refractometer can then be used in environments where the ambient temperature and therefore instrument temperature would heat up or cool down within the range of the ATC which is between 10-30’C/50-86’F.
CALIBRATION
If you look at the scale above you will see that the Refractometer states that it is calibrated at and displays the SG of seawater at 20’C (68’F). Most salt Refractometers use this temperature and will be marked 20’C (68’F) or 20/20.
Calibration should always be carried out with the instrument at 20’C/68’F which is close to the average room temperature in most cases. Allow the Refractometer to stand at this temperature for 30 minutes to acclimate. This allows for the best calibration possible.
The Reef Sea Meter Refractometer is designed with a copper body which is more expensive to manufacture but responds faster to ambient temperature changes than other materials.
PLEASE DO NOT CALIBRATE WITH 35PPT SALINITY SOLUTIONS AS THEY ARE NOT THE SAME AS NATURAL SEA WATER!
MEASURING THE SALINITY OF YOUR AQUARIUM
Ensure that the prism of your Refractometer is clean by washing the prism plate and cover plate after use each time in pure water and drying it with the polishing cloth supplied. Why? The prevent corrosion of the unit and to ensure that your readings are accurate.
Take a representative sample of the water from your aquarium or other marine habitat.
Allow the water to acclimate to the temperature of the instrument for 15 seconds and then look down the eyepiece to take the salinity reading at the bottom of the blue and clear interface.
One side of the scale will allow you to read the salinity and the other side the specific gravity calculated at 20’C/68’F.
The Reef Sea Meter Refractometers are calibrated at 20’C/68’F and so the calculated specific gravity at 35ppt displays a reading of 1.0266. This is the equivalent to a specific gravity reading of 1.0264 for a water sample temperature of 25’C/77’F using a standard hydrometer that has a calibration temperature of 25’C/77’F
Included are: A plastic, foam-lined hard case, a pipette for dropping test fluids onto the prism (never dip the refractometer into the test fluid!), a mini screwdriver for scale calibration, and a Users Guide.
Other types of Portable Refractometers are available through our www.bulkrefractometers.com Store!
National Industrial Supply
32483 Temecula Parkway, #E112
Temecula, CA 92592, USA
Sales: 310.748.6858
Fax: 310.733.5480
E-mail: chardowner@yahoo.com
