The Pro-1 Normal Seawater Refractometer of Tropic Eden is an optical device that employs the refraction of light through transparent media to determine the salinity and specific gravity of natural or artificial seawater, oceanic water, and brackish water intermediate. The straight forward and unchanging optical properties of light refraction is simple and direct, yet gives clear, unambiguous and very reliable measurement. The Pro-1 Normal Seawater Refractometer is meticulously designed according to the optical properties of normal seawater, based on the proportional sum function of the refractive index (RI) of all 70+ major, minor and trace elements, further taking into account temperature factor and the mean of natural seawater samples obtained from more than 120 locations in the sea and coral reefs around the world. The Pro-1 is highly precise and well built with special high density alloy for immediate heat conduction and crisp high quality lens, which is quick and easy to use for laboratories, seawater marine aquariums, or research out in the field.
Principle of Operation
A refractometer determines the salt content of a medium based on its refractive index (RI). It works on the principle that light travels slower in media with higher RI. As a result of that optical property, light bends when it travels between two media with different RI, and beyond the critical angle, light simply reflects off the interface between the two media without refracting into the other medium. A refractometer works by passing light through a sample medium into a prism and by determining the critical angle which is unique to the particular medium. Governed by the critical angle, light exiting the prism falls only on one side of a dividing line and never on the other side. The dividing line between the two sides parts the upper blue part and the lower white part on the scale, which is designed to mark the salinity (ppt/psu) and specific gravity (s.g.) of the medium being tested.
In addition, at normal temperature range of seawater in most parts of the world, the RI and specific gravity of seawater increases at lower temperature. The Pro-1 Normal Seawater Refractometer is designed to precisely compensate that temperature factor with a built-in automatic device. And very importantly, unlike refractometers tailored only on sodium chloride at 68°F/20°C or designed solely on theoretical principles, the Pro-1 is designed for seawater at 78.8°F/26°C (coral reef) based on the proportional sum function of RI of all 70+ major, minor and trace elements of natural seawater sampled from more than 120 locations in the sea and coral reefs around the world.
Step 1. To ensure sharp and accurate reading, clean the prism and the prism cover from any dirt or salt residue with pure or reverse
osmosis water. Wipe dry.
Step 2. Fill and empty the pipette dropper (the one with rubber ring) a few times with the seawater to be tested to eliminate any contaminant mixed into the sample.
Step 3. Hold the refractometer horizontally and lift up the sample cover, place 3-4 drops of seawater sample onto the prism surface. Lower the sample cover onto the prism with no noticeable air entrapped under the cover.
Step 4. Wait for about 20-30 seconds for the temperature of the sample and the refractometer to equilibrate.
Step 5. Point the refractometer to a bright light source (sunlight or artificial white), and look into the eyepiece while turning it to focus.
Step 6. On the scale, the sharp dividing line between the upper blue part and the lower white part is where the salinity and specific gravity reading is. (If the dividing line appears a little fuzzy, clean the prism surface and cover and start over.)
Step 7. When finished, clean the prism surface, prism cover and anywhere of the refractometer that has touched seawater with clean freshwater. Keep the refractometer dry in the case or the pouch supplied.
The unit is factory calibrated. To recalibrate, repeat the above steps at 78.8°F/26°C with pure or reverse osmosis water using the pipette dropper (the one without rubber ring). In most cases the dividing line should not be far off from zero if at all. If needed, turn the calibration knob with the calibration key to bring the dividing line to zero. Alternatively, recalibration may be done with 35ppt seawater and the dividing line be set at 35ppt/1.02633 at 78.8°°F/26°°C.
Type: Full Spectrum Seawater
Division: 0.1% ppt / s.g. 0.001 Accuracy: +/-0.2%
Weight of Unit: 260grams
Scale Range: 0-45ppt (full spectrum seawater), 1.000-1.035 S.G.@78.8°F/26°C
Dimension of Unit: 30x30x185mm
Temperature Range: Automatic Temperature Compensation 59-113°F/15-45°C
- Handle the refractometer with care.
- Avoid scratching the prism surface with sharp objects.
- Store in dry and cool place after use.
Each unit is supplied with:
- Pro-1 Standard Normal Seawater Refractometer
- Two pipettes
- Calibration key
- Euser manual
- Calibration fluid 0ppt, 35ppt not included and may be purchased separately.