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Red Sea Refractometer

Red Sea Refractometer
Red Sea Refractometer.

Key Features:
• Directly reads the absolute salinity of seawater at 25°C (No need for seawater or temperature compensation factors).
• Easy to read, high resolution display.
• Includes Automatic Temperature Compensation (ATC).

Importance of Salinity:
Maintaining a correct and stable salinity is a fundamental part of successful reef keeping. The importance we place on salinity is clear from the recommended use of our salts and Reef Care supplementing program.

Refraction & Refractometers:
All transparent materials such as liquids refract (distort) light. All transparent materials refract light differently and have what is called a “refractive index” which is a measure of how much a particular material distorts light.
Different concentrations of the same liquid have different refractive indexes. The scale of a refractometer is calculated by using a mathematical algorithm that relates the measured refractive index to the concentration for a specific liquid.

Salinity is a general term describing the concentration of salt in water. However, solutions of different type of salts have different refractive indexes.

Brine is a solution of sodium chloride (table salt) that contains two chemical elements, sodium & chlorine. Seawater contains approximately 70 chemical elements that include calcium, magnesium, potassium etc. in addition to the sodium & chlorine.

Seawater and brine of the same salinity (i.e. the same weight of salt per litre) have different refractive indexes and will give different salinity readings if measured on the same refractometer.

Absolute Salinity of Seawater:
The PPT scale on Red Sea’s seawater refractometer is calculated using an algorithm for seawater and therefore will give a reading of the Absolute Salinity of seawater. The PPT scale on regular salinity refractometers are calculated using an algorithm for brine. Using a brine refractometer for seawater will give an error of approximately 1.5ppt in the salinity reading.

Calibrated at 25°C – no compensation factors required:
The refractive index of liquids change with temperature and therefore has a major effect on measuring salinity with a refractometer. The algorithm for defining the PPT (and S.G.) scale for a refractometer is calculated for a specific temperature.

PPT readings from refractometers that are not calibrated for reef aquariums (i.e. 25°C) need to be adjusted according to a conversion table to give the actual PPT at the aquarium temperature. This is often a cause for misinterpretation of refractometer readings. For example, using a seawater refractometer calibrated at 20°C will give a PPT reading that is approximately 1-1.5ppt lower than the absolute salinity of the same water sample at the normal aquarium temperature of 25°C.

ATC - Automatic temperature compensation:
Temperature is probably the biggest cause of incorrect readings with a refractometer. Calibration and testing of water samples should be done after the refractometer and water sample have equalized at the correct temperature.

Automatic temperature compensation (ATC) compensates for a few degrees of difference between the ambient temperature and the calibrated temperature of the refractometer. Larger temperature variations will give an error of approximately 1.0ppt in the salinity reading.
ATC does not adjust the PPT reading of a refractometer to the temperature of the aquarium.

Easy to read, high resolution display:
The quality of the optics gives a sharp blue/white division making it easy to get a clear and accurate reading of the salinity. The scale is appropriate for reef aquariums, making it easier to read than standard refractometers.

A practical example:
Using a seawater refractometer calibrated at 20°C will give a PPT reading that is approximately 1-1.5ppt lower than the absolute salinity of the same water when it is at the normal aquarium temperature of 25°C. This represents an error of approximately 3% for an aquarium maintained at 35ppt.

Using the reading of a refractometer calibrated at 20°C without adding a temperature compensation factor will therefor cause you to believe that your salinity is lower than you want. To raise the salinity of the water you will then add another 3% of your salt mix to the water, unnecessarily increasing the cost of the salt that you use and more importantly, increasing the salinity to over 36ppt.

Red Sea’s “Reef-Spec” Seawater Refractometer gives a direct reading of the absolute salinity without need for any compensation factors.
SKU 7290100774830
Quantity in stock 5 item(s) available
Weight 1.00 kgs
mpn R12018
product type Aquatic Equipment
Our price: £39.99
Quantity (5 available)
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