Atago 2491 MASTER-S/Millα, Salinity Refractometer, MASTER Series, Salinity : 0 to 100‰ , Specific Gravity : 1.000 to 1.070 Measurement Range

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Ultimate Functionality , Unsurpassed Quality, Seamless Usability 

This instrument measures the salinity and specific gravity of seawater, and utilizes a new material that is durable against salty samples, The salinity of seawater is displayed in parts per mill (‰). It is an Automatic Temperature Compensation (ATC) model with water resistant properties (IP65).

Specific gravity
Measurement RangeSalinity : 0 to 100‰
Specific gravity : 1.000 to 1.070
(Automatic Temperature Compensation)
Minimum ScaleSalinity : 1‰
Specific gravity : 0.001
Measurement AccuracySalinity : ±2‰
Specific gravity : ±0.001
(10 to 30゚C)
RepeatabilitySalinity : ±1‰
Specific gravity : ±0.0005
International Protection ClassIP65 (except eye piece)
Dust-tight and Protected against water jets.
Dimensions & Weight3.2 x 3.4 x 20.7cm, 110g
  • Milky White Daylight Plate : RE-2471-65M

Design Registration No.000379326-0001, 000379326-0002 (EU)
ZL 2005 3 0116403.4,5 (China), D111526 (Taiwan), D555, 549 (U.S.A.),
1255763, 1255764, 1255765, 1255766, 1255767 (Japan)
Patent Granted in countries around the world.

  • £256.00
  • £320.00
    • SALE!

Product Line-Up

Reason to choose MASTER series

Water resistant(α & H series)

Water resistant

"Washable". A special design concept for analog type measuring instruments. It is a new mechanism that can be washed even under running water after measurement.



The readability of measured values is the "lifeline" for hand-held refractometer.Not only the brightness of the entire field of view, but also the clarity of the boundaries represents the basis of the optical technology that ATAGO has reached.

Contamination free

Contamination free

Uses a smooth grip with no irregularities. The carbon-like design contributes to both cleanliness and playfulness.

ATC Temperature compensation(α・H・T series)

The measured value are automatically corrected according to the environment. We have thoroughly improved the structure and arrived at a mechanism, patented that is not found anywhere else.

Function and Design


Measurement Method

    • SKU
    • UPC/ISBN
    • Commodity Codes
  • Measurement Range
    Salinity : 0 to 100‰, Specific Gravity : 1.000 to 1.070
  • Measurement Accuracy
    Salinity : ±2‰, Specific Gravity : ±0.001
  • Body Material
    Plastic body : PBT (Polybutylene terephthalate), resistant to salty and acidic samples
  • Other Features
    α : Water resistant (IP65)
  • Use
    Salinity, Specific Gravity of Seawater
  • International Protection Class
  • Manufacturer
    Atago Co Ltd
  • Country of Origin

Always have a constant taste!

Seasoning / soy sauce / sauce / soy milk / Sauce / jam / honey / bean paste syrup / oil / fat etc.

Active in quality stability!!

Fruit drink / soft drink Carbonated drinks

Eating out When stewed To check the end point!

Ramen soup / Mentsuyu Sauce / bowl sauce, etc.

To determine the harvest time!

Fruit / vegetable / leaf juice Stem juice / root juice

Pickling liquid and seawater For concentration check!

Saline / seawater / pickle preparation liquid 
Metal Processing
Of cutting oil For concentration control!

Chemical Of various solutions For refractive index management!

Cleaning solution / antifreeze solution / brine solution Snow melting agent / cosmetics

Urine specific gravity, serum protein For inspection!

Urine / serum
※There is also a scale for clinical use.