Atago 2991 MASTER-20Pα Hand-Held Refractometers MASTER Series, Plastic Body, Water Resistant IP65, Brix : 0.0 to 20.0% Measurement Range

Not rated yet



  • Soft Drink
  • Soup
  • Fruits & Vegetables
  • Cutting Oil 
  • Cleaning Agent etc
Measurement RangeBrix : 0.0 to 20.0% (Automatic Temperature Compensation)
Minimum ScaleBrix : 0.1%
Measurement AccuracyBrix : ±0.2% (10 to 30゚C)
RepeatabilityBrix : ±0.1%
International Protection ClassIP65 (except eye piece)
Dust-tight and Protected against water jets.
Dimensions & Weight3.2×3.4×20.7cm, 110g


· 10% Sucrose (±0.03%) : RE-110010

· 20% Sucrose (±0.03%) : RE-110020

· Daylight plate for small volume samplings : RE-2391-50M

* Calibration Certificate : Contact an ATAGO representative for details.


· Daylight plate : RE-2315-61M


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.

Call 01463 830401 For Any Assistance
Compact and easy to carryAutomatic Temperature Compensation

MASTER-20Pα are low concentration model (measurement range Brix 0.0 to 20.0%) of the MASTER-α / MASTER-Pα. Good for measurements of low concentration fruit juices, cutting oil, etc. Automatic Temperature Compensation (ATC) model with water resistant feature (IP65).

The MASTER-20α is made of metal, and the MASTER-20Pα is plastic. The specifications are exactly the same. For salty and acidic samples, choose the plastic body, MASTER-20Pα.
*Verification with the 10% Sucrose Solution (RE-110010) or 20% Sucrose Solution (RE-110020).



How to choose suitable model?


⒈ Please select category, suitable samples or measurement range from the list of MASTER series
⒉ If you are not sure the range of your sample, please refer to our data book


Please select the material

⒈ Metal body : Die-cast aluminum, Ideal for the agriculture industry, metal working fluids and various high-temperature samples
⒉ Plastic body : PBT (Polybutylene terephthalate), resistant to salty and acidic samples


Please select features
  • α : Water resistant (IP65)
  • T : Automatic temperature compensation (ATC)
  • M : Low cost model without the above function
  • S : Suitable for Milky sample
Protection class of the MASTER-α, H series are IP65. You can rinse off the sample by running water on the prism. The design allows the user to easily wipe off the sample.Sample size 2-3 drops.
The Automatic Temperature Compensation function of the MASTER-α, T, H series enables you to take measurement readings regardless of the ambient temperature.Automatic Sample Distribution (ASD)
New prism housing design allows for sample to cover the prism without having to lift the day-light plate! This design will allow for fast & easy measurements.
Convenient Storage case.  


The MASTER series has been improved with a clearer, brighter field of view and made even easier to carry.

Compact Redesign of the MASTER Series (from October 2014)
The MASTER series has been improved with a clearer, brighter field of view and made even easier to carry.
These improvements in our newly compact redesigned models are especially clear when taking measurements in dim lighting, or measuring darkly-colored samples. Even when measuring milky-colored, opaque, or oily samples, the boundary line remains crisp and clear.
Note: The size of the scale has changed. It may take some time to re-adjust to the new field of view when reading measurements.


Icons, for functions, specifications and scales have been added to this catalog

Can be connected to a recorderCan be connected to a recorderMeasurement at a set temperatureMeasurement at a set temperature
Can be connected to a printerCan be connected to a printerAutomatic Temperature CompensationAutomatic Temperature Compensation
Alarm output for high- and low-limit valuesAlarm output for high- and low-limit valuesCan be connected to a circulating Can be connected to a circulating
RS-232C InterfaceRS-232C InterfaceContinuous measurementContinuous measurement
In-line measurementIn-line measurementHigh temperature samplesHigh temperature samples
User scales can be inputtedUser scales can be inputtedExternal Light InterferenceExternal Light Interference

Calibration with waterCalibration with waterClinical refractometersClinical refractometers
Calibration with exclusive standard liquidCalibration with exclusive standard liquidRefractive index scaleRefractive index scale
Compact and easy to carryCompact and easy to carrySalt concentration scaleSalt concentration scale
Digital displayDigital displaySeawater scaleSeawater scale
AC outlet (AC100 to 240V)AC outlet (AC100 to 240V)Wine scaleWine scale
Battery operatedBattery operated  
    • SKU
    • Commodity Codes
  • Measurement Range
    Brix : 0.0 to 20.0%
  • Measurement Accuracy
    Brix : ±0.2%
  • Body Material
    Plastic body : PBT (Polybutylene terephthalate), resistant to salty and acidic samples
  • Other Features
    α : Water resistant (IP65)
  • Manufacturer
    Atago Co Ltd
  • Country of Origin


The name "MASTER" says it all. The MASTER series integrates 76 years of manufacturing expertise into these state-of-the-art instruments. The researchers at ATAGO have addressed the requests of users in 154 countries around the world, and the MASTER series is the embodiment of this extensive research and development. The MASTER series rates 100% in fulfilling both user expectation and illustrating ATAGO's researchers' desire to design the best hand-held refractometer possible.

1. Water Resistant

The concept of a washable hand-held analog unit is exceptional. After measuring, you can clean it with running water under a faucet. The new structural-design of these units allows them to be washed whenever necessary. The MASTER Series is the epitome of user friendliness.

2. Visibility

Efficiently using an analog unit depends on how easily the measured value can be read. With extensive research and the utilization of quality optics, the result is a view of the measurement scale that is very bright, creating a high contrast to see clearly where the boundary intersects the memory lines of the scale. The scale numbers are also large and easy to read. Imitation instruments produced in China cannot compare to the durability, quality or accuracy of ATAGO instruments. Maintaining high standards of quality and attention to detail is the difference which is as clear as the scale of the MASTER units.

3. Contamination Free

The MASTER Series was also designed with a smooth and easy-to-clean grip, eliminating the possibility of food and other samples being trapped which can result in contamination and bacterial growth. The steel and carbon-fiber design is both functional and stylish.

4. Automatic Temperature Compensation

The Automatic Temperature Compensation (ATC) system was also reviewed and improved. This new system allows the MASTER series to have improved accuracy that out performs similar units. While developing the MASTER series, there were many discussions, data gathering of countless tests, and repeated setbacks that our development team had to - and did - overcome. Through this process, ATAGO has applied for a patent on the design of the improved ATC system. Ultimately, the MASTER series reads more accurately than any comparable unit in the market.

5. Endurance

The MASTER Series has passed all water resistance, dust resistance, and drop tests. Instruments were subjected to water jets from four directions, dropped from a height of one meter onto an oak platform, and withstood the pressure changes of air travel. The only replacement part for the MASTER series is the daylight plate and the instruments do not utilize consumable parts or materials, thus keeping the cost for replacement parts to a minimum.

6. Automatic Sample Distribution (ASD)

People who frequently use refractometers have noticed that the daylight plate can get in the way when placing a sample on the prism. To address this problem, ATAGO has developed a spoon-shaped tip, which makes applying the sample easy, and helps to spread the sample across the prism on its own. This makes the instrument even more user-friendly. (Patent Granted)

7. Repair and Service

ATAGO has established a close network of customers by providing excellent customer service support. When an ATAGO instrument needs servicing, not only is each customer treated with respect, but they are also provided with detailed methods and user-specific suggestions on sampling and taking measurements, based on individual needs. ATAGO has refined our user-friendly approach not only to improve our instruments, but to also support our valued customers. ATAGO has many excellent Authorized Service Centers worldwide.

8. Reputation for Quality

ATAGO has built a firm reputation for reliability and quality during its 76-year history. We are a strong company that exports to over 154 countries with continued growth expectations. We have received ISO certification, and our integrated system for producing and marketing our products, based on the "Plan-Do-Check-Act" cycle, is essential in promoting the ATAGO name.
ATAGO products have been awarded “AAA”, the highest rank offered by Standard & Poor's Japan SME Grading for 2 consecutive years.

We at ATAGO are confident that the MASTER series will surpass your expectations.