Hiệu chuẩn máy đo độ ngọt, mặn REFRACTOMETER

Hiệu chuẩn máy đo độ ngọt, mặn

Hiệu chuẩn máy đo độ ngọt, mặn




  1. Scope

This calibration procedure is commonly used for meters of salinity, sweetness based on the principle of refraction.

  1. Requested equipments
  • Standard salinity solution (5%NaCl, 10% NaCl, 15%NaCl…), standard sweetness solution (15%Brix, 40% Brix, 60% Brix, …)
  • Wash bottle containing distilled water
  • Digital temperature meter
  • Soft towel
  1. Calibration
  • Ensure that the temperature of solution as well as meter is at 20oC or 25o The manufacturer shall provide the ideal temperature for the measurement, typically at 20oC. If the current temperature is different than the temperature given by the manufacturer, the temperature compensation table may be used to have more accurate results:


  • Select the available standard solutions which are consistent with type of solution, the measuring range of the equipment.
  • Wash the surface of the refractometer before it is measured with distilled water. Then pour from 2-3 drops of standard solutions (standard salinity solution, or standard sweetness solution) on its surface. Cover the plastic lid, and wait for about 1 minute until the sample is stable

2 3

  • Look into the lens of the refractometer to see the measurement result. Draw the limit line between 2 zones: light zone and dark zone in the lens which indicate the measurement result.



Note: after covering, the surface of measuring glass should not have the bubble or any dry areas (see the below figure) to avoid the influence on the measurement result.


  • Then, open the lid of the measuring surface, use a soft cloth to wipe, use wash bottle to spay the distilled water on the surface of measuring surface, wipe again and then proceed the next measurement.
  1. Error

Error given by the customer will be applied for all measurement, unless otherwise provisions. If the customer does not offer any rule, the specification of manufacturer or other source of reference will be used. If not, the error of the equipment will be +/- 1 graduation or +/- 1% of the entire measurement range.

  1. Adjustment

If the error of measurement result is too larger than the permitted error, we conduct the adjustment by turning the screw located on the surface of lens:


  1. Other meters

With the digital refractometer (its form is like the below figure), we also conduct the measurement as mentioned above, but remember to press “Zero” before measuring. Press “Read” for each measurement. The reference temperature is available and selective between 20oC or 25oC.


For digital refractometer, where the error exceeds the permitted error, the adjustment will be based on the guide of manufacturer. Each manufacturer will have its own adjustment procedures for each equipment.


This procedure can be referred:

  • Refractometer for Sucrose Measurements, Model MA781, Maker: Milwaukee
  • Brix Refractometers User’s Guide, Model RF10 and RF15, Maker: Extech

Web: Caltek.com.vn

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