VEE GEE BX-1 Operation Manual Download Page 2

Refractometer

 

Components

Calibration Ring

Mechanism used to zero or calibrate the refractometer, 

without the requirement of additional tools.

Rubber Hood

Houses and protects the focusable lens.  Prevents 

light from entering through the eyepiece during use.

Rubber Grip

Insulates the refractometer 

against hand heat for accurate 

results.

Non-Roll Stand

Protects against damage to the 

instrument when set down between 

measurements.

Daylight Plate & Prism

The prism and sample are covered by 

the daylight plate during readings. 

This refractometer is an optical instrument -- it can become damaged if dropped or handled in a rough manner.

The prism is made of optical glass and is susceptible to scratches -- do not apply any rough or abrasive 

material and take care when cleaning the prism.

After each use, clean the prism surface and daylight plate with a soft cloth or tissue soaked in water and 

wipe off with a dry cloth or tissue.

Do not hold the refractometer under a stream of water from a faucet.  Do not splash it with or dip it in water.

If the surface of the prism becomes coated with an oily solution or similar, it will repel test samples and 
affect readings.  If this occurs, the prism should be cleaned with a weakened detergent or similar solvent.

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Calibration

Precautions

Calibration should be conducted at the start of each day or when any 

shifts in ambient temperature occur. If recalibration is impractical, refer 

to the directions and temperature correction table on the following page.  

For standard calibration procedures, please follow the directions below.

Open the daylight plate and apply one or two drops of distilled water on to 

the surface of the prism. Hold the prism at an angle close to parallel with 

the floor so the distilled water will not run off of the prism.

Gently close the daylight plate over the prism. The distilled water should 

spread as a thin, even layer in between the daylight plate and the prism.  

By looking through the daylight plate, ensure that the distilled water covers 

the ENTIRE surface of the prism. If there are bubbles and gaps or if the 

distilled water is only on one portion of the prism, the distilled water must 

be reapplied (Figure 1). Inaccurate calibrations will result if the prism is 

not covered correctly.

Looking through the eyepiece, hold the refractometer and direct the daylight 

plate upwards towards light. If the scale is not in focus, adjust it by gently 

turning the eyepiece (rubber hood) either clockwise or counterclockwise.  

Be careful not to overturn the focusing mechanism.

When the refractometer scale is viewed through the eyepiece, the upper 

field of view will be seen as blue and the lower field will be seen as white 

(Figure 2). Confirm that the boundary line crosses the scale at “0” (Figure 3).

If the boundary line falls above or below zero, gently loosen the screw on the 

calibration ring. While looking through the eyepiece, gently turn the calibration 

ring clockwise or counterclockwise until the boundary line is at zero.  Once 

this is achieved gently tighten down the set screw. (NOTE: Do not over-tight-

en.  If the set screw is over-tightened, the boundary line may shift slightly).

When calibration is complete, gently wipe the prism using tissue paper.

Thank you for purchasing this VEE GEE Refractometer.  With the user in mind, VEE GEE Refractometers are built 

from modern designs and, with proper care, this instrument should provide many years of reliable performance.  

It’s recommended this manual is read entirely before using the refractometer for the first time.

Introduction

Figure 1

Figure 2

Figure 3

Figure 4

Figure 3

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General

 

Use

Open the daylight plate and apply one or two drops of the sample solution 

to the surface of the prism.  Hold the prism at an angle close to parallel 

with the floor so the sample will not run off of the prism.

Gently close the daylight plate over the prism.  The sample solution should 

spread as a thin, even layer in between the daylight plate and the prism.  

By looking through the daylight plate, ensure that the sample solution 

covers the ENTIRE surface of the prism.  If there are bubbles and gaps or if 

the sample is only on one portion of the prism, the sample solution must 

be reapplied (Figure 1).  Inaccurate readings will result if the prism is not 

covered correctly.

Looking through the eyepiece, hold the refractometer and direct the daylight 

plate upwards towards light.  If the scale is not in focus, adjust it by gently 

turning the eyepiece (rubber hood) either clockwise or counterclockwise.  

Be careful not to overturn the focusing mechanism.

When the refractometer scale is viewed through the eyepiece, the upper 

field of view will be seen as blue and the lower field will be seen as white 

(Figure 4).  The reading is taken at the point where the boundary line of the 

blue and white fields crosses the scale (Figure 5).  The value is the Brix% 

reading of the sample.

When each measurement is complete, the sample must be cleaned from 

the prism using tissue paper and water.

Calibration Ring Set Screw

Secures the calibration ring in place to 

protect from any shifts which could occur 

during use.

Figure 5

Figure 3

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