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User's Guide

Brix Refractometers

Models RF10 and RF15 (with ATC)

Introduction

Congratulations on your purchase of the Extech RF10 or RF15 Brix

Refractometer. Precision optical instruments should be handled gently;

avoid touching the optical surface. Careful use of these instruments will

provide years of reliable service.

Specifications

Range 0 to 32% Brix

Resolution 0.2%

Dimensions RF10: 168 x 32 x 32mm

RF15: 159 x 35 x 35mm

Weight RF10: 91g; RF15: 200g

Description

1. Eyepiece

2. Mirror Tube

3. Adjustment screw

4. Cover Plate

5. Prism

Operation

This instrument measures the refractive index of a sample. The measurement

is displayed in % Brix.

1. Zero Adjustment

Cover the prism with distilled water (several drops will suffice). Close the

cover plate and rotate the adjustment screw until the light/dark boundary

(shadowline) lines up with the zero line. After the zero adjustment, clean

the prism with a soft cloth.

2. Sample Preparation and Reading

To take a sample reading, simply place a few drops of a sample liquid on

the measurement prism at the end of the instrument. Close the prism

cover plate so that the liquid spreads across the entire surface of the prism

without air bubbles or dry spots (see

diagram). Allow the sample to remain

on the prism for approximately 30

seconds.

While holding the instrument under a

light source, look through the

eyepiece. The sucrose concentration

is determined by the intersection of

the boundary of the light and dark

fields (known as the shadowline) on

the printed scale. If the scale appears out of focus, the eyepiece may be

adjusted by rotating the knurled portion of the eyepiece. The instrument

also features an eye-guard to prevent stray light from entering the

eyepiece and causing reflections.

It may be necessary to adjust the position of the light source to maximize

the contrast of the shadowline. Under normal conditions, optimal contrast

is obtained by holding the instrument underneath and perpendicular to a

light source.

Once a reading has been taken, wipe dry with a clean cloth (do not wash

or rinse) and place the instrument in the supplied plastic case. Store the

instrument in a safe, dry environment.

Note: The Distilled water temperature, used for zero adjustment, and the

sample liquid temperature should be the same. If the temperature of the

samples fluctuates, zero the refractometer every 30 minutes (RF10 only).

3. Temperature Compensation (RF15 has Auto Temp. Comp.)

Temperature is one of the single most important factors influencing

accurate refractometer readings and is one of the largest sources of

measurement error. Temperature compensation relieves the user of the

responsibility to measure temperature and apply a correction factor when

taking readings. The RF15 makes this correction automatically. When

ambient temperature strays from 68°F (20°C), readings are automatically

adjusted to compensate for temperature variance between 50°F to 86°F

(10°C to 30°C).

The RF10 Refractometer has been designed for use with a 20°C standard

temperature. Therefore, if the temperature of the measurement deviates

from 20°C, the reading must be manually compensated in accordance

with the Temperature Compensation Table below.

Example: A reading of 20% at 28°C is compensated thusly: 20% +

0.62%=20.62%.

Temperature Compensation Table (Referenced To 20

5 10 15 20 25 30 35 40 45 50 55 60 65 70

Subtract the following from the measurement

0.58

0.59

0.61

0.64

0.67

0.69

0.71

0.72

0.74

0.74 0.75 0.76 0.77

0.51

0.54

0.55

0.58

0.61

0.63

0.65

0.67

0.67 0.68 0.68 0.69

0.47

0.49

0.50

0.52

0.55

0.57

0.58

0.60

0.60 0.60 0.61 0.61

0.42

0.44

0.45

0.49

0.50

0.51

0.53

0.53 0.53 0.53 0.53

0.37

0.38

0.39

0.40

0.42

0.43

0.44

0.45

0.45 0.45 0.45 0.46

0.31

0.32

0.33

0.34

0.35

0.36

0.37

0.38

0.38 0.38 0.38 0.38

0.25

0.26

0.27

0.28

0.29

0.30

0.31

0.31 0.31 0.31 0.31

0.19

0.20

'0.20

0.21

0.22

0.23

0.23 0.23 0.23 0.23

0.13

0.14

0.15

0.15 0.15 0.15 0.15

0.06

0.07

0.08

0.08 0.08 0.08 0.08

Add the following to the measurement

0.07

0.08

0.08 0.08 0.08 0.08

0.14

0.15

0.16

0.16 0.16 0.16 0.15

0.21

0.22

0.23

0.24

0.24 0.24 0.23 0.22

0.28

0.29

0.30

0.31

0.32 0.32 0.31 0.31

0.35

0.36

0.37

0.38

0.39

0.40

0.40 0.40 0.39 0.39

0.43

0.44

0.46

0.47

0.48

0.48 0.48 0.47 0.47

0.51

0.52

0.53

0.54

0.55

0.56

0.56 0.56 0.55 0.55

0.59

0.60

0.61

0.62

0.63

0.64

0.65

0.64

0.64 0.64 0.64 0.63

0.67

0.68

0.69

0.70

0.71

0.72

0.73

0.73 0.72 0.72 0.71

0.75

0.77

0.78

0.79

'0.80

'0.81

0.81

0.82

0.81

0.81 0.81 0.80 0.79

Source: International Commission for Uniform Methods of Sugar Analysis (1966)

International Brix% Scale

Brix to Refractive Index (nD) Conversion Table

% nD % nD % nD % nD % nD % nD

0 1.333 15 1.3557

30 1.3811

45 1.4097

60 1.4419 75 1.4778

1 1.3344

16 1.3573

31 1.3829

46 1.4118

61 1.4442 76 1.4804

2 1.3359

17 1.3589

32 1.3847

47 1.4138

62 1.4464 77 1.4829

3 1.3373

18 1.3605

33 1.3866

48 1.4159

63 1.4488 78 1.4855

4 1.3388

19 1.3622

34 1.3884

49 1.418 64 1.4511 79 1.4881

5 1.3403

20 1.3638

35 1.3903

50 1.42 65 1.4534 80 1.4907

6 1.3418

21 1.3655

36 1.3922

51 1.4222

66 1.4558 81 1.4933

7 1.3433

22 1.3672

37 1.3941

52 1.4243

67 1.4582 82 1.496

8 1.3448

23 1.3689

38 1.396 53 1.4264

68 1.4606 83 1.4987

9 1.3463

24 1.3706

39 1.3979

54 1.4286

69 1.463 84 1.5014

10 1.3478

25 1.3723

40 1.3998

55 1.4308

70 1.4654 85 1.5041

11 1.3494

26 1.374 41 1.4018

56 1.4329

71 1.4678 86 1.5068

12 1.3509

27 1.3758

42 1.4037

57 1.4352

72 1.4703 87 1.5096

13 1.3525

28 1.3776

43 1.4057

58 1.4374

73 1.4728 88 1.5123

14 1.3541

29 1.3793

44 1.4077

59 1.4396

74 1.4753 89 1.5151

Source: International Sugar Analysis Committee

V3.0 7/08

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