User's Guide
Brix Refractometer
Models RF18
Introduction
Congratulations on your purchase of the Extech RF18 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 18% Brix
Resolution 0.1%
Dimensions 1.2 x 1.6 x 6.7" (30 x 40 x 170mm);
Weight 3.2 oz. (91g)
Description
1. Prism 3 2
1
5
4
5. Eyepiece
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
Bad Bad Good 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
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 RF18 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%.
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All rights reserved including the right of reproduction in whole or in part in any form.
Temperature Compensation Table (Referenced To 20
O
C) o
% 5 10 15 20 25 30 35 40 45 50 55 60 65 70
C Subtract the following from the measurement
10 0.58 0.59 0.61 0.64 0.67 0.69 0.71 0.72 0.74 0.74 0.74 0.75 0.76 0.77
11 0.51 0.54 0.55 0.58 0.61 0.63 0.65 0.65 0.67 0.67 0.67 0.68 0.68 0.69
12 0.47 0.49 0.50 0.52 0.55 0.57 0.58 0.58 0.60 0.60 0.60 0.60 0.61 0.61
13 0.42 0.44 0.44 0.45 0.49 0.50 0.51 0.51 0.53 0.53 0.53 0.53 0.53 0.53
14 0.37 0.38 0.39 0.40 0.42 0.43 0.44 0.44 0.45 0.45 0.45 0.45 0.45 0.46
15 0.31 0.32 0.33 0.34 0.35 0.36 0.37 0.37 0.38 0.38 0.38 0.38 0.38 0.38
16 0.25 0.26 0.27 0.28 0.28 0.29 0.30 0.30 0.30 0.31 0.31 0.31 0.31 0.31
17 0.19 0.20 '0.20 0.21 0.21 0.22 0.22 0.23 0.23 0.23 0.23 0.23 0.23 0.23
18 0.13 0.13 0.14 0.14 0.14 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15 0.15
19 0.06 0.07 0.07 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08
Add the following to the measurement
21 0.07 0.07 0.07 0.07 0.07 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08
22 0.14 0.14 0.14 0.14 0.15 0.15 0.16 0.16 0.16 0.16 0.16 0.16 0.16 0.15
23 0.21 0.21 0.22 0.22 0.23 0.23 0.23 0.23 0.24 0.24 0.24 0.24 0.23 0.22
24 0.28 0.29 0.29 0.30 0.30 0.31 0.31 0.31 0.31 0.31 0.32 0.32 0.31 0.31
25 0.35 0.36 0.37 0.38 0.38 0.39 0.39 0.40 0.40 0.40 0.40 0.40 0.39 0.39
26 0.43 0.44 0.44 0.46 0.46 0.47 0.47 0.48 0.48 0.48 0.48 0.48 0.47 0.47
27 0.51 0.52 0.53 0.54 0.55 0.55 0.56 0.56 0.56 0.56 0.56 0.56 0.55 0.55
28 0.59 0.60 0.61 0.62 0.63 0.64 0.64 0.65 0.65 0.64 0.64 0.64 0.64 0.63
29 0.67 0.68 0.69 0.70 0.71 0.72 0.73 0.73 0.73 0.73 0.73 0.72 0.72 0.71
30 0.75 0.77 0.78 0.79 '0.80 '0.81 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
Warranty
EXTECH INSTRUMENTS CORPORATION warrants this instrument to be free of defects in parts and workmanship for one year from date of shipment (a six month limited warranty applies on sensors and cables). If it should become necessary to return the instrument for service during or beyond the warranty period, contact the Customer Service Department at (781) 890-7440 ext. 210 for authorization or visit our website at www.extech.com (click on ‘Contact Extech’ and go to ‘Service
Department’ to request an RA number). A Return Authorization (RA) number must be issued before any product is returned to Extech. The sender is responsible for shipping charges, freight, insurance and proper packaging to prevent damage in transit. This warranty does not apply to defects resulting from action of the user such as misuse, improper wiring, operation outside of specification, improper maintenance or repair, or unauthorized modification. Extech specifically disclaims any implied warranties or merchantability or fitness for a specific purpose and will not be liable for any direct, indirect, incidental or consequential damages. Extech's total liability is limited to repair or replacement of the product. The warranty set forth above is inclusive and no other warranty, whether written or oral, is expressed or implied. www.extech.com
RF18 V1.1 3/05
