KERN Analogue Refractometer

1. Technical Data

Example scales are provided for ORA 3AA/AB and ORA 4AA/AB.

2. Description

The refractometer consists of the following main parts:

• 1. Prism cover: Protects the prism.
• 2. Prism surface: The measuring surface where the sample is placed.
• 3. Adjustment screw: Used for zero point calibration.
• 4. Eyepiece with rubber eyeshade: For viewing the scale and boundary line.
• 5. Diopter adjustment ring: Adjusts focus for the user's eyesight.
• 6. Optical tubes with rubber grip: Housing for optical components.

3. General Information

3.1 Intended Use

The refractometer is a measuring instrument for determining the refractive index of transparent substances in liquid or solid states. It works by observing the behavior of light passing from a prism with known properties to the substance being tested. Using the refractometer for purposes other than its intended use may be hazardous. The manufacturer is not liable for damages caused by improper use.

3.2 Warranty

The warranty is void in the event of:

• Failure to observe the instructions in the operating manual.
• Use for purposes other than those described.
• Modifications or opening the device housing.
• Mechanical damage or damage resulting from media, liquids, or natural wear and tear.

4. Basic Safety Information

4.1 Follow the Instructions in the Operating Manual

Carefully read through this operating manual, even if you have prior experience with KERN refractometers. Note that each language version includes a non-authoritative translation; the original German document is the definitive version.

4.2 Warning

• Avoid contact of acids with skin or eyes. If acid contacts skin, flush with copious amounts of water. Shower if larger areas are affected.
• If acid contacts eyes, keep eyelids open and flush with running lukewarm water from the outer corner to the inner corner for at least 15 minutes. Consult a doctor or ophthalmologist immediately.
• Thoroughly clean the refractometer after each use.
• Do not expose the refractometer to extreme temperatures, high mechanical stresses, strong direct sunlight, or high humidity.
• This refractometer is not a toy. Keep out of reach of children.
• Ensure you will not be hit by other objects while using the refractometer, as this could cause serious eye injuries.
• The rubber eyeshade may cause skin irritation with prolonged contact. Consult a doctor if this occurs.
• Do not touch the lenses with your fingers.

5. Supplied Items

After unpacking, check that all listed parts are supplied before first use. Replace damaged or faulty parts immediately and do not put them into operation.

• Refractometer
• Storage box
• Pipette
• Adjustment tool
• Cleaning cloth
• Calibration liquid (Distilled water)

6. Before the First Use

Remove any protective film from the prism surface [2] and check that the rubber eye-cup [4] is fitted correctly.

7. Use/Measurement

The refractometer allows quick and accurate determination of the refractive index of transparent substances (liquid or solid). For correct measurement, the device should be adjusted before use. Ensure hands are dry when handling the device.

7.1 Zero Point Calibration

1. Hold the refractometer against a bright light source and look through the eyepiece [5], holding the rubber eyeshade [4] close to your eye/glasses.
2. Rotate the eyepiece [5] to adjust for your eyesight until the scale is sharp.
3. Open the prism cover [1].
4. Thoroughly clean the prism [2] and the underside of the prism cover [1] with a soft cloth or soft paper (use alcohol if necessary) and wipe dry.
5. Apply a few drops of the calibration liquid [10] onto the prism surface [2].
6. Close the prism cover [1]. Ensure the fluid moistens most of the prism surface without air bubbles between the measuring prism [2] and prism cover [1].
7. Wait approximately 30 seconds for the fluid and prism temperatures to equalize.
8. Look through the eyepiece [4] while pointing the refractometer's prism surface [2] at a bright light source.
9. You will see a bright and a blue field. The boundary line between them indicates the measured value on the scale, visible through the eyepiece [4].
10. Use the supplied adjustment tool [11] to turn the adjustment screw [3] (under the rubber cap) behind the prism surface [2]. Adjust the scale by moving the boundary line up or down until the device is optimally set.
11. Calibration values: ORA 3AA/3AB: 0% Brix / 1.000 SG wort; ORA 4AA/4AB: 0° Plato.
12. Repeat step 4 (cleaning).

Important! The ambient/room temperature and sample temperature influence the measurement result. Models with "AB" in their name are designed for an ambient temperature of +20°C. If measurements are taken at other temperatures, results must be corrected using the table in Annex, Point 14. Models with "AA" are equipped with automatic temperature compensation (ATC) for temperatures between +10°C and +30°C.

7.2 Additional Advice

Ensure samples are representative. For easily evaporating samples, measurements should be quick. Samples should be at the same temperature as the instrument for accurate results.

7.3 Measuring Procedure

1. Ensure your hands are dry.
2. Open the prism cover [1]. Use the supplied pipette [8] to apply a few drops of the sample liquid onto the prism surface [2].
3. Close the prism cover [1]. Spread the liquid evenly by pressing down on the cover and eliminate any air bubbles.
4. Hold the device horizontally and wait about 30 seconds for temperature equalization.
5. View the measurement scale through the eyepiece [4]. Point the prism surface [2] at a bright light source.
6. Rotate the adjustment ring [5] on the eyepiece [4] to adjust focus.
7. The boundary line on the scale indicates the concentration. This bright/dark boundary shows the result.
8. If using a refractometer without ATC and the temperature deviates from +20°C, correct the measured result using the temperature correction table [13].
9. Carefully clean the pipette [8] and refractometer after measurement.

Important! After every measurement, use a lint-free, absorbent cloth to remove fluids from the prism surface [2] and prism cover [1]. Then carefully clean the prism and cover with a cloth moistened with water or alcohol (if necessary), and dry both parts with a soft, dry, lint-free cloth. Avoid rubbing the prism [2].

8. Cleaning and Maintenance

Clean the refractometer with a soft, lint-free cloth moistened with water or alcohol. Do not use aggressive or abrasive cleaning agents. Never immerse the device in water or hold it under running water. Never handle the device with wet or damp hands.

Do not touch the measuring prism [2] with hard tools (plastic, wood, rubber, metal, glass, etc.), as these can damage the soft prism glass and cause measurement errors.

The refractometer is maintenance-free. Cleaning should be performed immediately before and after each use to maximize lifespan and optimize measurement results.

9. Storage

Store the refractometer in a dry, non-corrosive environment, preferably between 10°C and 30°C.

10. Service

For questions regarding setup or use, or if unexpected problems occur, contact your dealer. The device housing should only be opened by trained service technicians authorized by KERN.

11. Disposal

Packaging materials are environmentally friendly and can be disposed of via local recycling facilities. The device and storage box should be disposed of by the operator in accordance with applicable national or regional regulations at the place of use.

12. Additional Information

The product may differ slightly from the illustrations. Avoid exposing the refractometer to direct sunlight. Never bring the refractometer into contact with solvents.

13. Brix to Refractive Index (nD) Conversion Table

Data from "ICUMSA" International Commission for Uniform Methods of Sugar Analysis, at 20°C and 589 nm wavelength.

14. Annex

Table 1: International Temperature Correction Table for °Brix (% sugar gradient)

Correct the result by the following values (refractometer must be correctly adjusted at 20°C).