1. Introduction
The GOYOJO GT128 Digital Refractometer is an optical instrument designed for precise measurement of sugar content in various water samples, foods, fruits, and crops. Utilizing advanced optical principles, it provides accurate and rapid analysis. This device is widely applicable in the food industry, beverage industry, agriculture, and agricultural food processing sectors.
Key features include ease of operation, compact size, lightweight design, and portability, making it ideal for both laboratory and field use.
Figure 1: GOYOJO GT128 Digital Refractometer
2. Product Features
- No moving parts, ensuring high sensitivity and a wide dynamic linear range.
- Requires minimal sample and reagent usage, facilitating fast analysis.
- Battery-powered with low power consumption, featuring an automatic shutdown function after 2 minutes of inactivity to conserve battery life.
- Equipped with an automatic temperature compensation function for enhanced accuracy.
- Operation mode is switchable between refractive index and sugar content (Brix).
- Large display for easy reading of temperature, sugar concentration, and refractive index.
- High precision sensors for accurate and fast measurements (results in less than 3 seconds).
3. Packing List
Please check the contents of your package against the list below:
Figure 2: Packing List
| Item No. | Description | Quantity |
|---|---|---|
| 1 | Digital Refractometer | 1 unit |
| 2 | AAA Alkaline Battery (No.7) | 2 Sections |
| 3 | Instruction manual | 1 book |
| 4 | Certificate of Conformity | 1 copy |
| 5 | Glasses cloth | 2 Blocks |
| 6 | Waterproof rubber mat | 1 piece |
| 7 | Phillips screwdriver | 1 Handle |
| 8 | Dropper | 2 pieces |
| 9 | Cross recessed pan head tapping screws M1.9*5 | 4 Sticks |
4. Setup
4.1 Battery Installation
The device requires 2 AAA alkaline batteries. Locate the battery compartment, insert the batteries according to the polarity markings, and secure the cover.
4.2 Initial Calibration (Zeroing)
Before first use and periodically to ensure accuracy, the refractometer must be calibrated using distilled water.
- Ensure the prism surface (Shengping Platform) is clean and dry.
- Drop 3-5 drops of pure distilled water onto the prism round hole.
- Close the hood.
- Press the "CAL" button. The display will show "DONE" indicating successful calibration.
Figure 3: One-touch Zeroing Calibration
5. Operating Instructions
5.1 Device Overview
Figure 4: Key Description and Operation Explanation
- ON/OFF Button: Powers the device on or off.
- CAL Button: Used for zero calibration with distilled water.
- MEAS Button: Initiates a measurement. Long press to switch between measurement modes (Brix/Refractive Index).
- TEMP Button: Displays the current temperature.
- Monitor: Digital display for readings and status.
- Shengping Platform (Prism): Where the sample is placed.
- Hood: Covers the sample during measurement.
5.2 Measurement Steps
- Ensure the prism surface is clean and dry.
- Add 3 to 5 drops of the solution to be tested onto the prism round hole using the provided dropper.
- Close the hood to prevent light interference and evaporation.
- Press the "MEAS" button. The result will be displayed on the monitor in less than 3 seconds.
Figure 5: Clear and Easy to Follow Measurement Steps
5.3 Mode Switching and Display
The device can display results in Brix percentage or Refractive Index. Long press the "MEAS" button to toggle between these modes.
Figure 6: Dual Mode Display (Brix and Refractive Index)
The device also features automatic temperature compensation, reducing measurement errors caused by temperature differences within its operating range of 10-40°C.
Figure 7: Automatic Temperature Compensation
6. Maintenance and Precautions
- Cleaning: Before each measurement and calibration, ensure the prism's surface at the bottom of the water reservoir platform is clean. Use the provided glasses cloth or a soft, lint-free cloth.
- Storage: Store the instrument in a dry, room-temperature environment. Avoid prolonged exposure to high temperatures and direct sunlight, as this can lead to errors and LCD failure.
- Water Exposure: Do not clean the instrument directly under running water. This can cause water to enter and damage internal components. Wipe clean only.
- Handling: Handle the instrument with care to avoid scratching or impacting the prism surface, which can affect measurement accuracy.
- Evaporation: To maintain measurement accuracy, complete sampling and operation within a short period to minimize the impact of sample evaporation.
- Battery: Low battery power can result in inaccurate measurement data. Replace the AAA batteries promptly when the low battery indicator appears.
7. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Inaccurate readings | Unclean prism surface; improper calibration; low battery; sample evaporation. | Clean the prism thoroughly. Re-calibrate with distilled water. Replace batteries. Perform measurements quickly. |
| Device does not power on | Dead or incorrectly installed batteries. | Check battery polarity. Replace with fresh AAA batteries. |
| "DONE" not displayed after calibration | Insufficient distilled water; prism not clean; CAL button not pressed correctly. | Ensure 3-5 drops of distilled water are used. Clean prism. Press CAL button firmly. |
| LCD display issues (flickering, blank) | Low battery; exposure to extreme temperatures. | Replace batteries. Move device to room temperature and allow it to stabilize. |
8. Specifications
Figure 8: Product Specifications
| Parameter | Value |
|---|---|
| Measurement Range | 0.0 - 55.0% Brix |
| Division Value | 0.5 Brix / 0.1 °C |
| Accuracy | ±0.5 Brix / 1 °C |
| Temperature Compensation | 10 - 80 °C |
| Operating Environment | 10 - 40 °C |
| Sample Volume | ≥0.2 ml (3-5 drops) |
| Testing Time | ≈ 3 seconds |
| Power Supply | 2 AAA alkaline batteries |
| Battery Life | ≈ 2000 tests |
| Model Number | GT128 |
| Brand Name | GOYOJO |
| Certification | CE |
Fruit Sugar Reference Table
The following data is for reference only. The Brix value of fruits may vary depending on the ripeness of the fruit, the variety, and the growing environment.
Figure 9: Fruit Sugar Reference Table
Special Notes:
- The data in the reference table is for reference only; the actual value is subject to measurement.
- Remember the difference between sugar content and refractive index; the two units can be converted, but the value difference is large.
9. User Tips
- Always use fresh, representative samples for the most accurate readings.
- For best results, ensure the sample and the refractometer are at a stable room temperature before measurement.
- When measuring highly viscous liquids, allow a few extra seconds for the sample to spread evenly on the prism.
- Regularly check the battery level, especially before critical measurements, to avoid errors due to low power.
10. Warranty and Support
For any questions, technical support, or warranty inquiries regarding your GOYOJO GT128 Digital Refractometer, please contact the seller or manufacturer directly. Keep your purchase receipt as proof of purchase.
