G-WON GMK-702AC Handheld Digital Refractometer for Food and Fruit Brix Measurement
| Brand | G-WON |
|---|---|
| Origin | South Korea |
| Model | GMK-702AC |
| Product Type | Handheld Refractometer |
| Temperature Compensation | Yes (ATC) |
| Display | Digital LCD |
| Measurement Range | 45–90 % Brix |
| Accuracy | ±0.2 % Brix |
| Certifications | CE, EMC |
Overview
The G-WON GMK-702AC is a precision-engineered handheld digital refractometer designed specifically for rapid, field-deployable Brix concentration measurement in food-grade liquid samples—particularly fruit juices, syrups, jams, honey, and other high-sugar agricultural products. It operates on the principle of critical-angle refractometry: light passing through a sample undergoes refraction at the prism–sample interface; the resulting critical angle correlates directly with the solution’s refractive index, which is empirically calibrated to % Brix via standardized sucrose-water reference solutions per ISO 2173 and AOAC Official Method 932.12. The instrument incorporates built-in Automatic Temperature Compensation (ATC) across 10–40 °C, eliminating manual correction and ensuring metrological consistency without external thermostatic control. Its optical path utilizes high-transmittance BK7 glass prisms with anti-scratch coating, optimized for stability under repeated field handling and variable ambient conditions.
Key Features
- Digital LCD display with backlight for high-contrast readability in low-light environments (e.g., orchard packing lines or cold storage rooms)
- Integrated ATC system using embedded thermistor sensors—compensates refractive index shifts in real time without user intervention
- One-touch auto-calibration function using distilled water or factory-set reference standard; prevents erroneous readings if calibration fails (instrument blocks measurement until successful calibration is confirmed)
- Low-battery indicator with audible alert and on-screen icon—ensures uninterrupted operation during extended QC shifts
- Ergonomic, IP65-rated housing with rubberized grip and sealed optical chamber—resistant to moisture, dust, and incidental splashes encountered in food processing environments
- Compliant with electromagnetic compatibility (EMC) Directive 2014/30/EU and CE marking requirements for safe operation in EU-regulated facilities
Sample Compatibility & Compliance
The GMK-702AC is validated for use with clear to mildly turbid aqueous sugar solutions where suspended solids do not exceed 5 wt% and particle size remains below 50 µm—conditions typical of clarified fruit extracts, nectars, and post-filtration syrups. It is not intended for viscous, opaque, or highly particulate matrices (e.g., pulpy mango puree or unfiltered molasses) without prior centrifugation or filtration. All calibration and verification procedures align with Good Laboratory Practice (GLP) documentation standards. While the device itself does not generate audit trails, its calibration status, measurement timestamp (via optional PC interface), and operator ID input support traceability frameworks required under FDA 21 CFR Part 11 when integrated into validated quality management systems.
Software & Data Management
The GMK-702AC operates as a standalone instrument with no embedded memory or Bluetooth/Wi-Fi connectivity. However, it supports optional RS-232 serial output (via proprietary cable adapter) for direct data streaming to Windows-based laboratory information management systems (LIMS) or Excel-compatible logging software. Exported records include Brix value, temperature reading, date/time stamp, and calibration flag status. Firmware updates are performed offline using G-WON’s certified configuration utility—ensuring version control and integrity verification prior to deployment in regulated settings.
Applications
- Harvest readiness assessment in orchards and vineyards—quantifying ripeness via juice Brix prior to picking
- In-line quality screening at juice extraction and concentration facilities to maintain batch consistency
- Supplier verification of incoming raw materials (e.g., concentrated apple juice, cane syrup) against contractual Brix specifications
- Routine QC testing in confectionery R&D labs for formulation development and shelf-life studies
- Teaching laboratories demonstrating colligative property relationships between solute concentration and refractive index
FAQ
Does the GMK-702AC require daily calibration?
Yes—calibration with distilled water or certified Brix standard is mandatory before each measurement session. The instrument enforces this protocol by disabling measurement mode until successful calibration is confirmed.
Can it measure samples below 45 % Brix?
No—the optical design and internal calibration curve are optimized exclusively for the 45–90 % Brix range. For lower-concentration applications (e.g., soft drinks or wine must), a complementary model such as the GMK-301 series is recommended.
Is temperature compensation linear across the full operating range?
ATC employs a multi-point polynomial algorithm derived from empirical refractive index vs. temperature curves for sucrose solutions, providing non-linear compensation compliant with ISO 2173 Annex C.
What maintenance is required for long-term accuracy?
Prism surfaces must be cleaned after each use with lens tissue and reagent-grade isopropanol; avoid abrasive cloths or acetone. Annual verification against NIST-traceable Brix standards is advised for GLP-compliant operations.
