Handheld refractometers are portable instruments used to measure the refractive index or concentration (e.g., Brix, Salinity) of liquid samples. Key specifications include a Brix range of 0–90%, accuracy of $\pm$0.2% to $\pm$0.5%, Automatic Temperature Compensation (ATC) typically between 10–40°C, and small sample requirements (2-3 drops). They are essential for field testing in food, beverage, and industrial applications. 

Typical Handheld Refractometer Specifications

• Measurement Range: Common models cover 0–32% Brix, 0–53% Brix, or up to 0–90% Brix for high-concentration substances (e.g., honey, syrup).
• Accuracy: Generally $\pm$0.1% to $\pm$0.2% for Brix, with high-precision models reaching $\pm$0.1%.
• Temperature Compensation (ATC): Most modern units feature ATC, allowing accurate readings without manual temperature correction, usually within a 10°C to 40°C range.
• Sample Volume: Requires a very small amount, typically 0.1 ml to 2-3 drops.
• Resolution: Often 0.1% Brix or 0.1°C.
• Weight & Dimensions: Lightweight and portable, often around 100g to 300g, designed for handheld use.
• Materials: Durable construction with metal or ABS plastic bodies, often with IP65 or higher, indicating they are water-resistant and easy to clean.