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A drop of fruit juice, half a drop of honey, or even car coolant—within just a few seconds, this palm-sized instrument can reveal their concentration secrets. Among numerous testing instruments, the handheld refractometer holds an important position thanks to its unique advantages. Whether it's testing in laboratories, quality control in industrial production, or small inspections in daily life, it can perform brilliantly. Now, let's delve into the principles, applications, and usage methods of the handheld refractometer.   I. Working Principle: Ingenious Application of Light Refraction Phenomenon   Light travels at different speeds in different transparent media, and when it passes from one medium to another, its direction of propagation changes—this is the phenomenon of light refraction. The handheld refractometer makes clever use of this property.   Solutions with different concentrations have different refractive indices. When light passes through the solution to be tested, the refraction angle changes with the concentration. The handheld refractometer captures these changes in refraction angle through its internal optical system, and then converts the refraction angle into directly readable concentration values (such as sugar content, salinity, alcohol concentration, etc.) based on pre-set corresponding relationships. The blue-white boundary line we see in the eyepiece is exactly the light-dark junction formed by different refracted light rays, and the position of this boundary directly corresponds to the concentration of the solution.    II. Versatile Applications: A Quality Guardian Across Multiple Fields   1. Sugar Content Measurement: The measurement of sugar content (Brix) is the most classic application of handheld refractometers. During the fruit harvest season, farmers can use it to quickly determine the sugar content of fruits such as grapes, apples, and watermelons to judge the optimal picking time. Juice factories rely on it to monitor the concentration in the production line—with just one or two drops of sample, results are available in seconds, preventing sweetness imbalance in entire batches of products. For example, the RHB-32ATC sugar refractometer can measure sugar content in the range of 0-32% with an error of only ±0.2%, making it suitable for most fruit farmers and juice manufacturers.   2. Industrial Production: The RHB series of handheld refractometers can be used to measure the concentration of various industrial solutions, such as cutting fluids and grinding fluids. In industrial production, the stable concentration of cutting fluids and grinding fluids is crucial to ensuring processing quality. The emergence of handheld refractometers not only ensures the stability of the processing process but also avoids raw material waste caused by improper concentration, significantly reducing the comprehensive production cost. It is a practical tool in industrial processing for guaranteeing production efficiency and product quality.   3. Salinity Detection: Precise control of salinity is crucial in the production of pickled foods, seafood processing, and seasoning manufacturing. In the case of pickled vegetables, appropriate salinity ensures their flavor and prevents spoilage. Handheld refractometers can quickly detect the concentration of brine, ensuring the smooth progress of the production process. In mariculture, salinity is related to the survival of fish. Salinity refractometers (such as the RHS-28ATC) can measure salinity in the range of 0-28%, helping farmers adjust the salinity of water bodies.   4. Honey Testing: The core indicator of honey quality—moisture content—is calculated using a refractometer. Professional honey refractometers (such as the RHB-90ATC) can display sugar content, Baume degree, and moisture content simultaneously. When the moisture content of honey exceeds 20%, it is prone to fermentation and deterioration. Therefore, beekeepers need to ensure that the measured value is within the safe range of 20% before capping.   5.Alcohol Concentration Detection: In the brewing industry, alcohol concentration is a crucial parameter for measuring wine quality. From the fermentation process to the testing of finished products, monitoring alcohol concentration is indispensable. Handheld refractometers can quickly measure the alcohol concentration in fermentation broth, helping brewers judge the fermentation progress, adjust fermentation conditions in a timely manner, and ensure the quality of the wine.     For some beverages that require alcohol content control, such as pre-mixed cocktails, handheld refractometers can accurately detect their alcohol concentration, ensuring that the products meet relevant standards and consumer needs.     In industrial fields, alcohol concentration detection is also required in certain production processes that use alcohol as a raw material. For example, in cosmetics production, alcohol is often used as a solvent, and its concentration affects the performance and stability of products. Handheld refractometers can provide rapid concentration detection support for the production process.     6. Battery Fluid and coolant Detection: The concentration of battery fluid has a significant impact on battery performance and service life. Taking lead-acid batteries as an example, measuring the specific gravity of battery fluid (related to concentration) with a handheld refractometer can determine whether the battery's charging and discharging status is normal, detect potential battery problems in time, and ensure the stable operation of the battery in various devices. For instance, the RHA-200ATC can measure the specific gravity of battery fluid in the range of 1.100-1.400; if the measured value is too low, it indicates that the battery needs to be charged or replaced.     Ethylene glycol and propylene glycol are the main components of automotive coolant, and their concentration determines the freezing point. The concentration of propylene glycol or ethylene glycol must be maintained within an appropriate range to effectively exert the cooling effect, prevent equipment overheating, and ensure it operates in the optimal working state.   III. Usage Method: Accurate Measurement in Simple Steps     1. Preparation   First, ensure that the prism surface of the handheld refractometer is clean and free of impurities. You can gently wipe the prism with a soft flannel or special wiping paper to avoid scratches. If it is the first time to use or has not been used for a long time, calibration is required. Calibration method: Drop a few drops of distilled water onto the prism, close the cover, point the instrument at a light source, and adjust the eyepiece to make the scale in the field of view clear. At this point, the light-dark boundary line should align with the 0 scale. If not, use a special screwdriver to adjust the zero adjustment screw until they align. After calibration, wipe off the distilled water drops.     2. Measurement process   Open the cover, use a dropper to take a small amount of the solution to be tested (such as fruit juice, salt water, alcohol solution, battery fluid, etc.), and drop 1-2 drops onto the prism surface. Ensure the solution covers the prism evenly without any bubbles.   Gently close the cover to prevent the solution from spilling or creating new bubbles. Point the light inlet of the instrument at a bright light source (but avoid direct sunlight), put your eye close to the eyepiece for observation, adjust the eyepiece diopter ring to make the scale clear, and read the scale value corresponding to the light-dark boundary line—this value is the concentration of the solution to be tested. If the instrument has a temperature compensation function, the measurement result will be automatically corrected to the concentration value at the standard temperature; if there is no temperature compensation function, the reading needs to be corrected according to the temperature correction table and the ambient temperature during measurement to obtain the accurate concentration.     3. Cleaning and storage   After measurement, immediately use a flannel or wiping paper to gently wipe off the residual solution on the prism surface and the cover, then dry them with a clean, soft cloth. Store the instrument properly in a dry, clean storage box to avoid collision and moisture, so that it can be used next time.