Hanna Digital Refractometers Hanna Digital Refractometers are rugged, portable, water-resistant devices that eliminates the uncertainty associated with mechanical refractometers. • Easy measurement · Place a few drops of the sample in the well and press the READ key • Quick, accurate results · Readings are displayed in approximately 1.5 seconds • Rubberized keypad • IP65 water protection · Built to perform under harsh laboratory and field conditions • Small sample size · Sample size can be as small as 2 metric drops • Dual-level LCD · The dual-level LCD displays measurement and temperature readings simultaneously • ABS thermoplastic casing • Stainless steel sample well · Easy to clean and corrosion-resistant • Startup · When powered on, the meter displays battery life and the set measurement units • Unit selection · Pressing the RANGE key quickly cycles through the units of measurement (if applicable) • Automatic Temperature Compensation · For exceptionally accurate measurements • Single-point calibration · Calibrate with distilled or deionized water • BEPS (Battery Error Prevention System) • Alerts the user in the event that low battery power could adversely affect readings • Automatic shut-off after three minutes of non-use Refractive Index Refractive Index is an optical characteristic of a substance and the dissolved particles within it. The refractive index of a substance is strongly inuenced by temperature and the wavelength of light used to measure it. Therefore, care must be taken to control or compensate for temperature dierences and wavelength. The refractive index measurements are usually reported at a reference temperature of 20 °C (68 °F), which is considered to be room temperature. Refractive index is dened as the ratio of the speed of light in a vacuum to the speed of light in a substance. A result of this property is that light will “bend,” or change direction, when it travels through a substance with a dierent refractive index. This is called refraction. When passing from a material with a higher to lower refractive index, there is a critical angle at which an incoming beam of light can no longer refract, but will instead be reected o the interface between the two substances. This is called total internal reection. The critical angle can be used to easily calculate the refractive index according to the equation: sin (Ĭcritical) = n2 / n1 Where n2 is the refractive index of the lowerdensity medium; n1 is the refractive index of the higher-density medium. A digital refractometer uses an LED to pass light through a prism in contact with the sample. An image sensor determines the critical angle at which the light is no longer refracted through the sample. Specialized algorithms then apply temperature compensation to the measurement and convert the refractive index to the specied parameter. 13 Refractometers 13.2 | www.hannainst.com introduction
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