Traditional Handheld Refractometer

A traditional handheld refractometer is an analog instrument for measuring a liquid's

refractive index In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium. The refractive index determines how much the path of light is bent, ...

. It works on the ''critical angle'' principle by which lenses and prisms project a shadow line onto a small glass

reticle A reticle, or reticule also known as a graticule, is a pattern of fine lines or markings built into the eyepiece of an optical device such as a telescopic sight, spotting scope, theodolite, optical microscope or the screen of an oscilloscop ...

inside the instrument, which is then viewed by the user through a magnifying eyepiece. In use, a sample is placed between a measuring prism and a small cover plate. Light traveling through the sample is either passed through to the

or totally internally reflected. The net effect is that a shadow line forms between the illuminated area and the dark area. It is where this shadow line crosses the scale that a reading is taken. Because refractive index is very temperature dependent, it is important to use a refractometer with automatic temperature compensation. Compensation is accomplished through the use of a small

bi-metallic strip A bimetallic strip is used to convert a temperature change into mechanical displacement. The strip consists of two strips of different metals which expand at different rates as they are heated. The different expansions force the flat strip to be ...

that moves a lens or prism in response to temperature changes. This design was invented by Emanuel Goldberg. There are many types of refractometers and the most common types are Abbe's refractometer, Pulfrich refractometer, Immersion refractometer. {{DEFAULTSORT:Traditional Handheld Refractometer Refractometers