A digital handheld refractometer is an instrument for measuring the refractive index

Refractive index

In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

 of materials.

Principle of operation

Most operate on the same general critical angle principle as a traditional handheld refractometer

Traditional handheld refractometer

A traditional handheld refractometer is an analog instrument for measuring a liquid's refractive index. It works on the critical angle principle by which lenses and prisms project a shadow line onto a small glass reticle inside the instrument, which is then viewed by the user through a magnifying...

. The difference is that light from an LED

LEd

LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

 light source is focused on the underside or a prism element. When a liquid sample is applied to the measuring surface of the prism, some of the light is transmitted through the solution and lost; while the remaining light is reflected onto a linear array of photodiodes creating a shadow line. The refractive index is directly related to the position of the shadow line on the photodiodes. Once the position of the shadow line has been automatically determined by the instrument, the internal software will correlate the position to refractive index, or to another unit of measure

Unit of measure

Unit of measure may refer to:* Units of measurement for relevance to weights and measures* Unit of account for relevance in economics* Unit of Measure , a 2000 album by Tony Rice...

 related to refractive index, and display a digital readout on an LCD or LED

LEd

LEd is a TeX/LaTeX editing software working under Microsoft Windows. It is a freeware product....

 scale.

The more elements there are in the photodiode array, the more precise the readings will be, and the easier it will be to obtain readings for emulsion

Emulsion

An emulsion is a mixture of two or more liquids that are normally immiscible . Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion is used when both the dispersed and the...

s and other difficult-to-read fluids that form fuzzy shadow lines.

Digital handheld refractometers are generally more precise than traditional handheld refractometers, but less precise than most benchtop refractometers. They also may require a slightly larger amount of sample to read from since the sample is not spread thinly against the prism.

The result may be displayed in one of various units of measuremeant: Brix

Brix

Degrees Brix is the sugar content of an aqueous solution.One degree Brix is 1 gram of sucrose in 100 grams of solution and represents the strength of the solution as percentage by weight . If the solution contains dissolved solids other than pure sucrose, then the °Bx is only approximate the...

, freezing point, boiling point, concentration, etc. Nearly all digital refractometers feature Automatic Temperature Compensation (for Brix at least)

Most have a metal sample well around the prism, which makes it easier to clean sticky samples, and some instruments offer software to prevent extreme ambient light from interfering with readings (you can also shade the prism area to prevent this as well). Some instruments are available with multiple scales, or the ability to input a special scale using known conversion information.
There are some digital handheld refractometers that are IP65 (IP Code) water-resistant, and thus washable under a running faucet.

See also

• Refractometer Types
  • Traditional handheld refractometer
    Traditional handheld refractometer
    A traditional handheld refractometer is an analog instrument for measuring a liquid's refractive index. It works on the critical angle principle by which lenses and prisms project a shadow line onto a small glass reticle inside the instrument, which is then viewed by the user through a magnifying...
    
    
  • Abbe refractometer
    Abbe refractometer
    An Abbe refractometer is a bench-top device for the high-precision measurement of an index of refraction.- Details :Ernst Abbe , working for the Zeiss Company in Jena, Germany in the late 19th century, was the first to develop a laboratory refractometer...
    
    
  • Inline process refractometer
    Inline process refractometer
    Inline process refractometers are a type of refractometer designed for the continuous measurement of a fluid flowing through a pipe or inside a tank. These refractometers typically consist of a sensor, placed inline with the fluid flow, coupled to a control box...