A digital handheld refractometer is an instrument for measuring the
refractive index
In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
of materials.
Principle of operation
Most operate on the same general ''critical angle'' principle as a
traditional handheld refractometer. The difference is that light from an
LED 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
photodiode
A photodiode is a semiconductor diode sensitive to photon radiation, such as visible light, infrared or ultraviolet radiation, X-rays and gamma rays. It produces an electrical current when it absorbs photons. This can be used for detection and me ...
s 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
A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can ...
related to refractive index, and display a digital readout on an
LCD or
LED 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
An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...
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, 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
The IP code or International Protection code indicates how well a device is protected against water and dust. It is defined by the International Electrotechnical Commission (IEC) under the international standard IEC 60529 which classifies ...
) water-resistant, and thus washable under a running faucet.
See also
*Refractometer Types
**
Traditional handheld refractometer
**
Abbe refractometer
**
Inline process refractometer
References
{{DEFAULTSORT:Digital Handheld Refractometer
Refractometers