Digital handheld refractometer
From Wikipedia, the free encyclopedia
In optics, a digital handheld refractometer is an instrument for measuring the refractive index of materials. 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 photodiodes creating a shadow line. The refractive index is directly related to the position of the shadow line on the photodiodes. 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 emulsions and other difficult-to-read fluids that form fuzzy shadow lines. 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 related to refractive index, and display a digital readout on an LCD or LED scale.
Digital handheld refractometers are generally more precise than traditional handheld refractometers. Users should look for instruments with a digital display that is capable of displaying not just a reading but also the unit of measure of the substance (Brix, freezing point, boiling point, concentration, etc.). A stainless-steel sample makes it easier to clean and an opaque cover over the sample area can prevent sample evaporation or ambient light from interfering with readings. Some instruments are available with multiple scales. It is important to select an instrument that can be set to distilled water and can also accept traceable calibrations at an upper span point.
[edit] Digital immersion-probe refractometers
A digital fiberoptic refractometer is presently available that works on an entirely different principle. This instrument is a probe type refractometer that is actually inserted into the fluid to be measured. A fiberoptic sensor determines the refractive index.
[edit] See also
- Refractometer Types
