Like all tools, refractometers are available in a variety of models. Let’s take a look at the principal ones:
This convenient and portable design is one of the most widely used refractometer models. A lens and the internal prisms create a line marking the measuring point (the critical angle) on an internal reticule (arrangement of crosshairs). Viewers note the measurement via a small magnifying glass.
Digital refractometers work on the same principle as handheld models but are software-based, using light from an LED focused on the usual prism. When the sample liquid is applied, some of the light which passes through this will hit a number of light-sensitive diodes to create the measurement line, which is known as the shadow line. This line is then matched to a particular refractive index for display via an LED screen.
Brix refractometers are focused on this particular metric. Degrees of Brix (°Bx) indicate the quantity of sucrose in a solution - one degree is equivalent to one gram of sugar per 100 grams of solution. Brix refractometers are widely used in brewing and often offer a dual scale with parallel SG (specific gravity) readings to measure density.
Portable Optical Refractometers
Portable optical refractometers are typically used to measure the presence of dispersed oil in a number of emulsions and solutions that require precise mixtures to work properly and to avoid corrosion and hazardous fumes. Examples include the coolant used in industrial cutting and grinding machines.
These are larger, heavier duty models designed to quickly process multiple measurements. They are typically used near the production line in factories, in chemical storage areas, and in laboratories.
Named for Victorian physicist Lord Rayleigh, these models are now used principally for measuring the refractive index of gas. This is one of the earliest refractometer designs still in use.
These models are designed to take entirely automatic readings of liquids, gels, and other translucent substances, removing the need for users to manually assess a reading and translate this into the desired metric. They offer greater speed and accuracy than manual refractometers and often a wider selection of metrics as well.
Automatic refractometers are used in food processing to measure sugar and alcohol content, in industrial settings to verify solvent purity, and for medical and veterinary purposes.
Dual Scale Refractometer
Dual scale refractometers offer two parallel sets of metrics on their scales. A frequently seen example is those used in brewing which includes both degrees of Brix and specific gravity on their scales. Users can choose either metric when taking a reading.