Glossary of density and concentration measurement
What does a reading tell you about your product? This glossary explains twelve terms covering density, concentration and microwave measurement. Illustrative calculations and practical guidance show which information matters when selecting and checking a measurement.
Measured quantities and fundamentals
Brix (°Bx)
The Brix scale refers to sucrose in water. In such a solution, 12 °Bx represents a 12% sucrose mass fraction. If a product contains other dissolved substances, a Brix display cannot simply be read as its pure sugar content.
Concentration
A concentration value describes how much of a selected component a mixture contains. Its basis matters: g/l relates component mass to mixture volume, while mol/l relates amount of substance to volume. A percentage also needs a stated basis, such as mass fraction.
Density
How much does a given volume of material weigh? Density answers this by dividing mass m by volume V: ρ = m / V. Typical units include kg/m³ and g/ml. Both quantities must refer to the same sample.
Pulp consistency
In papermaking, pulp consistency usually refers to a dry-material fraction in a fibre-water mixture, commonly expressed as mass percent. It differs from physical density, which relates mass to volume. The precise definition used by the mill must be established.
Total solids (TS)
Total solids determination asks how much of a sample remains after an agreed drying procedure. When reported as a mass fraction, TS equals dry residue mass divided by original sample mass, multiplied by 100%. The result must be accompanied by the method used.
Measurement methods and installation
Inline and online measurement
Inline and online answer different questions. Inline describes the measuring location: the sensor encounters the material directly in the process, for example in a pipe. Online describes an automated connection to operation and may also involve a connected sample line.
Microwave density measurement
Microwave density measurement uses a material’s response to an electromagnetic signal as measurement information. A suitable relationship converts that response into density. This is an indirect determination rather than a separate weighing of the product.
Microwave transmission
Transmission means that a microwave travels through the product along a measuring path. A receiver detects the arriving signal. Its strength and phase may differ from the transmitted signal, providing information about the interaction between the wave and the material.
Multifrequency technology
A multifrequency measuring system examines material at several microwave frequencies. This provides different signal observations for joint evaluation. The particular measurement and evaluation method determines how these observations contribute to a process value.
Calibration and process conditions
Calibration
Calibration gives a measuring system’s indication a documented relationship to known reference values. Indication and reference are compared under described conditions and their relationship evaluated, including uncertainties. Changing the instrument setting afterwards is a separate step: adjustment.
Suspension
A suspension contains solid particles distributed through a liquid. They remain a separate solid phase rather than being dispersed at molecular level as a dissolved substance. Whether they remain suspended or settle depends on particle size, density difference and movement of the material.
Temperature compensation
A reading may change as temperature rises or falls even when the target product quantity stays constant. Temperature compensation accounts mathematically for a described temperature effect, using temperature information and a relationship suited to the product.