Category: Education

Using filter cells to eliminate wavelengths associated with interfering gases is called positive filtering in the field of spectroscopy. You may think of this as filtering out all the wavelengths the instrument should not “care about.” In order for positive filtering to be completely effective, the analyzer must filter out all wavelengths associated with all interfering species. In some applications, this…

Non-dispersive analysis, while newer in discovery than dispersive analysis (Isaac Newton’s 17th-century prism), has actually seen far earlier application as continuous process analyzers. The basic design was developed during the years 1937-1938 by Dr. Luft and Dr. Lehrer in the laboratories of the German chemical company I.G. Farbenindustrie. By the end of World War II, over…

The dispersion of visible light into its constituent colors goes all the way back to the 17th century with Isaac Newton’s experiments, taking a glass prism and generating the characteristic “rainbow” of colors: A modern variation on the theme of a solid glass prism is a thin diffraction grating, causing light of different wavelengths to “bend” as they…

Light is known to interact with matter in very specific ways, which may be exploited as a means of measuring chemical composition. Either a sample of substance to be analyzed is stimulated into emitting light (optical emission), or made to absorb light from an external source (optical absorption). The specific frequencies (colors) of light obtained from these analyses…

Imagine a major marathon race, where hundreds of runners gather in one place to compete. When the starting gun is fired, all the runners begin running the race, starting from the same location (the starting line) at the same time. As the race progresses, the faster runners distance themselves from the slower runners, resulting in…

pH is the measurement of the hydrogen ion activity in a liquid solution. It is one of the most common forms of analytical measurement in industry, because pH has a great effect on the outcome of many chemical processes. Food processing, water treatment, pharmaceutical production, steam generation (thermal power plants), and alcohol manufacturing are just…

The electrical conductivity of liquids is an important analytical measurement in many industrial processes. This measurement is one of the more non-specific types of analytical technologies, because it does not discriminate between different conductive substances dissolved in the solution. For this reason, conductivity measurement is found in process applications where the type of conductive substance…

In the field of industrial instrumentation and process control, the word analyzer generally refers to an instrument tasked with measuring the concentration of some substance, usually mixed with other substances. Unlike the other “bulk” measurement devices for sensing such general variables as pressure, level, temperature, or flow, an analytical device must discriminately detect one specific substance while ignoring all…