Control Engineering explains the basics of process analysers and introduces two recently released products for the analysis of gas. When there is a need to monitor a process variable that extends beyond the 'big four' (pressure, flow, temperature, and level), some type of process analyser usually does the job. This category of instrumentation has its own big four subtypes: Composition - Detect and measure specific chemical components in the process stream; Electrochemical - Measure specific ion concentration, most commonly hydrogen (pH); Spectrophotometry - Use light absorbing characteristics to detect and measure specific components; and, Physical property - Measure specific gravity, density, viscosity, etc.
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