Process Photometers

Process Photometers

Process photometers perform inline optical measurement using UV absorption, NIR, VIS, and related photometric techniques to quantify concentration, color, optical density, and turbidity. These instruments are designed for continuous, compliant measurement in process environments, often with hygienic mechanical design and robust stability under elevated temperature and pressure conditions.

Inline photometry reduces reliance on manual sampling and off-line lab testing, enabling faster control response and lowering contamination risk. Because photometric methods can operate without reagents, they can deliver low cross-sensitivity and reduced consumables burden while maintaining strong repeatability for quality monitoring and process optimization.

Absorbance measurement follows the Lambert–Beer relationship: light is transmitted through the medium and the detector measures the remaining intensity at a selected wavelength, converting the result to absorption units or optical density. Turbidity variants use scattered-light methods for monitoring filtration and solids behavior. Wavelength selection is matched to the measurement objective, such as NIR absorbance for cell growth measurement or dual-wavelength approaches for color measurement.

Applications include chromatography, fermentation, filtration, phase separation, crystallization, condensate monitoring, and leak detection of heat exchangers. Photometric turbidity measurements are also applied for filter control, and hazardous-area approved devices support deployment where flammable atmospheres require certified instrumentation approaches.

Design considerations include flow-cell geometry and path length, response time needs, and calibration strategy. Certified, traceable optical filters can simplify calibration compared with liquid standards, and low-volume flow cells can improve responsiveness and yield. Photometers are frequently combined with complementary measurements (pH, conductivity, oxygen) on unified transmitter platforms to consolidate hardware and improve data coherence.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.