Process Photometers

Process Photometers

Process photometers are inline optical instruments used for UV absorption, NIR, VIS, and turbidity measurements to deliver precise, compliant concentration, color, and turbidity monitoring without reliance on manual sampling. Their hygienic design supports demanding bioprocess and pharmaceutical workflows, and their temperature/pressure stability supports deployment in harsher utility and process services where safety and reliability are critical.

These devices apply well-established optical principles. Absorbance measurement is based on the interaction of introduced light with the medium according to the Lambert–Beer law: a defined wavelength passes through the process, a detector measures transmitted intensity, and the transmitter converts the signal into absorption units or optical density. For turbidity, scattered-light methods (including forward scatter at 11° for low turbidity) detect particle-driven light deflection and can identify filter breaks rapidly, supporting filtration monitoring.

Benefits include true inline measurement that reduces time spent sampling and measuring in a lab and helps prevent product contamination. The optical principle typically avoids reagents and offers low cross-sensitivity to unrelated parameters, while certified calibration filters (including NIST-traceable options) reduce calibration complexity versus liquid standards. Low-volume flow cells enable fast measurement response and can support yield optimization by minimizing hold-up volume and exposure time.

Application examples include chromatography, fermentation, filtration, phase separation, and crystallization - where optical signatures correlate to concentration, purity, or cell growth - and utility or reliability use cases such as condensate monitoring and heat exchanger leak detection. Selection is driven by wavelength choice (for example NIR absorbance for cell growth or dual wavelength for color) and by choosing the appropriate turbidity method for the expected particle regime and turbidity range.

Integration is often streamlined through multiparameter transmitter platforms. Process photometers can be combined with other liquid-analysis sensors (such as pH, conductivity, or oxygen) using a single transmitter architecture, enabling cohesive quality monitoring “packages” with shared infrastructure, consistent diagnostics, and a unified calibration and maintenance framework.

At Eastern Controls, We are proud to be the exclusive authorized sales and service representative for Endress+Hauser.