Guided Wave Now Offers Optical Solutions© UV/VIS/NIR SMART Photometers™

Optical Solutions pioneered multiple-wavelength, no-moving-parts filter photometers for on-line, real-time chemical measurements of liquids and vapors. They developed such innovations as simultaneous measurements of visible color and near-infrared chemical composition, and incorporated SMART Photometer© technology to minimize guesswork in after-installation support, including unique chemical outlier detection alarms. The patented technology is based upon simultaneous measurements of all wavelengths to minimize process-induced noise and to avoid maintenance with moving filter wheels. They developed the means to bring sample temperature into the calibration in real time. They expanded the product line into the UV and added the ability to measure multiple sample points from one analyzer. They developed a simple user interface suitable for instrument specialists at the plant, including calibrations that could be developed in and imported from Microsoft© Excel©.

They developed Step-Up™ technology where the customer can prove an application at the plant with a NEMA 4X ChemView and have the ChemView incorporated into a multipoint ChemViewMx at a later date using the same calibration models for only a hardware upgrade charge. NEMA 4X, Class 1, Divisions 1 and 2, Groups B-D and ATEX enclosures.

These lower-cost, easy-to-use process photometers, are perfect where the application does not demand complete spectral analysis and chemometrics multivariate calibration methods.

The Products

ClearView • Single point • No-moving-parts • Prices starting at $13,000 • Up to 3 analyzing wavelengths measured simultaneously • Color + Chemistry • 400-1650 nm • 3 4-20 mA outputs Saybolt/ASTM color or red dye in fuel, % water in organics and acids, solvent recovery, simple vapor mixtures such as ethylene in ethylene dichloride, NTU turbidity with special light-scattering probe.

ChemView©

• Single point • No-moving-parts • Prices starting at $23,000 • Up to 5 analyzing wavelengths measured simultaneously • UV/VIS 250-1000 nm • VIS+NIR 400-2150 nm • Chemical outlier detection • 6 4-20 mA outputs

UV chlorine gas or chlorinated hydro-carbons, ppm moisture, complex organic mixtures, caustic, acid and hydroxyl numbers in resins and polymers, color + NIR, possible substitute for spectro-photometer for PLS models with <4 factors.

Simulplex ChemView©

• 2 sample points • No-moving-parts • Prices starting at $28,000 • UV/VIS 250-1000 nm, or • VIS+NIR 400-2150 nm • Chemical outlier detection • 4 analytical wavelengths divided between the 2 sample points measured simultaneously with a reference wavelength for each • Simultaneous output • 6 4-20 mA outputs

Ideal for monitoring 2 points on a distillation column – before and after the reaction, or two adjacent process lines to avoid the cost, lag time and reliability of sample switching, such as reverse phase chromato-graphic separation of water and acetontirile in pharmaceutical processing.

ChemViewMx

• Up to 8 sequential sample points using reliable fiber optic mulitplexer • Prices starting at $48,000 for 4 sample points • Up to 5 wavelengths at each point measured simultaneously • UV/VIS 250-1000 nm, or • VIS+NIR 400-2150 nm • Chemical outlier detection • Contact closure or RS232 sample point sequencing • Step-Up™ Technology • 6 4-20 mA outputs

Applies ChemView technology sequentially at up to 8 sample points up to distances of 100 m. An important application is end-of-reaction determination in resin batch reactors at high (250 C) temperatures, where acid and hydroxyl numbers, ppm water and yellow color are monitored simultaneously within each reactor.

How Photometers Work

Unlike spectrophotometers that analyze the entire spectrum, photometers are "tuned" for each application with several wavelengths that were defined from an analysis of the complete spectrum.

The spectral unit of absorbance is used in the photometer at the "analytical" wavelength(s) where the species of interest absorbs light, e.g. 1440 nm for %water. An absorbance measurement is always referenced to another wavelength that is not affected by concentration changes. In the NIR, this is typically 1050 or 1300 nm. This latter wavelength is referred to as the "reference" wavelength. ChemView and ClearView technologies use beamsplitters to divide the light returned from the sample among separate detector/filter combinations for each wavelength. The voltage from an analytical wavelength detector is ratioed to that from the reference detector, a logarithm is taken and the result is absorbance at the analytical wavelength. Coefficients are applied to the absorbances to determine concentration that is then output on isolated, self-powered 4-20 mA outputs to your process control computer.

What Does "SMART Photometers" Mean

The development of these products focused upon lowering after-installation maintenance and support. The goal is to minimize guesswork during troubleshooting. The "reference" voltage is used as a "lightmeter" and is also trended as a primary signal during troubleshooting to diagnose hardware faults, such as:

Optical fiber breakage

Window coating

Intermittent turbidity

Lamp failure

Our patented Outlier Detection optionally used with more than one analyzing wavelength lets you know if you have a sample that does "fit" within the range of samples used to calibrate the analyzer. These are based upon Chemometrics parameters, referred to as the Mahalanobis Distance, M, and the Sum of Squares statistic, Q. These can be trended or they can be used as a discrete alarm. Thus, we can help you distinguish the difference between a hardware problem and a possible chemical contaminant in your process.

Photometer Performance

ChemViews and ClearView have a patented optical stabilization feedback circuit that keeps the lamp intensity constant as the lamp ages. Lamp stabilization plus extensive internal thrermostatting leads to very low photometric drifts of ~2 mAU over a 2-3 week period. Precision for an on-line analyzer depends upon its photometric drift. This converts into approximately +/- 40 ppm water measured in a 2 cm optical cell at 1900 nm.

Interactive CD-ROM Training Manual

ChemViews and ClearViews can be supplied with interactive DVD training manuals that operate like a web site. This makes it easy for busy instrument technicians to select just the fix they need to solve a troubleshooting problem, including movies showing how to change a lamp and re-zero the analyzer, for example.

Photometers or Spectrophotometers

Our combined team of experts at Guided Wave can help guide your selection. In general, it should be assumed that photometers are dedicated instruments for a specific application. They are spectrally "tuned" to that application and thus, are not likely be useful for a completely different application. Although this decision is application-specific, here are some generalized reasons why a photometer may be chosen over a spectrophotometer for liquids and vapors:

Budget constraints

Lower in-house expertise available for calibration support

Dedicated applications

Production vs. R&D in a pilot reactor

Fewer chemical components need to be measured at each sample point

Applications where chemometrics analysis of spectrophotometer data requires < 4 factors