Kemtrak Industrial Photometers & Turbidimeters

For applications requiring the measurement of the color, concentration, and/or turbidity of a liquid, South Fork Instruments relies on the Kemtrak 007 industrial photometer platform. This platform allows for the configuration of a wide range of state-of-the-art industrial optical analyzers designed to accurately measure and report specific properties of liquids and gases in-line, and in real time.

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Kemtrak is an industry leader in the development of photometers for any and all industrial applications.

The Kemtrak DCP007 is an industrial UV-VIS-NIR photometer designed to accurately measure the color and/or concentration of liquids. Real-time measurement results are in absorbance and can be displayed in standard units such as PCU (Pt-Co), Hazen, APHA, Saybolt, %wt and many others. The DCP007 uses a high-performance, long-life LED light source with robust industrial fiber optics to provide a measurement with very high precision. A proprietary dual-wavelength four-channel measurement technology allows accurate measurement of both highly colored and trace-color levels. Three variants are available, - UV, VIS and NIR. UV is used for concentration, VIS of color and NIR of water and trace water in solvents. Each analyzer has a primary absorbing wavelength to accurately measure the substance or color of interest. A second wavelength is used to compensate for solution turbidity and optical window fouling.

Since optical fibers are used to transmit the light energy to the measurement point and back, the measurement cell contains no electronics, moving parts or sources of heat. Standard measurement cells are manufactured in robust stainless steel and use sapphire windows to provide long and maintenance-free operation. Measurement drift caused by LED light source or filter aging is negligible, and once set, instrument recalibration is not required.

Where calibration is required, the Kemtrak DCP007 employs a simple automated QuickCal one-point and zero-calibration method suitable for the vast majority of applications.

What is a Photometer?

In-line photometers use light to provide real-time measurement of the color or concentration of components in a liquid (or gas) process stream. Photometers can be configured for a variety of purposes, with the configuration and technique used depending upon the specific measurements needed. Simply put, an industrial photometer is used to measure light after it has passed through an industrial process stream.

How does a photometer work?

Analytical photometry has been around for many decades with many earlier photometers offline units based upon visual standards. They utilized glass plates of specific colors that were compared stereoscopically to process fluid samples with the naked eye. As technology progressed, in-line analyzers using photodetectors were developed that measured light more accurately, repeatably and in real time.

The most common type of photometers, of which the Kemtrak DCP007 is a notable example, uses light absorbance techniques to determine and report the concentration of a particular component in a fluid stream. They can be configured to operate with broadband light, broad NIR, or a discrete wavelength in the UV, VIS, or NIR light regions depending upon the application. The Beer-Lambert law—which relates the reduction in intensity of light as it passes through a material to the concentration of the material absorbing the light—applies in this application. The optical path length must be configured to suit the expected absorbance measurement range.

Turbidimeters are often referred to as photometers, mainly because they are manufactured and supplied by absorbance photometer producers. In-line turbidimeters use scattered light, absorbance and backscattered light techniques to determine the amount of particulate or solid in a flowing stream.

What applications are photometers used for?

They measure process parameters such as color, concentration, turbidity, solids concentration and fluorescence. Each photometer consists of an advanced electronic unit, with a light bench constructed using high-performance light source technology, rugged industrialized fiber optic cables, and an in-line flow cell or probes with wear-resistant sapphire windows.

Photometers are used in many industries, including chemical, oil and gas, food and beverage, biotech, pharmaceutical and water. They are deployed where a specific property or constituent of the stream is to be monitored and used as a control variable in some way.

How are photometers installed?

The most common measurement flow cell for lightly colored applications, such as drinking water, is a long pass stainless steel Z-path cell, shown here with optional windows cleaning nozzles. The cleaning sequence can be fully automated using the inbuilt DCP007 controller software. Wastewater monitoring is typically higher colored samples and a shorter OPL measurement cell is required.

Kemtrak stainless steel long pass (OPL = 100mm) G 1” (DN 25) pipe thread measurement cell with optional G 1/8” (DN 6) sapphire window cleaning nozzles.

A typical measurement cell for this application is a 1” NPT type cell, like this Kemtrak stainless steel NPT 1” tapered pipe thread measurement cell with sapphire measurement window.

How can you get the best possible performance from a photometer?

Installation. Wherever possible, always install a photometer in a pipe where flow is vertically upwards. This will ensure the most homogenous sample is passing through the photometer light beam.

Flow conditioning. Aeration is the number one interfering factor in photometer performance. In absorbance systems, it makes measurement noisy and creates errors. In turbidity systems, gas bubbles look just like particulate matter, so readings become inaccurate and can be erratic. Suppressing aeration in the flow stream greatly improves the quality of the measurement.

Fouling compensation. Photometers use windows to introduce and extract light from pipelines. Over time, these windows can become contaminated with process material forming a film or layer on their surfaces. Mechanical cleaning devices or spray jets can help alleviate the problem, but make sure your photometer also has a means of electronically adjusting for window contamination so the measurement remains stable.

Instrument light decay. Today, LEDs are widely available and older style incandescent/gas discharge lamp photometers are essentially obsolete. Whatever the light source in your unit, make sure it has the ability to self-check and adjust the light output so that it remains constant. Changing light intensity looks like a change in measurement to a photometer and contributes greatly to drift.

Stray light. Incidental light getting into your photometer’s optical circuit can create havoc with the measurement. This is not usually a problem with metal pipe installations, but can be quite extreme when installing photometers in plastic or fiberglass pipes. Ambient light can travel through non-black materials and enter the light circuit. If you observe trends like measurements declining every time the sun comes out, you have an issue with light contamination. Install blackout material upstream and downstream of your sensor—it may be necessary to do so for quite a distance—to prevent ambient light from being a problem.

What color scale is used for measuring water color?

APHA, Platinum-Cobalt (Pt-Co) and Hazen are different names for the same color scale, which is specified by ASTM D 1209, BS5339:76 (1993), DIN 53409 and ISO 6271-1:2004(E). The APHA color scale measures the yellowness of a liquid, and is well suited for quality control and contamination detection. It is regularly used to evaluate pollution levels in wastewater and for drinking water quality control and regulation. The APHA scale can also be used to measure and control the concentration of iron in groundwater.

Originally a visual standard using glass slides to compare against process samples inside a stereoscopic viewer, APHA has evolved to being electronically measured with portable testers. A further evolution has moved measurements online so APHA color can be monitored in real time using photometers.

In-line instruments, such as the Kemtrak DCP007, use a measurement wavelength that is typically between 380 and 500nm depending upon the process color range to be monitored. Highly colored processes (> 500 APHA) require a short optical path-length (OPL) while lightly colored process streams (<100 APHA) require a long OPL. A reference wavelength of 650nm or 850nm is used to compensate for both turbidity in the process stream and window fouling over time. Optimum selection of wavelength and OPL is necessary for the best performance.

What are the benefits of using a NIST-traceable validation accessory?

The optional Kemtrak NIST-traceable validation filter holder permits the use of either NIST-traceable reference standards or liquid samples in order to quickly check instrument performance on a regular basis to ensure the photometer is operating within satisfactory parameters without having to remove the flow cell from the process line.

The validation accessory is supplied either fitted to the optical flow cell or as a standalone accessory in the optical fiber chain. The validation filter holder is designed to use industry standard 10mm cuvette style NIST-traceable absorbance filters, the same type as used on many standard laboratory spectrophotometers.

Benefits of using a Kemtrak NIST-traceable validation filter holder include:

Fast verification of measurement accuracy
Industry standard 10mm cuvette size
Same set of standard NIST filters as used in the laboratory
Cross validation between laboratory spectrophotometer and Kemtrak in-line industrial process photometers
Liquid samples can be measured
Recognized by international quality systems such as GLP, ISO 9000 and ISO/IEC 17025

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

South Fork Instruments is an industry leader in developing photometric analysis solutions for a wide range of industries.

For applications ranging from manufacturing and water analysis to groundbreaking scientific research, South Fork Instruments can assist you in developing cost-effective photometric measurement systems specially tailored to your needs.

What are the most common types of photometers?

All photometer designs are based upon a single operating principle: shining a beam of light into a sample of liquid or gas, and then measuring the changes in that light after it has passed through sample to calculate one or more variables.

Differences in materials and applications requires the use of different wavelengths of light and measurement techniques. Today, there are many types of photometers found in commercial and industrial applications, with the following being the most common.

Color & Concentration (VIS) Analyzers

Color and concentration photometers are used to measure the concentration and color of a particular sample. While often used for analysis in the food and beverage industries, color and concentration are critical measurements in the oil and gas and chemical industries as well. Color is often related to visual standard scales, such as APHA/Hazen and Saybolt. Many color scales are used in industrial applications, sometimes being very industry specific (such as ICUMSA color for sugar), so configuration of the analyzer to reproduce the visual standard online is very important. Concentration measurements range from simple solids concentration to specific chemical species within a line.

Typical applications for color analyzers include:

Product color control for QA/QC
Chemical concentration
Filtration bed monitoring
Ion exchange column monitoring
Leak detection
Contaminant detection
Dilution and dosing control
Interface detection

We favor the Kemtrak DCP007 photometer because it is designed to accurately measure color and concentration even in turbid or hazy flow streams. The unique referencing system used by Kemtrak analyzers removes the effects of solids suspended in the flowing stream to give a “true color” measurement. The DCP007 uniquely provides outputs for both color/concentration and solids/turbidity from the same unit, making it a true multifunction instrument.

The Kemtrak DCP007 achieves this by measuring at two wavelengths. A primary absorbing wavelength is used to measure the concentration of the chemical being monitored, while a non-absorbing reference wavelength is used to compensate for turbidity, air bubbles, and fouling. The DCP007 uses precision fiber optics to shine a precisely focused monochromatic light through the process medium and back to a photo-detector. The attenuation of the transmitted light beam caused by absorbing substances in the process medium is mathematically described by the Beer-Lambert law.

Applying the Beer-Lambert law, the concentration of the sample can be calculated thusly:

A = ε · l · c

Where:

A = absorbance ( = – log transmittance)
ε = molar absorptivity coefficient
l = optical path length
c = concentration of absorbing species

Addition and dosing of chemicals such as chlorine dioxide are easily controlled using the Kemtrak DCP007, as the uncertainty of measurement surrounding many other measurement methods is removed by the rock-steady performance of the unit in-line.

NIR Absorbance Photometers

NIR absorbance photometers are used to measure how much light is being absorbed at a specific near-infrared (NIR) wavelength by material in a specific solution. Using this tool, it is possible to determine the concentration level of the material. NIR absorbance photometers are used for measuring concentrations of water in organic solvents, either in trace amounts, as in ethanol production, or in bulk in beverage applications.

For such applications, South Fork Instruments develops measurement solutions using the Kemtrak DCP007-NIR. It is simple to use, and designed to detect and report trace and bulk water content in flows such as alcohol, ethanol, methanol, gasoline, and sugar solutions.

The DCP007-NIR generates stable levels of NIR wavelength light that is passed through the flow stream and measures intensity changes due to absorbance of that light from varying water content. A temperature input is also optionally available to allow compensation of the measurement to a standard temperature–removing variations due to temperature–if necessary for the application.

Two versions of the DCP007-NIR are available:

LED source: Bulk water content across a range of 0 to 100%
Thermopile source: Trace water content down to trace (ppm) levels

The analyzer can be connected to any one of the many styles of flow-through cells Kemtrak offers. For tank or large pipe applications, a third-party fiber optic probe can also be used, usually without any special configuration or calibration requirements.

Typical applications for the DCP007-NIR include:

Solvent concentration
Moisture content analysis
Alcoholic beverage content monitoring and control
Water in alcohol monitoring
Chromatography control (solvent mixing)
Residual solvent concentration in pharmaceuticals
Solvent recovery
Residual moisture concentration
Replace Karl-Fischer titration
Sugar concentration

NIR absorbance photometers are particularly useful for measuring the presence of water in solvents and alcohol. Water has a strong absorption throughout the entire NIR band with absorption peaks at approximately 1440nm and 1930nm.

1440nm is recommended for water measurements from 0-100% water with approximately 0.1% precision.
1930nm is recommended for trace (ppm) water measurements.

NIR is a preferred technique for accurately determining water in solvent concentrations, primarily because of the high degree of accuracy achievable due to the large difference between the water and solvent absorption. For instance, it is possible to accurately determine alcohol in water from concentrated solutions (100% alcohol) all the way down to trace amounts.

UV Absorbance Photometers

Like NIR photometers, UV photometers are used to measure the amount of light being absorbed by materials in solution at specific wavelengths. UV absorbance photometers are of particular use in biotechnological processes, where they are used to detect the presence of expressed protein molecules after separation.

For such applications, we use the DCP007-UV analyzer, an advanced dual-wavelength photometer designed to accurately measure absorbance in the UV region of the electromagnetic spectrum. Optical fibers are utilized to transmit light from a source within the DCP007-UV instrument through an in-line sample cell and back again to a sensitive detection system to calculate the concentration of many substances in real time. The absence of electrical power in the light transmission system allows sample cells to be fitted in hazardous areas without any concern for electrical certification and approval. The DCP007-UV is an excellent and cost-effective solution for measuring flow stream absorbance and concentration in a process environment in place of far more expensive scanning type analyzers.

Traditional UV photometers use mercury vapor lamps that continuously expose the process stream to high-intensity broad spectrum UV radiation and heat. This can result in destruction of valuable in-stream product and produce unknown and [potentially hazardous] breakdown products. Traditional UV photometers also suffer from systematic drift requiring constant adjustment due to optical filter erosion caused by high-intensity UV radiation from the lamp, as well as changing lamp output resulting from age.

The Kemtrak DCP007-UV process analyzer uses state-of-the-art LED light sources at the exact wavelength required for the analysis. Light reaches the process through precision fiber optics and is delivered with energy levels thousands of times less than that of a traditional UV photometer. The ultra-low modulated power UV LED light source in the Kemtrak DCP007-UV process analyzer does not systematically drift or expose the product stream to high levels of UV radiation and temperature. LED light sources are available at discrete wavelengths from 250nm to 400nm in the UV region, ensuring any specific wavelength requirement can be serviced.

A proprietary dual wavelength, four-channel measurement technique and advanced digital electronic design allows for deep UV absorbance measurement up to 5 AU (in a 1cm optical path length) at up to two discrete wavelengths. A selection of shorter optical path-lengths allows for even deeper absorbance measurements.

Zero-dead-volume hygienic measurement cells contain no electronics or moving parts and are well suited for hazardous environments. In-line verification and QA are made possible using an insertable cuvette style certified filter or liquid. This simple method utilizes the same traceable or prepared liquid standards used for laboratory benchtop instrumentation verification and calibration and provides a direct correlation to offline measurement techniques for added confidence in measurement.

Typical applications for the DCP007-UV include:

Chromatographic separation
Micro- and nano-filtration systems
Concentration of aromatic solvents

The DPC007-UV in-line process analyzer delivers measurement performance never before thought possible in an in-line UV analyzer, but at a price point similar to older, inferior systems.

Suspended Solids Analyzers

Commercial usage of suspended solids analyzers is particularly common in the food and beverage industry, where high solids concentrations are found in many applications. These instruments are equally applicable in any applications involving slurry or waste streams.

The Kemtrak NBP007 is a high-resolution backscatter photometer that revolutionizes the measurement of high concentration suspended solids. Many suspended solids analyzers in the market are limited to measurements in the range of 0 to 10% TSS (total suspended solids). Turbidity-based scatter instruments will work in concentrations up to approximately 1% suspended solids before high optical density blinds them. These limitations are overcome with the NBP007, and for the first time, operators can monitor and have complete control over their process at any concentration up to 80% solids.

Benefits of the Kemtrak NBP007 include:

0005% (~5 NTU) … 80% suspended solids
Zero maintenance
Proprietary NIR Measurement technique
Display in NTU, FTU, ppm, mg/l, g/l or %
Robust hygienic Triclamp probe or Ø12mm PG13.5 pH probe footprint immersion probe designed for CIP processes
Analogue output (0/4-20 mA)
Modbus (slave) over TCP/IP and Profibus (optional)
Local and web-based graphical user interface (TCP/IP)

The Kemtrak NBP007 is comprised of a high performance near-infrared photometer coupled to a precision fiber optic backscatter measurement probe, allowing for the accurate measurement of suspended solids from dilute to extremely high concentration. The NBP007 overcomes limitations associated with traditional turbidity based optical density instruments by utilizing a proprietary backscatter NIR measurement technology that can measure extremely high suspended solids concentrations.

A unique benefit of the Kemtrak NBP007 is that it will not go blind at high sample concentration. While other probes stop working at around 4,000 NTU/FNU (less than 1% solids by weight), after which the signal decreases and produces erroneous and misleading outputs, the output of the Kemtrak NBP007 continues to increase with sample concentration, ensuring a reliable measurement.

The Kemtrak NBP007 utilizes a robust industrial backscatter probe with a sapphire window in either a hygienic Triclamp connection or Ø12mm PG13.5 pH style probe. Fiber optics are used to deliver light to the measurement point and back; the measurement probe contains no electronics or serviceable parts.

Fluorescence (Oil-in-Water) Analyzers

Water, when contaminated with non-soluble hydrocarbons will become visually turbid or cloudy. This turbidity can be measured and is directly proportional to the concentration of these non-soluble contaminants present. There are a variety of trace oil-in-water analyzers available on the market using the well-known scattered light turbidity technique. This technique works well for any non-soluble oil contamination in clean water, but results can be greatly affected by entrained gas and solids present in the stream.

However, oil rich in polyaromatic hydrocarbons (PAH) will fluoresce when illuminated with ultraviolet light. Fluorescence occurs when a substance absorbs light at one wavelength then re-emits the light at longer wavelength.

Typical oils that fluoresce include fuel oil, crude oil, hydraulic oil and transformer oil. Each oil type has its own unique fluorescence intensity resulting from its specific polycyclic aromatic hydrocarbon (PAH) content, the most abundant of the main hydrocarbons present in crude oil and petroleum products. PAHs are excited using ultraviolet (UV) radiation and will fluoresce in the UV-visible wavelength range as shown in the diagram below. The fluorescent properties of an oil are dependent upon a number of factors, such as its composition, the proportion of aromatics present and the oils carbon structure.

The combined fluorescence from both dissolved and non-soluble oil-in-water can be measured and correlated to oil content. Entrained gas and solids present in the stream do not fluoresce, and thus do not affect the measurement.

Unlike most oil-in-water analyzers, the Kemtrak FL007 analyzer is unique in that it utilizes both fluorescence and turbidity measurements, using proprietary dual-wavelength ratio measurement techniques for continuous monitoring of trace oil and hydrocarbon contamination in water. This dual technique makes measurements more reliable, providing a higher degree of confidence in the reported results, while also providing operators with deeper insight into the amount of oil being discharged into the environment in real time.

Automatic compensation for color and optical window fouling prevents measurement drift and built-in advanced diagnostic functions provide a measurement quality indication and prompt for when maintenance such as cell cleaning is recommended to ensure trouble free operation.

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

The Kemtrak TC007 turbidimeter utilizes principles of light scattering to measure the presence of suspended solids.

The Kemtrak TC007 is an easy to operate industrial process fiber optic turbidimeter designed to accurately measure the concentration of light-scattering components. Measurements are real-time and in-line. Long-life solid-state LED lamps and precision fiber optics are used to provide drift and noise free measurement at very high precision.

The Kemtrak TC007 can be configured to use the nephelometric method of turbidity measurement in accordance with International Standard ISO7027:1999(E). In this mode, a proprietary algorithm mathematically combines the ratio of attenuated and scattered light to accurately monitor the turbidity of the sample. Automatic compensation of sample color and fouling of the optical windows ensures trouble-free operation.

Maintenance-free measurement cells with scratch-resistant sapphire windows have no electronics or moving parts, making the unit suitable for use in hazardous areas.

Benefits of the Kemtrak TC007 include:

Real-time in-line turbidity measurement
ISO 7027:1999(E) compliant
0.01… > 4000 NTU/FTU
Zero maintenance
Reliable and robust infrared LED lamp
Extensive range of robust fiber optic measurement cells
Analog output (0/4-20 mA)
Modbus (slave) over TCP/IP and Profibus (optional)
Local and web-based graphical user interface (TCP/IP)
Optional hazardous area enclosures available

What is a turbidimeter?

Turbidimeters are scattered light instruments which analyze the relative clarity of a fluid by measuring the light scattered by particulate matter in a fluid stream. The incident light must be made parallel (collimated), and the detector set to the side of this incident beam to capture light as it strikes particles and is diverted from its original trajectory. This technique is limited to lower levels of turbidity in a stream. Once that limit is reached, absorbance techniques can be used. Correspondingly, once the absorbance unit reaches its maximum detection level, backscattered light can be used.

Each technique has a relative sensitivity, and while there is a great deal of overlap between the techniques, it is important to select the right one for the application to get the best and most satisfactory results.

What is turbidity?

Turbidity is a measure of water clarity that applies to all types of water. It’s used to determine the cloudiness of water. The more cloudy the water, the more turbid. And the more turbid the water, the more likely you’ll get sick from drinking or bathing in it. Haze, as it’s often called, comes from particles suspended within the water. Certain particles are large enough that they settle quickly.

Smaller particles, or colloidal particles, might never settle. They pose the greatest risk to water quality. Turbidity can also be used to describe other substances, like plastics or glass. But for this article, we’re focusing on water.

How does measuring water turbidity contribute to public health?

In the ancient world, people used their senses to test water quality. Measurements included how the water looked and tasted. Romans brought fresh water into their cities through aqueducts. They understood the importance of protecting against water-borne diseases. Through the years, people adopted crude methods of filtration and boiling to help improve water quality. People soon realized that wastewater must be properly disposed of to improve health conditions. The first sewer systems were established in Britain in the 18th century. The scientific study of water quality has been around since the early 1900’s. In 1908, Jersey City, New Jersey became the first U.S. city to treat drinking water.

In the 1970’s legislation passed through Congress to set standards for drinking water quality throughout the U.S.

In the U.S., the Environmental Protection Agency (EPA) approves water quality standards. Factors vary from state to state.

Some of the most common factors include:

Acidity or pH
Color
Oxygen levels
Turbidity

Turbidity is often removed in treatment plants. They use sand filtration and settling tanks to lower the overall amount. There are also certain chemicals that lower amounts through chemical reactions. Levels change often and it’s important to continually monitor water clarity to ensure safe levels for drinking or recreational use.

What causes turbidity to change?

Turbidity is affected by a variety of factors, both natural and man-made. Particles found in water can be any combination of silt, dirt, bacteria, or chemicals. Agriculture is a common culprit. When farmers irrigate their fields, runoff causes abnormally cloudy water. Construction and mining areas have the same problem.

In open water, turbidity is influenced by phytoplankton and algae. In certain environments, high amount supports plants and animals that need low levels of light.

The higher the turbidity of a water source, the more likely it is to make people sick. Bacteria and viruses cling to the particles in water and can hide behind particles during treatment.

During rainy seasons, runoff into streams and rivers makes turbidity higher. When water treatment plants have to deal with more turbid water, they tend to have more mud and silt in their systems. Filters and pipes can become clogged. Strict measurement of turbidity throughout the treatment process can be critical to keeping water standards reasonable.

Levels are also important for environmental standards. When water sources are contaminated with agricultural runoff, the fish and water plants suffer. Cloudier water allows less light to reach the bottom. Less light means the native plant species can’t grow like they normally would. This affects the entire food chain.

What is the unit of measurement for turbidity?

The primary unit of turbidity measurement is a Nephelometric Turbidity Unit or NTU. This method measures how light scatters off the particles suspended in the water. NTUs are most often associated with ratings of drinking water.

The World Health Organization (WHO) states that drinking water should never be above 5.0 NTU (link opens PDF).

Another way to measure water clarity is with a Secchi disk. The Secchi disk is a black and white disk that is lowered into a deep body of water. When the disk is no longer visible, it’s measured in meters or centimeters. The Secchi disk is ideal for quick, water quality field tests of lakes and deep rivers.

How is a turbidimeter used to measure the turbidity of a fluid?

To give a more formal definition of turbidity, it is the measurement of scattered light that results from the interaction of incident light with suspended solids and colloidal materials in a liquid sample, which results in light rays being scattered and absorbed rather than transmitted straight through the sample. As light passes through a sample containing suspended solids, the particles will absorb the light energy, then re-radiate the energy in all directions. Particle shape, size, color and refractive index determine the spatial distribution of the scattered light by the particle. Particles smaller than the wavelength of light (e.g. bacteria) scatter light in equal intensities in all directions, while particles larger than the wavelength of light result in greater forward scattering.

Small particles measuring less than 1/10^th of the light’s wavelength scatter light symmetrically like this:

Medium-sized particles measuring roughly 1/4^th of the light’s wavelength scatter light in a more forward direction:

Larger particles, with diameters greater than the light’s wavelength, produce scattering that is extremely concentrated in a forward direction:

When turbidity is measured at right angles to the incident light beam, particle shape and size differences are eliminated, providing very sensitive measurement of light scatter by all particles in the sample. International Standard ISO7027:1999(E) defines the measurement of turbidity by light measurement at 90°.

The inherent flexibility of the Kemtrak TC007 turbidimeter and measurement cell allows for configuration in various modes dependent upon the type and turbidity range of sample being monitored.

What is attenuated detection?

What is backscattered detection?

What is ratio detection?

Ratio detection is recommended when optical window fouling or absorption of NIR light may occur. Both transmitted light and scattered light is measured and mathematically combined using a ratio algorithm to calculate the turbidity of the sample. Absorption and/or window fouling (assumed uniform) will appear in both the numerator and denominator of the ratio algorithm and cancel out.

Good sensitivity at very low turbidity down to 0.01NTU/FNU.
Complies with ISO7027:1999(E) using scattered light at 90°.
Compensation for sample color.
Compensation for optical window fouling.

In ratio mode, a signal quality parameter is available to indicate the degree of optical window fouling. Quality is measure of the amount of light reaching the detector, and if quality goes below 10%, cleaning is recommended.

When should a turbidimeter be calibrated?

Depending upon the measurement range, either a one, two, or three-point calibration should be performed according to the following guidelines (using a 10mm optical path-length measurement cell):

1 to 20 NTU/FNU: 1-point calibration at 20 NTU/FNU
1 to 200 NTU/FNU: 2-point calibration at 20 and 100 NTU/FNU
1 to 4,000 NTU/FNU: 3-point calibration at 20, 100, and 4,000 NTU/FNU

The recommend calibration procedure is dependent upon the geometry of the measurement cell. Please consult a Kemtrak representative if you plan to swap to a different size or style of measurement cell.

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

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Kemtrak Industrial Photometers & Turbidimeters

Kemtrak is an industry leader in the development of photometers for any and all industrial applications.

What is a Photometer?

South Fork Instruments is an industry leader in developing photometric analysis solutions for a wide range of industries.

What are the most common types of photometers?

The Kemtrak TC007 turbidimeter utilizes principles of light scattering to measure the presence of suspended solids.

What is a turbidimeter?

SOUTH FORK INSTRUMENTS IS COMMITTED TO SOLVING YOUR FACTORY AND PROCESS AUTOMATION CHALLENGES

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