Kemtrak Turbidimeters

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 hazardous area use.


  • 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 & Profibus (optional)
  • Local & web based graphical user interface (TCP/IP)
  • Optional hazardous area enclosures available

Is Kemtrak Right for Your Application?

Let Kemtrak give you a solution – download an application data sheet, fill in your process specifications and send it to us. We’ll come back to you with a configuration that will suit your needs.

Advanced Feature Summary

Why Kemtrak turbidimeters? A comparison of some of the features and advantages of a Kemtrak Inline Turbidimeter over traditional turbidimeters

 Kemtrak Inline TurbidimeterTraditional Inline Turbidimeter
Light SourceMonochromic LED light source
Light level constantly controlled at the same level
Light output quality does not degrade
Unlimited life - 100,000's of hours
Runs cold
Broadband incandescent filament lamp
No real-time light output control
Lamp temperature changes over time - measurement drift
Limited life - 5000 - 10000 hours
Generates a lot of heat
Light DetectorsSilicon Photodiodes
Dark current changes with temperature. Analyzer measures dark current and adjusts accordingly - no drift/offset
Mounted in analyzer case away from the process line
Silicon Photodiodes
Dark current changes with temperature - not adjusted by electronics - measurement drift/offset
Mounted at line - poor environment for sensitive component
ElectronicsAll electronic components in the analyzer case. Stable temperature - stable performance
Fiber optics between analyzer and inline cell. Failure risk very low
Broad range of detailed diagnostics including signal quality, light source drive power, signal gains, light leakage/stray light indication and a full deck of instrument health parameters
Distributed between transmitter and sensor. Sensor temperature changes with process - introduces error
Requires wiring and electrical connectors at the process line - risk of failure high. Wires in process area susceptible to noise pickup from other wiring
Diagnostics limited to lamp fail indication
In line flow cellVery small housing - no electrical or optical components at line.
Completely suitable for hazardous area installation - light only.
90 degree scattered light method easy to implement. Mimics offline laboratory test readings and method.
High temperature applications possible
Large housings to accommodate electrical components and optical bench
Difficult in hazardous areas - special housings required
Large sensor housings dictate the use of forward scatter technique - not equivalent to most offline measurement techniques: lack of correlation of process to offline laboratory/test readings
Temperature limited by components in flow cell housing
Optical benchMonochromatic light source - minimal filtering required. Filters remain stable - no high temperature light source to damage them.Requires significant filtering to establish wavelength required and block out of band stray light. Filters in intimate contact with the light source degrade over time due to heat
I/OAnalog outputs, Modbus over IP, remote TCP/IP HTML Interface (access using standard web browser - includes complete on-board user manual)Standard analog outputs, proprietary serial protocol for communications

Technology Overview

Measuring Principle
Kemtrak TC007 Turbidimeter

Turbidity is the measurement of scattered light that results from the interaction of incident light with suspended solids and/or colloidal materials in a liquid sample that causes light rays to be 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 a greater forward scattering.


Small particles (< ⅟10th wavelength light) scatter light like this:turbidity 1

Medium particles {ca. ¼ wavelength light) scatter light like this:turbidity 2

Large particles (larger than wavelength light) scatter light like this:
turbidity 3

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:


1) Attenuated Detectionturbidity 4


This detection methodology measures the attenuation of the incident light by a detector positioned in-line with the incident light beam.

  • Results correlate well to the concentration of suspended solids
  • Can be zeroed between runs to compensate for optical window fouling
  • Large concentration range determined by the optical path length

2) Backscattered Detectionturbidity 6

Backscattered light can be measured using a Kemtrak backscatter probe and allows the accurate measurement of suspended solids from dilute to extremely high concentration solutions.

  • Good sensitivity from 20 NTU/FNU to extremely high concentrations
  • Uses robust backscatter probe


3) 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.


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

01- 20 NTU/FNU1-point calibration @ 20 NTU/FNU
01- 200 NTU/FNU2-point calibration @ 20 & 100 NTU/FNU
01- 4 000 NTU/FNU3-point calibration @ 20, 100 & 4 000 NTU/FNU

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