Online Turbidity Meter

Online Turbidity Meter – TurbSense®

Online Turbidity Meters from Pi are called TurbSense® and include analyzers, controllers and monitors which determine true online turbidity and/or suspended solids in water, using a nephelometric measurement of scattered light in accordance with ISO 7027. The TurbSense® sensor uses LED optical technology to provide an extremely stable, accurate, low maintenance sensor.

The TurbSense® online turbidity meter is a breakthrough in measurement technologies in that it automatically varies the light output so that the turbidity can be measured independently of background light and electronic drift.

Ranging from 0.01 NTU to 1000 NTU with a resolution in the 0-10 NTU range of 0.001, the TurbSense online turbidity meter provides:

  • Excellent resolution
  • Single point calibration
  • The simplicity of a probe
  • Great value for money
  • Long term reliability
  • Autoclean so very low maintenance

Turbidity Meter Flow Cell

Debubbling Flow Cell – TurbSense®

Each probe is equipped with a light source, a side detector for the measurement of scattered light from the sample and a reference detector for monitoring the light output. The light source is a long-life IR LED emitter. This configuration allows accurate and reliable measurements of online turbidity and suspended solids to be made. Reliable calibration can be carried out using a single calibration with no need for a ‘zero’.

The probes are constructed of stainless steel and sapphire so can withstand demanding operating environments. An Autoclean system can be included to keep the optical surfaces clean, thereby reducing maintenance to a potential ‘maintenance free’.

The TurbSense® online turbidity meter is suitable for dip monitoring and mounting in a debubbling flow cell.

The operating principle of the online turbidity meter is subject to a patent application and is unique in the way it handles the data it receives in order to calculate a zero, to calibrate and to derive the NTU (FNU) value from the readings.

Turbidity Meter installation at Kilva

Online Turbidity Meter Installation at Kilva

  • Autoclean solid state optical sensor – no moving parts
  • Single point calibration – very easy to use
  • Stable and reliable – excellent process control
  • Suitable for all potable, waste and process waters between 0 NTU and 1000 NTU
  • ‘Maintenance free’ – low cost of ownership
  • No ‘zero’ required – improved accuracy at the low end
  • Up to 1 year between calibration – very little drift
  • Up to 10 bar – for inline operation
  • 0.001 resolution
  • Automatic debubbling and bubble removal solutions – no interference from bubbles

The TurbSense® online turbidity meters are available with different controllers giving you the same great performance with different communication, display, and control options. With the TurbSense® range of online turbidity meters, you get everything that you need – and nothing that you don’t, without sacrificing the quality of the measurement.

The online turbidity meters from Pi are now in use around the world providing trouble free, easy to use solutions to a range of online turbidity monitoring and control.

TurbSense turbidity meter compared to sample turbidity.

Comparison between sample turbidity and turbidity measured with TurbSense® with a wide range of turbidities.

Anywhere where the measurement range is 0.01-1000 NTU (approx 0-2000 mg/l, application dependent) is a suitable application for the TurbSense® online turbidity meter.

Traditional online turbidity monitoring applications where the TurbSense® is particularly suited:

  • Raw water inlet
  • Settled water turbidity
  • Final water turbidity
  • Waste water effluent turbidity
  • Fire hydrant monitoring
  • Swimming pool clarity monitoring
Water Treatment PlantSmall water treatment plants, secondary disinfection plants etc. tend to suffer from similar problems wherever they are in the world. The first is lack of communications SCADA infrastructurs, the cost of which to install can be prohibitive. The second is the lack of a central DCS control infrastructure, again the installation of which can be cost prohibitive. The third is the remote location. Often these water treatment plants are in remote and difficult to access locations.

With these three issues facing many water engineers around the world, a low cost solution providing solutions to all three issues is available from Pi. A CRIUS® controller has the on board capacity to provide small scale SCADA, and full online PID control whilst the sensors (e.g. chlorine, pH, turbidity etc.) are suitable for long term operation without operator intervention.

To demonstrate the remote access capability of the CRIUS® please click here.

To learn more about the control capability of the CRIUS® please click here.

To hear more about other customers using the CRIUS® multiparameter controllers in a similar way why not contact us?

Document Type Size
TurbSense® Brochure 622kB
TurbSense® Calibration Article 726kB
US Turbidity Trial Article 661kB
Bubbles in Turbidity Measurements Technical Note 490kB
Turbidity Issues To Overcome Technical Note 650kB
CRONOS® Brochure 609kB
CRIUS® Brochure 734kB
CRIUS® Remote Communications Brochure 573kB
CRONOS® and CRIUS® Control Options Technical Note 534kB
Remote Access GPRS Technical Note 481kB

Turbidity is a measurement of ‘cloudiness’. Suspended solids is a ‘unit per volume measurement’ e.g. 1 mg of suspended solids in 1 litre of water.

Turbidity Meter in Calibration Chamber

TurbSense® Calibration Chamber

There are two ways to calibrate almost any sensor and TurbSense® is no exception.
The first is to use another device, such as a handheld portable turbidity meter to determine the turbidity of the sample that the TurbSense® is monitoring.
The second is to put the TurbSense® into a sample with a known turbidity.
Normally you would need to also put the other online turbidity sensor into a ‘zero’ to give the sensor two points to draw a calibration but the TurbSense® uses some fundamental laws of optics to make that zero unnecessary (patent applied for).

Sapphire is used for the windows as it is tough and scratch resistant (much more than glass or quartz). Its use also allows the windows to be thin (because it’s stronger) and therefore have good optical transmission.
The maximum temperature of the sample being monitored is 50°C. We choose 50°C because it is well within the upper limits of the electronic components that we use and still gives a good range or temperature for measuring online turbidity.
You can if the turbidity is high enough or the pipe is big enough.
To achieve a high level of performance the TurbSense® uses a powerful light source and sensitive optics. This means that in a pipe, reflections from walls and bends can cause inaccurate readings. The higher the turbidity, the closer the reflective surfaces can be so that at >200NTU putting the TurbSense® online turbidity meter in a pipe should be no problem.
For optimum performance fit an Autoclean unit to the sensor. This can be used to periodically clean the sensor window to ensure the highest accuracy in readings. Try to avoid placing the sensor in direct sunlight as the sensitive optics can pick up infra-red light emitted by the sun.
The flow chamber removes entrained bubbles to prevent them causing an interference to measurements. Its black polypropylene construction eliminates stray light and the lid removes ambient light, both potential sources of interference in measurements. For more details, please see our Technical Note, Bubbles in Turbidity Measurements.

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Karen Thirlwell

Head Office Contact