Why does the market need another turbidity sensor when so many are already available?

The simple answer to this question is that current sensors cannot overcome all of the common issues relating to online turbidity measurement. Pi’s patented TurbSense^® has a solution for all these problems.

Did you know that…

…the TurbSense^® uses a patented measurement method which means background light and electronic drift have no effect?
…Pi’s TurbSense^® provides a resolution of 0.001NTU up to 1000NTU using a single point calibration with no zero required?
…the TurbSense^® flow cell ensures the measurement is unaffected by both entrained and nucleated bubbles?

The problems with turbidity sensors and the TurbSense^® solutions

Bubbles

All turbidity sensors are severely affected by bubbles because they affect the optical properties of the water they are in. To a sensor these bubbles look like turbidity. Bubbles can become entrained in the sample water and, when pressure is reduced, dissolved gases in the water can also nucleate on any surface as bubbles, including the sensor window. Both nucleated and entrained bubbles can result in erroneous readings, affecting the reliability of the measurements.

Pi’s CRONOS^® and CRIUS^® TurbSense^® can utilize a flow cell, in which the sample flow passes through a baffle system, forcing the entrained air out of the sample. Furthermore, the TurbSense^® can regularly drop the level of the water in the flow cell, causing any nucleated bubbles on the sensor to burst. These simple, yet highly effective features ensure the turbidity sensor is free of interference due to entrained and nucleated bubbles.

Calibration

Most nephelometric turbidity analyzers either need a ‘factory set’ zero which can drift over time or a ‘zero NTU’ sample to determine the ‘zero’ during a calibration. It is almost impossible to source a ‘zero NTU’ sample due to the ease of contamination, so determining the ‘zero’ of a turbidity analyzer is a big problem… but not for the TurbSense^®!

Pi’s CRONOS^® and CRIUS^® TurbSense^® has a very clever and simple calibration system, removing the need for a ‘zero’. Pi’s TurbSense^® takes advantage of the linear nature of 90° nephelometric turbidity to determine the zero. By halving the output light from the sensor the TurbSense^® halves the detected light at a constant turbidity. Therefore, the zero can be back calculated which removes any drift and ensures the most accurate zero achievable.

To see a technical discussion on the measurement techniques employed by the TurbSense^®, click here.

Fouling of optics

Turbidity probes are used in a wide variety of water applications from potable to wastewaters. In many applications, the sample water can contain materials which can foul the optics preventing consistent accurate measurements. Both particulates and bubbles could partially or completely block sensor optics. Taking the sensor out of a sample to manually clean is an inconvenience to an industrial process as it may need shutting down to do this. Pi’s TurbSense^® ensures fouling is never a problem and manual cleaning is rarely required by utilizing the AutoClean functionality in which water can be jetted across the optics, effectively keeping the sensor clean.

Poor accuracy at low level turbidities

Often as a result of manufacturers setting a zero, any subsequent drift from electronics results in small errors. At low level turbidities, small errors can lead to a significant impact on the accuracy of the measurements. Due to the patent applied for optical calibration method used by the TurbSense^® this is never an issue. Any drift is removed when a new zero is established on calibration. Using this approach the end user can always have confidence in the measurements made by TurbSense^®.

To summarize, Pi’s TurbSense^® has all the functionality required to provide a highly accurate and reliable system. The instrument is free from the issues so many of the current online turbidity instruments are plagued by, and with full functionality the instrument remains competitive on price.

For a technical discussion on the effect of bubbles or on the measurement techniques employed by the TurbSense^®, click here.