With the VisoTurb® 700 IQ and ViSolid® 700 IQ sensors, WTW presents a family of optical sensors for turbidity and suspended solids measurement. These sensors incorporate a ultrasound cleaning system that guarantees low maintenance and long-term reliability of the sensors. Turbidity measurements in aqueous media with VisoTurb® are carried out nephelometrically in compliance with EN ISO 7027. Solid matter measurement with ViSolid® is performed according to the principle of scattered light measurement.
Turbidity Measurement according to the Nephelometric Principle:
Using this principle, scattered light is measured at an angle of 90 degree. This method is ideal for low and medium range turbidity up to 4000 FNU. In compliance with EN 27027 and ISO 7027, infra red light with a wavelenght of 860 nm is used. This wavelength is outside of the visible range – thus potential coloration of the sample does not effect the measurements.
|FNU; NTU; TEF||0.05 ... 4000 FNU|
|mg/l SiO2; ppm SiO2||0.1 ... 4000 mg/l SiO2|
|g/l TSS||0.0001 ... 400 g/l TSS|
Measuring Principle of Suspended Solids:
With increasing concentration of suspended solids, particles will interfere with each other. With this increasing number, not every particle is reached by the light source or the reflected light is not detected by the receiving device – thus incorrect values are measured. So the 90 degree scattered light method used for the turbidity measurement can only be used for lower concentrations.
For this reason WTW uses two methods of measurement – depending on the concentration. For lower concentrations, a scattered light method is used, in case of higher concentrations, the backscatter method is the better choice.
|g/l SiO2 / % SiO2||0.01 ... 300 g/l SiO2
0.001 ... 30% SiO2
|g/l TS / % TSS||0.003 ... 1000 g/l TSS
0.0003 ... 100% TSS