General concept of turbidimeters

Turbidimeters are devices designed to measure the turbidity of a liquid, usually water, which is the measure of opacity or the amount of suspended particles that scatter light. This measurement is essential to evaluate water quality in different industrial, environmental and water treatment processes.

Turbidity is expressed in nephelometric turbidity units (UNT) or nephelometric turbidity units (NTU), which quantify the amount of light scattered at a specific angle. Turbidimeters use optical principles to determine this dispersion, providing a rapid and accurate measurement of the presence of suspended solids.

Light scattering and optical measurement

The basic principle of a turbidimeter is based on light scattering. When a beam of light falls on a liquid sample containing suspended particles, part of that light is scattered in different directions. The intensity of this scattered light is proportional to the concentration and size of the particles present.

Turbidimeters typically measure scattered light at a 90-degree angle to the incident beam, as this angle provides a more linear correlation with the concentration of suspended particles. This technique is called the nephelometric method, which is the standard for measuring turbidity.

In addition to scattered light, some instruments can also measure light transmitted through the sample to determine turbidity, although this method, known as the attenuation method or turbidimetry, is less sensitive than nephelometric.

Optical and electronic components

A turbidimeter is mainly composed of a light source, a photodetector to capture the scattered light, a sample compartment, and an electronic system to process the signal and display the turbidity value. Commonly used light sources include LED or tungsten lamps, which offer a stable and suitable wavelength for measurement.