# Multi-Wavelength Calibration of a Low-Cost High-Range Turbidimeter: Analysis of the Dispersion Regime

## TL;DR

This paper introduces a low-cost, multi-wavelength turbidimeter for measuring turbidity over a wide range, which could improve water quality monitoring.

## Contribution

A novel low-cost multi-wavelength turbidimeter is developed with calibration zones for high-range turbidity measurements.

## Key findings

- The turbidimeter can measure turbidity from 0.5 to 4000 NTU using visible and near-infrared wavelengths.
- Calibration zones were identified using formazin standards and spectral analysis.
- The method shows potential for broad environmental and industrial turbidity monitoring.

## Abstract

Turbidimetry, a method for assessing fluid clarity by
quantifying
suspended particle levels, plays an important role in various fields,
including environmental surveillance, sediment measurements, water
quality management, and diverse industrial sectors. Various optical
instruments are commercially available, normally called turbidimeter.
However, no generic calibration that can be used to convert the turbidimeter
output to NTU is possible. This work presents the development of a
low-cost multiwavelength turbidimeter designed for high-range turbidity
measurements (0.5–4000 NTU) in visible and near-infrared spectra
(500–1000 nm). Using formazin solution as a turbidimetric standard
and introducing the calibration factor concept, we
were able to determine the identification of multiple calibration
zones of the developed sensor. For calibration experiments, a portable
spectrometer was used to measure the transmitted light, thereby obtaining
a spectrum associated with each standard. Then, analysis of the obtained
spectra was performed, enabling characterization of the calibration
method employed in the study. Considering various wavelengths in the
analysis, the results suggest that the present methodology has the
potential to develop environmental monitoring practices and water
quality control. More specifically, turbidity measurements can be
performed in a wide range of NTU and wavelength values, suggesting
the feasibility of conducting analyses over an extensive turbidity
spectrum.