Turbidity Meter: Understanding the Basics of How It Works
Turbidity is the measure of the relative clarity of a liquid. It is an essential parameter for various applications, including water treatment, wastewater treatment, and industrial applications that involve the use of liquids. A turbidity meter, also known as a turbidimeter or nephelometer, is a device that measures the turbidity of liquids. This article aims to provide a comprehensive understanding of how a turbidity meter works.
Understanding Turbidity
Before delving into the specifics of the working principle of a turbidity meter, it is essential to understand turbidity itself. Turbidity is a measure of the amount of light that is scattered or absorbed by suspended particles in a liquid. It is generally measured in nephelometric turbidity units (NTU).
Turbidity can have a significant impact on various processes. For example, in the water treatment industry, high turbidity levels can decrease the efficiency of disinfection processes or increase the risk of bacterial growth. Turbidity can also have a detrimental effect on aquatic life and visibility in natural water bodies.
How a Turbidity Meter Works
A turbidity meter works by shining a light through a sample of the liquid being measured, and then measuring the amount of light that is scattered by the suspended particles. The amount of light scattered is directly proportional to the turbidity of the liquid.
The light source in a turbidity meter is typically a tungsten filament lamp or a light-emitting diode (LED). The scattered light is detected by a photocell or photodiode. The amount of scattered light is then converted into a reading, usually in NTU, on a display screen.
The working principle of turbidity meters can be broadly classified into two categories: nephelometric and turbidimetric.
Nephelometric Turbidity Meters
A nephelometric turbidity meter works by measuring the scattered light at an angle of 90 degrees from the incident beam. This measurement is known as the backscatter reading.
The advantage of a backscatter reading is that it is relatively insensitive to changes in the color of the liquid being measured. This makes nephelometric turbidity meters particularly useful for measuring turbidity in water treatment applications.
Turbidimetric Turbidity Meters
Turbidimetric turbidity meters measure the amount of light that is absorbed by suspended particles in a liquid. This measurement is known as the attenuance reading.
The advantage of an attenuance reading is that it can be more accurate than a backscatter reading for liquids with low turbidity. However, it is more sensitive to changes in the color of the liquid being measured.
Calibrating a Turbidity Meter
Calibrating a turbidity meter is essential to ensure accurate and reliable readings. There are various methods for calibrating a turbidity meter, including using a standard solution, a formazin solution, or a turbidity standard.
A standard solution is a solution with a known turbidity value. It is typically made by suspending a specific amount of polystyrene beads in distilled water. The turbidity of the standard solution is then measured using a reference method, such as a nephelometer.
A formazin solution is a more precise and consistent way of calibrating a turbidity meter. It is a standardized solution of 4000 NTU that is commonly used in the water industry for calibrating turbidity meters.
Finally, a turbidity standard is a certified reference material used to assess the accuracy and precision of turbidity meters. Turbidity standards are commercially available in various values and are ideal for ensuring the ongoing accuracy of turbidity meters.
Conclusion
Turbidity meters are essential instruments that are used in various applications globally. By measuring the amount of light scattered by particles in a liquid, they help ensure that liquids are safe for use and fit for purpose. Understanding how a turbidity meter works is essential to enable appropriate calibration and ensure accurate measurements.
In summary, turbidity meters work by shining light through a liquid sample and measuring the amount of light scattered by particles in the sample. They can be classified as either nephelometric or turbidimetric, and calibrating them is an essential process to ensure accurate results.
