How is turbidity measured?

Document ID

Document ID TE403

Published Date

Published Date 10/18/2018
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Question
How is turbidity measured?
Summary
Turbidity measurement
Answer
Turbidity is measured using instruments called turbidimeters. Traditional turbidimeters shine light through a section of water and detect how much light is scattered from particulates in the water at a 90-degree angle from the incoming light. This type of scattered light measurement is called nephelometric. These turbidimeters are designed for field or laboratory measurements as well as for round-the-clock monitoring, where an alarm can be set to go off when turbidity levels reach unsafe levels.

The latest technology for measuring turbidity uses a laser to measure light scatter at 90 degrees, 360 degrees around the sample.  This new technology offers unparalleled optical precision, faster results and greater confidence in your online and benchtop measurements.  The TU5 technology is also EPA approved.  Its everything about turbidity, faster, better, and easier.

Turbidity can also be approximated in an instrument such as a colorimeter or spectrophotometer by measuring the decrease in transmitted light due to blockage by particles. This type of measurement, however, is not considered valid by regulatory agencies and does not fit the definition of turbidity by the American Public Health Association. Transmittance measurements are also susceptible to interferences such as light absorption from color or particle absorption. Additionally, there is no correlation that can be made between transmittance versus nephelometric measurements. Nevertheless, colorimeters and spectrophotometers are sometimes used for determining large changes in the turbidity of a water system or for process control.

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