Turbidimeters are essential instruments used to measure water clarity by detecting the presence of suspended particles that cause cloudiness or turbidity. This measurement is a critical indicator of water quality, helping to identify pollutants, sediments, and microorganisms. Whether you're monitoring drinking water, wastewater, or natural water bodies, turbidimeters provide a reliable and efficient way to assess safety and cleanliness.

How Do Turbidimeters Work?

Turbidimeters function using either nephelometric or transmitted light methods:

  • Nephelometry involves shining a beam of light through a water sample and detecting the scattered light at a 90° angle. The intensity of scattered light increases with the number of suspended particles.

There are two primary types:

  • White-light turbidimeters (compliant with US EPA Method 180.1) measure turbidity in NTU (Nephelometric Turbidity Units) and are ideal for drinking water applications.
  • Infrared turbidimeters (compliant with ISO 7027) measure in FNU (Formazin Nephelometric Units) and are better suited for colored or murky samples, as infrared light reduces interference from water color.

Turbidity readings can be affected by:

  • Particle size and shape
  • Concentration of suspended matter
  • Sample color and light scattering behavior

Because of this, turbidity is often used as an indirect indicator of harmful microbes or contaminants in water.

The Impact of High Turbidity

Elevated turbidity levels may lead to significant water quality concerns:

  • Protects harmful bacteria from disinfectants like chlorine or UV
  • Reduces the effectiveness of water treatment
  • Blocks sunlight, disrupting aquatic ecosystems
  • Promotes sediment buildup, especially after heavy rainfall or construction activities

In the UK, drinking water turbidity is required to stay below 1.0 NTU, with most treatment facilities targeting below 0.5 NTU for optimal clarity and disinfection.

Advantages of Portable Turbidimeters

Portable turbidimeters offer convenient, on-site turbidity testing with fast and accurate results:

  • Easy to operate without the need for a lab
  • Immediate results at the point of use
  • Battery-powered and rugged for field conditions
  • Ideal for environmental monitoring, education, and water treatment operations

Top Apera Portable Turbidimeter Models

Apera Instruments is well-known for manufacturing reliable and user-friendly turbidimeters. Here are three popular portable models:

1. TN420 – White Light Turbidimeter

A compact and EPA-compliant device ideal for clear water testing.

Features:

  • White light source (EPA Method 180.1)

  • Measurement range: 0–1000 NTU

  • Automatic calibration

  • Suitable for both lab and field use

Use Case: Drinking water analysis, industrial water testing, and government monitoring.

2. TN480 – Infrared Turbidimeter

Designed for accurate testing of colored or murky samples.

Features:

  • Infrared light (ISO 7027 compliant)

  • Measurement range: 0–4000 NTU

  • High accuracy in difficult water conditions

  • Built-in data logging

Use Case: Wastewater analysis, environmental sampling, and stormwater runoff monitoring.

3. TN500 – Advanced White Light Turbidimeter

An enhanced model for professional applications requiring extended measurement capabilities.

Features:

  • EPA-compliant white light

  • High resolution with extended range

  • Dual-mode (lab and field use)

  • USB data export for easy reporting

Use Case: Research projects, long-term monitoring, and high-volume water testing.

4. TN400 – Infrared Turbidimeter

A compact and robust option for field testing of colored or murky samples.

Features:

  • Infrared light source (ISO 7027 compliant)

  • High accuracy in multicolored or low-clarity water

  • Easy operation with portable design

  • Ideal for environmental monitoring

Whether you’re ensuring drinking water safety or monitoring the environment, portable turbidimeters offer fast, dependable, and accurate turbidity readings. With models like the TN420, TN480, and TN500, Apera Instruments delivers quality solutions trusted by professionals, educators, and field researchers alike.

Invest in a turbidimeter today—and check water clarity with confidence.