Portable Nephelometric Turbidity Meter

What is the Portable Nephelometric Turbidity Meter?

A portable nephelometric turbidity meter measures 90-degree light scatter in a battery-powered handheld or field case format. It brings compliant turbidity readings directly to rivers, wells, treatment works and remote sampling points.

Overview

The instrument holds a sample vial in a fixed optical well with a light source and a 90-degree detector matched to ISO 7027 or EPA 180.1. A microprocessor converts the detector signal into NTU using stored calibration from formazin or polymer standards, and readings stabilise within seconds to a minute. Typical ranges span 0 to 1000 NTU with resolution of 0.01 NTU below 10 NTU, and accuracy of about ±2 percent of reading plus 0.01 NTU at low levels. Rugged housings, backlit displays and water-resistant seals suit field use, and many models log readings with time and sample identification. Calibration is usually done with sealed standard vials in the field and checked against formazin in the laboratory.

How does it work?

Nephelometric turbidity measurement shines a light beam into the sample and measures the light scattered at 90 degrees by suspended particles, since scattering increases with particle number, size and refractive index. ISO 7027 specifies the optical design, including wavelength and detector geometry, while EPA 180.1 specifies a tungsten lamp and a slightly different geometry, so instruments are usually labelled to one method. Ratio turbidimeters add a second or third detector at other angles and divide the signals, which compensates for colour and lamp ageing and extends the useful range. Backscatter instruments measure light scattered at angles greater than 90 degrees and suit high-turbidity samples beyond the range of nephelometry. Turbidity is formally a ratio of scattered to transmitted light and is reported in nephelometric turbidity units (NTU).

What are the key features?

• 90-degree nephelometric optics matched to ISO 7027 or EPA 180.1
• Range 0–1000 NTU with 0.01 NTU resolution at low levels
• Water-resistant housing and backlit display for field use
• Sealed primary standard vials for field calibration
• Data logging with time and sample ID
• Battery operation for a full working day

What are the technical specifications?

A typical portable nephelometric turbidity meter configuration offers method compliance of ISO 7027 or EPA 180.1, model specific, range of 0–1000 NTU, resolution of 0.01 NTU below 10 NTU, 1 NTU above, accuracy of ±2 percent of reading plus 0.01 NTU, light source of LED, 860 nm or tungsten and detector of Silicon photodiode at 90 degrees. Values are indicative of the product class; the exact figures for each configuration are confirmed on the quotation and the calibration documents supplied with the instrument.

Which applications is it used for?

The Portable Nephelometric Turbidity Meter is used in field verification of drinking water turbidity, river, lake and well sampling surveys, wastewater plant sampling rounds and emergency and remote site water checks. Across the wider Turbidity Meters class, laboratories also deploy it for drinking water turbidity compliance testing, filter performance and backwash control and raw water and river quality monitoring.

Which standards and certifications apply?

Relevant standards and methods include ISO 7027-1, ISO 7027-2, EPA 180.1, Standard Methods 2130 B and ISO/IEC 17025. Certification candidates for this model are CE, ISO 9001 manufacturing and ISO 7027 design compliance; each is to be confirmed for the specific configuration before shipment, and certificates are supplied only where they have been issued.

Turbidity is sensitive to handling, so sample bottles should be clean and free of scratches, and measurements should be made promptly because particles settle and temperature changes. Dilution changes the particle population and is generally avoided. Formazin is the primary standard but is toxic and unstable, so stabilised formazin or polymer standards are used routinely and replaced before expiry. Low-level instruments need careful zeroing with ultrapure water and checks for stray light and bubbles, which cause positive bias. Online instruments require scheduled cleaning of the optical windows and verification against grab samples. Keep calibration records, and note the method and instrument model on every report, since results from different optical designs are not directly comparable.

How do I select the right Portable Nephelometric Turbidity Meter?

Choose a portable meter when turbidity is measured at multiple field locations and readings are needed quickly. Confirm that the optical design matches the method your regulation names, and check whether field calibration standards and low-range resolution suit your measurement levels.

How does it compare with other Turbidity Meters variants?

Start from the method named in your regulation, because ISO 7027 and EPA 180.1 instruments are not interchangeable for compliance reporting. Portable meters suit field checks, river surveys and emergency sampling, while benchtop instruments give better repeatability and temperature control for laboratory compliance work. Ratio turbidimeters handle coloured or strongly absorbing samples better and reduce the effect of lamp drift. Choose a backscatter instrument when samples exceed the nephelometric range, as in sludge and raw wastewater. Online analyzers provide continuous data for filtration and coagulation control and are typically calibrated against the laboratory meter. Confirm the calibration standards, the range required and whether low-level resolution near 0.02 NTU is needed.