Dual channel on-line turbidity measurement

Emerson Process Management introduces a new turbidity measurement system, further extending the Rosemount Analytical instrumentation capability for water quality monitoring

The Clarity II turbidimeter is a dual channel on-line device complete with a unique sensor chamber that helps eliminate the erroneous readings caused by bubbles, and provides a suitable sample flow.

Operating over a wide measurement range, the Rosemount Analytical Clarity II is used to measure low level turbidity in drinking water treatment systems, and also for monitoring the higher turbidity levels normally associated with wastewater discharges, clarifier control and condensate return applications.

The Clarity II sensor is designed to conform to the turbidity measurement requirements specified in ISO 7027, using a long life LED source operating in the near infrared region, and monitoring the light scattered at 90 degrees by particles suspended in the liquid.

This technique is preferred for low-level turbidity measurements, as it is less sensitive to the effects of coloured samples.

An alternative sensor is available that conforms to the US EPA180.1 standard.

The sensor may be positioned up to 15 metres from the analyser display unit, and an interconnecting cable complete with IP65 plugs is supplied.

Options available include a three-relay alarm output, and a secondary "dry" standard to carry out routine analyser calibration checks: this minimises the cost and handling problems associated with traditional liquid standards.

The Clarity II Turbidimeter measures turbidity with an accuracy of +/-1% of reading, or +/-0.015 NTU for measurements below 1NTU, and measures up to maximum of 200NTU.

The dual channel design enables one or two sensor channels to be monitored simultaneously with independent ranges and analogue outputs.

The user configuration menus are displayed in easy-to-read full text in one of six user-selectable European languages on a two-line back-lit LCD.

Rosemount Analytical products for monitoring water and wastewater include sensors and transmitter systems for conductivity, ph, dissolved oxygen, chlorine and ozone - and now turbidity.

Further specific measurement systems have been developed for potable water chlorine measurement, where a second sensor is used to automatically correct the chlorine measurement for the interfering effects of pH variations in the sample.

This design eliminates the cost and handling problems associated with liquid or gas reagents used to continuously dose the sample in order to neutralise the interfering pH variations.

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