The continuous monitoring NTU system shall include the online model with power supply, display, user interface and sensor as one single SKU. It will not be necessary to purchase a separate module for display or power supply. The turbidimeter shall meet all requirements specified by the USEPA Method 180.1 (White
Light Model), ISO 7027 (Infrared Model) and Standard Methods 2130B. The turbidimeter shall be Modbus compatible and have a 4-20 mA output. The turbidimeter shall have the same optical design as the M100+ laboratory turbidimeter.

The online turbidimeter shall have an ultrasonic auto-clean system. Accuracy shall be 2% of reading or plus or minus 0.02, whichever is greater, from 0-40 NTU, and 5% of reading or plus or minus 0.02, whichever is greater, from 40-1000 NTU. Resolution will be 0.001 NTU (user selectable).

The sensor shall utilize a rotational flow through assemby. The sensor shall utilize a rotational flow through assembly with a 30ml measuring cuvette. The specially designed flow head bubble rejection system will reduce the need for a bubble trap and provide a faster response time. The sample stream will remain under pressure, ensuring it will not be exposed to open atmosphere, which can cause precipitants in some circumstances. Precipitation of oxidized sample constituents can result in false NTU readings. The sensor shall allow grab samples to be measured without the need to stop sample flow to the flow head.

Calibration and standardization will be accomplished using small volumes (30ml) of reusable primary standards. Primary Standards shall be reusable for multiple online turbidimeters and also with the M100+ laboratory turbidimeter. Calibration procedures can be completed without disrupting the sample flow. Details of calibration (date and time of last successful calibration) will be stored on the analyzer. An integral part of the turbidimeter system is the inclusion of a laboratory instrument specifically designed to use the same calibration standards. The required supporting laboratory instrument must be an HF scientific M100+ touchscreen model with USB data logging and ability to store the date/time of the last calibration.

The process turbidimeter and the laboratory turbidimeter lamp source and detector shall not come in contact with the sample, eliminating false low readings. The turbidimeters shall use menu driven software. The online turbidimeter enclosure shall be ABS. The online turbidimeter will have data logging features, will store the latest date/time of calibration and be user selectable for ranges of 0 – 10 NTU, 0 – 100 NTU (factory default) or 0 – 1000 NTU. The online turbidimeter shall be HF scientific MTOL+ Online Turbidimeter.