ATI’s Model A15/76 Turbidity Monitor is designed to meet the needs of both municipal drinking water systems and industrial water treatment for reliable, low-range turbidity measurement. The turbidity sensor is available with either a White Light Source for EPA Method 180.1 compliance monitoring, or an infrared light source for non-reporting applications.

Using a 90 degree scatter measurement, the system provides high sensitivity measurement with unmatched zero stability.  Turbidity measurements down to 0.001 NTU or as high as 4000 NTU can be measured with the same monitor, eliminating the need for separate high and low range instruments.

The turbidity sensor used in the A15/76 monitor is a planer sensor with the light source and photo detector mounted on a flat face. Lenses in front of the light source direct the beam of light at a 45-degree angle into the sample.  Another lens in front of the photodetector collects the 90 degree scattered light and directs it to the detector. The signal generated by the detector is amplified inside the sensor for transmission to the display unit. Periodic pulsing of the light source allows the sensor zero to be adjusted automatically for improved stability in low-range applications.

Turbidity sensors are available for measurement in a pressurized flowcell or for direct submersion in open tanks. A 1-1/2” flow T assembly is also available for direct in-line measurements. The flowcell is required for very low measurements (0-4 NTU), while the submersion unit may be used for higher turbidity applications such as wastewater effluent or raw water.

Air bubbles are a common problem in many turbidimeters.  ATI’s turbidity sensor is designed to operate under pressure to eliminate the sample degassing that often causes air bubble errors. Sample pressure is not dropped until the sample exits the measuring chamber, resulting in more reliable measurements. The turbidity electronics unit is a compact panel-mount instrument providing an LCD display of turbidity value, as well as indication of alarm status and instrument diagnostics. For stand-alone applications, a NEMA 4X wall-mount enclosure is available.

______ (Quantity) Turbidity Monitors shall be supplied for continuous monitoring of turbidity in ___________ (Specify Application and Location). The turbidity monitoring system shall consist of an electronic monitor, sensor and accessories listed below. The Turbidity Monitoring System shall be ATI Series A15/76 as described below.

Turbidity Monitor

The Turbidity Monitor shall be a compact ¼ DIN size instrument suitable for panel mounting. For outdoor applications, the monitor shall be supplied in a NEMA 4X enclosure with a clear hinged door to allow tool-less access to controls and for viewing the LCD display. The display shall be alphanumeric LCD and capable of indicating turbidity in NTU’s (Nephelometric Turbidity Units) in a range up to 4000 or selectable in mg/l to a range up to 9999. Alarm condition, setpoints and all configuration information shall be programmable through a front keypad with a software lock protecting configuration programming, with an access code.

The monitor shall provide two independently programmable alarm/control relays assignable over the entire measuring range of the instrument as either low or high alarm. In addition, both relays shall be programmable for variable deadband and variable time delay. A third independent alarm relay shall be provided having two setpoints, one for low conductivity level and one for high level. This alarm relay shall activate if either of the setpoints are exceeded.

The monitor shall provide sensor diagnostic functions to warn of conditions that cause inaccurate or invalid readings and to continuously monitor for optical fouling of the sensor, displaying an alarm message when the sensor requires cleaning.

An isolated 4-20 mA analog signal shall be provided, adjustable to any range within the display scale and suitable for loads up to 600 ohms.

Turbidity Sensor

The turbidity sensor shall employ a bright LED light source producing an infrared light beam, and located behind an optical lens focused into the process at a 45° angle with a photo receiver also focused at  45°. The light is then scattered at a 90° angle by the particles. Sensors shall be available for direct immersion, in-line flow applications or self-cleaning. Sensor shall be made of Delrin and have clear Acrylic optical windows.