Model C10/77 Laser Particle Counter
from Analytical Technology

Turbidity monitoring of filtered potable water provides an excellent indicator of water clarity as well as a reliable measure of general filter efficiency. Recent studies, however, indicate that particle count data can provide additional information concerning filter operation and often can provide an early warning of filter breakthrough before turbidity values begin to rise. In addition, particle count data can indicate breakthrough of particle in the Cryptosporidium (5-7 micron) or Giardia (9-11 micron) size ranges before any change in turbidity can be detected.

On line particle measurement can be an extremely valuable operating tool for any water plant striving to meet increasingly stringent surface water treatment regulations. The response of treatment processes to changes in chemical addition can be measured with high sensitivity, helping to optimize suspended solids removal. Filter backwash operations can be monitored to ensure that particle counts have declined to low levels before the filter effluent is again allowed into the distribution system. Log removals can be easily monitored on individual filters and recorded to document system operation. These and other benefits of particle monitoring can easily be incorporated into any water treatment monitoring system.

ATI's Model C10/77 Particle Sensor is designed to provide valuable particle data by continuously monitoring particle counts in raw water, filter influent or filter effluent. Based on a laser light blocking principle, this sensor will provide particle count data over size range from 2 to 400 microns, with three 4-20 mA analog outputs and an RS-232/485 digital output supplied as standard. The scaling of the three 4-20 mA outputs is selectable by use of DIP switches mounted on the counter circuit board and can be set from 0-127 up to 0-32,000 counts per mil with one channel proportional to total particles, one channel proportional to particles in the range of 3-5 microns and one channel proportional to particles in the range of 7-10 microns. The digital output provides actual particle counts for particle sizes 2, 3, 5, 7, 10, 15, 20 and 200 microns. This data can be used for computerized calculations for filter removal efficiencies as well as trending of particle data.

Each C10/77 Particle Sensor contains an integral LED display used to indicate either raw count data or differential counts. The user may select a display of the total particles above a certain size or differential counts of 2-3, 3-5, 5-7, 7-10, 10-15 or 20-200 microns. The display is operated from sealed membrane switches on the front of the unit. Particle alarm indication can also be programmed at the counter so that high particle counts are indicated locally.

Data from other devices can also be monitored through the C10/77 counter. Each unit contains 3 optically isolated 4-20 mA input channels. This allows data from other instruments such as turbidimeters, pH monitors, residual chlorine monitors, etc to be read over the RS232/485 communication link using the WaterTrak software package.

Particle sensors require relatively little in the way of operator maintenance or adjustment. Sensors are factory calibrated and do not require field adjustment. The only requirement is that sample flow be maintained at 60 cc/min. This can be done conveniently using a constant head flow control supplied as part of the sensor assembly. The flow controller also serves as a degassing chamber to remove entrained air, which can cause inaccurate particle measurements.

Software for PC based particle count data acquisition and display is available with C10/77 counters. The software consists of the LHLink communication driver and WaterTrack display software. The LHLink driver communicates with up to 12 counters and transfers information by DDE (dynamic data exchange) directly into Excel. The WaterTrack software is an Excel application that provides particle count display in tabular and graphic form and storage of accumulated data in daily filters. Direct user customizing can be done by any user familiar with Excel spreadsheet programs.

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Last Revised: 1/23/07