... typically
communicated every minute.
The comparator provides a simple way to convert the particle size information
from an analog pulse to a digital count value. It is a very basic form of analog -to-
digital ... involves analog -to- digital (A/ D) conversion.
1. Voltage Comparator
A comparator is simply a small circuit that “compares” an input signal to a fixed
referen...
... at a time. If a spare
is available it can be rotated into service. The maintenance log should be kept up-
to- date, and calibration stickers displaying the date of calibration placed on each
particle ... practical.
2. Particle Counter Calibration Verification
Verifying calibration is an easier and more practical step for the water plant
operator. Only a couple of partic...
... voltage range of a chart recorder or SCADA analog
input is 1 to 5 V. A 250
Ω
resistor is required to convert a 4 to 20 mA signal into a
1 to 5 V signal.
Another benefit of the 4 to 20 mA current ... some cases, flow alarms can be signaled by the particle
counter via the computer data collection system.
A. DIAGNOSTIC SIGNALS, ALARMS, AND DISPLAYS
The most common alar...
... into usable form. Many laypeople are confused by the distinction
between the industry standard signal formats (RS- 485 and RS-232) and the non-
standard protocols. To make an analogy, the signal ... the name implies, a constant “exchange” of
data between the particle counter software package and a SCADA software package.
The particle counter data are output to a temporary locati...
... constant, high-quality, and rea-
sonably affordable standard for size calibration of particle counters.
C. PARTICLE SIZE CALIBRATION
To calibrate a particle counter for sizing accuracy, standards covering ... wider
acceptance in the drinking water treatment industry. The desire for standards for
both instrument accuracy and cross-comparison of data has placed an increa...
...
160 A PRACTICAL GUIDE TO PARTICLE COUNTING
It is an advantage to be able to clean the flow cell without opening the NEMA
enclosure, since water may be spilled into the enclosure. Chemtrac and ARTI ...
E. ANALOG OUTPUTS
Met One offers separate particle counter models for serial data and 4 to 20 mA
output. The serial data model can provide 4 to 20 mA output data as...
... most of the standard SCADA optomux
drivers are incomplete and must be modified to accommodate it. Any of the manu-
facturers may have developed an interface for a particular SCADA package, so it
never ... require a little more effort
to clean and maintain, and a particular style of software presentation may be more
suited to a given set of operators. Although it is becoming les...
... Packaged Treatment Plants
Packaged treatment plants, as touched on above, are prefabricated plants, which
are more cost-effective than ground-up plants for smaller applications. A packaged
plant ...
16 A PRACTICAL GUIDE TO PARTICLE COUNTING
At the most basic level, particle counters could not be a more natural fit for
drinking water treatment. After all, water...
... PRACTICAL GUIDE TO PARTICLE COUNTING
The disadvantage to this approach is that the particle counter data are collected
and displayed separately from the other plant data, requiring separate training ... second alternative is the direct interface of the particle counters to SCADA
using serial data communications. All count data, as well as status and alarm
information, are t...