12
OPERATING DESCRIPTION
Referring to the drawing on page 7 and the Fluidic Dia-
gram on page 13, the Sample Line is connected to the
instrument at the Sample Port (#16); an internal Regulator
(#17) reduces the inlet pressure from a maximum of 4 bar
(57.2 psig) down to 1 bar (14.3 psig); from the Regulator
a nylon tube is connected to the input of the Electrovalve
(#18). The output of the valve goes to the Drain Port (#11
in PCA 300 and PCA 301 only) and then to the Measur-
ing Cell (#8). An optional Filter can be installed to the sample
port if the stream is excessively turbid.
The sample coming from the line normally flows through the
Measuring Cell. It goes out from the Measuring Cell through
the Drain Tube (#10) and the Output Port (#9).
The Measuring Cell is accessible from the port placed on the
top (#7) for speedy cleaning and maintenance.
During the time between two successive sampling, the ana-
lyzer solenoid input valve is open to allow sample flow to
flush the colorimeter cell. Every 3 to 102 minutes (user se-
lectable), the valve closes stopping the sample flow and
leaving the sample cell full of fresh sample. Cell volume is
controlled by an overflow gateway.
As the sample inlet valve closes, a series of measurements
(with LED on and off) of the unreacted sample is taken to
determine an average Blank level prior to reagent addi-
tion. The measurement of sample blank signal permits
compensation for any turbidity or natural color, and pro-
vides the zero reference point for the measurement.
The two channel Peristaltic Pump (#6) starts rotating caus-
ing a precise quantity of buffer and indicator (#14 and
#15) to enter the colorimeter sample cell where a mag-
netically coupled stirrer mixes the reagents with the sample.
After a delay for the development of color, a series of mea-
surements (with LED on and off) are taken (Sample level)
to determine an average Chlorine concentration measure-
ment. The reacted sample signal is then measured and
displayed.
This sequence is repeated every 3 to 102 minutes (user-se-
lectable).
