The Delta Analytical Model 924 Chlorine Measurement System provides accurate, sensitive, reliable, and
troube-free operation using amperometric sensor techniques. A multiple use instrument, the 924 measures
(1) HOCL; (2) HOCL + OCL (TFC/total free chlorine) manually if pH is known and controlled; and (3) TFC
automatically if equipped with a pH sensor. There are no sample pumps, reagents, or dilution systems
required, making this system superior to amperometric wet chemistry analyzers.
The sensor is protected from direct contact with the stream by a chlorine-permeable membrane. When
chlorine permeates the membrane, it reacts electrochemically with the cathode and causes a linear current,
proportional to the chlorine concentration, to flow between a voltage-based gold cathode and silver anode. This
current is then processed in the microprocessor-based analyzer transmitter and displayed on the 3 1/2 LCD
The Chlorine Analyzer/Transmitter System consists of two separate units: an Analyzer/Transmitter and an
amperometric sensor. The Analyzer/Transmitter is housed in rugged NEMA 4X enclosure which is suitable for
either surface or handrail mounting. The system utilizes microprocessor based electronics to ensure stable
readings over a wide range of operating conditions.
The sensor is available with two different mounting systems to meet varying installation requirements. The
Model 921243 sensor may be mounted directly in the sample using Delta Analytical's exclusive "sweep-ell"
handrail mounting system or may be mounted in a flow-thru "tee" for in-line sample measurements. The same
sensor can be used for either application.
The Model 921243-XXX Amperometric Sensor is composed of a PVC body, gas permeable membrane, a gold
cathode, a silver anode. The sensor also has a precision thermistor built into it, for temperature compensation
of Chlorine readings and for temperature readout over the range of 0
to 50° C. The sensor is provided with a
screw-on type membrane cap for easy maintenance.
THEORY OF OPERATION
The Delta Analytical Model 924 instruments are supplied with an amperometric sensor which can be located in
any part of a stream or water flow. The sensor has a gold cathode at its tip, and an internal silver anode. The
body of the sensor is filled with No. R-448 Electrolyte. Unique channels in the body bring electrolyte solution
from the reservoir to the gold cathode under a special permeable membrane. In use, water being analyzed is
made to flow past the tip of the sensor. As hypochlorous acid molecules diffuse through the membrane, an