METHOD OF ANALYSIS
Free available chlorine oxidizes the DPD
indicator reagent at a pH between 5.5 and
6.0 to form a magenta-colored compound.
The intensity of the resulting color is propor-
tional to the concentration of chlorine in the
sample. The purpose of the buffer solution
is to maintain the proper pH.
To measure total residual chlorine (free
available chlorine plus combined chlorine)
the PCA adds potassium iodide. The chlo-
ramines in the sample cause iodide ions
to become iodine which then act with free
chlorine to oxidize the DPD indicator. After
the chemical reaction is complete, the optical
signal at 555 nm is compared to the signal
measured through the sample (before the
reagents were added). From these measure-
ments chlorine concentration is calculated.
pH AND TEMPERATURE MEASUREMENT
The HI1005 pH/temperature probe provides at the out port a potential proportional with the pH. The
temperature is measured with Pt100 platinum sensor.
For increased accuracy the pH is corrected with temperature and with the calibration coefficients. Up
to 2 buffers can be used for calibration.
The temperature can be displayed in °C or °F.
The probe can withstand pressure up to 6 bar (87 psi).
ORP MEASUREMENT
The HI2008 probe provides at the out port a potential proportional with the ORP value. The value is
directly displayed in mV. The probe can withstand pressure up to 6 bar (87 psi).
After a delay for the color development, a series of measurements (with LED on and off) are taken
(sample level) to determine an average chlorine concentration measurement. The reacted sample
signal is then measured and displayed.
This sequence is repeated every 3 to 90 minutes (user-selectable).
OPERATING DESCRIPTION
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