Eagle Microsystems RA1000 - Manual (Page 4)

4
Ambient Temperature 35 degrees to 120 degrees F (2 degrees to 50
Range: degrees C)
Sample Temperature 35 degrees 120 degrees F
Range: (2 degrees to 50 degrees C)
Sample Limitations: Samples containing high concentrations of metal ions or
certain corrosion inhibitors my effect analyzer operation.
Accuracy: +/- 2% of selected range
Electronics Enclosure: NEMA 4X
Reagent Requirements:
RESIDUAL MEASUREMENT REAGENT REQUIREMENTS
Chlorine (Free) pH buffer or CO
2
gas
Chlorine (Total) pH buffer or CO
2
gas & potassium iodide
Chlorine Dioxide pH buffer & potassium iodide
Potassium Permanganate pH buffer
III. PRINCIPAL OF OPERATION
A. GENERAL
A sample of liquid is delivered to the sample filtering chamber at an
approximate rate of 500 cc/minute. The excess overflows to drain.
The sample then passes through the annular space between the two
fixed electrodes in the sensing cell. As it passes, a small direct current is
generated in direct linear proportion to the amount of chemical present in
the liquid.
The surface of both electrodes is kept clean by the continuous action of
PVC spheres agitated via a motor driven rotating striker.
This constant cleaning eliminates signal drift and recalibration providing an
accurate residual measurement. A thermistor compensates for sample
temperature variations.
The residual value is displayed on the LCD display.
B. REAGENT FEED SYSTEM
Reagents are fed into the sensing cell to lower the pH to enable reliable
measurement. The sample pH is adjusted by the buffer to a range of
4.0 to 4.5 pH. When CO
2
is used as a buffer, the pH will be lowered to
a range of 5.5 to 6.0 pH. The addition of potassium iodide, when used,
reacts to liberate free iodine and provides a means of measurement of
total chlorine residual. Refer to CO
2
BUFFERING on page 9 for CO
2
operation.