Hach-Lange CL17 USER MANUAL - Manual (Page 38)

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Operation
5.3 Calibration
The CL17 Chlorine Analyzer is factory calibrated. A built-in electronic curve is
preprogrammed into the instrument. This instrument does not require recalibration
unless specified by your regulatory agency for compliance reporting purposes.
If you are required to do a two-point calibration or if your sample stream chlorine
concentration is typically less than 0.5 mg/L, follow the instructions in
section 5.3.1 . If
your sample stream chlorine concentration is typically greater than 0.5 mg/L, you can
perform a Calibration by Comparison as detailed in
section 5.3.2 .
If the calibration you perform requires you to adjust the CAL ZERO by more than 0.2
mg/L, a SYSTEM WARNING caused by a MARGINAL ZERO error will appear. Similarly,
adjusting the CAL STD by more than 10% (up or down) will produce a MARGINAL GAIN
ERROR.
If either of these errors occur, reset the instrument to the default calibration (refer to
section 5.2 ), check the standards, and repeat the calibration. If the error messages
persist, contact the Customer Service department.
5.3.1 Calibration on known standards
CAUTION
Chemical exposure hazard. To familiarize yourself with handling precautions,
dangers and emergency procedures, always review the Material Safety Data Sheets
prior to handling containers, reservoirs, and delivery systems that contain
chemical reagents and standards. Protective eye wear is always recommended
when contact with chemicals is possible.
This procedure provides the best over all accuracy by establishing the zero mg/L
reference and the span setting. Perform the calibration as follows:
1. Prepare a zero chlorine reference solution by adding approximately 4 mL of Ferrous
Ammonium Sulfate, Cat. No. 181133NC, to approximately 2 liters of the normal
sample or chlorine-free demineralized water.
Note: Enter the zero value before the chlorine standard value.
2. Place a container of zero reference water above the analyzer with at least two feet of
head. Plumb the system to enable the sample flow to be shut off so the zero
reference water can enter the analyzer in its place. Allow the analyzer to run on zero
reference water for approximately 10 minutes.
3. When the readings are stable, set the zero reference.
a. Enter the SETUP menu.
b. Press the DOWN ARROW key until CAL ZERO is displayed.
c. Press ENTER to display the current measured value.
d. Press ENTER to force the value to zero.
4. Prepare a chlorine standard solution with a value between 3 and 5 mg/L. Determine
the value of the standard to the nearest 0.01 mg/L.
5. Remove the container of zero reference water and substitute the chlorine standard
solution. Allow the analyzer to run on the standard solution for approximately 10
minutes.
6. When the readings are stable, enter the SETUP menu.
7. Press ENTER when CAL STD is displayed. The current measured value is displayed.