37
Operation
8. Press ENTER and edit the value. Press ENTER again to accept the value.The
measured value will be forced to the entered value. Press the
EXIT key three times to
return to normal display mode.
9. Remove the standard and restore sample flow to the analyzer. The instrument is now
calibrated.
5.3.2 Calibration by comparison
Note: Make sure sample chlorine concentration is relatively stable before taking a grab sample for
laboratory analysis. Perform the laboratory analysis as quickly as possible.
Calibration by comparison involves analyzing the sample stream with a reliable, accurate
laboratory method, such as a DPD spectrophotometric or amperometric titration method
then setting the analyzer to match. Accuracy specifications over the full 0 to 5 mg/L range
cannot be assured unless the sample chlorine concentration used for calibration is
greater than 3.0 mg/L. Setting the calibration at a lower concentration may provide
accuracy at that point but can cause large errors in other portions of the span.
Perform a calibration by comparison as follows:
1. When the sample chlorine concentration is relatively stable, obtain a grab sample for
analysis.
2. Perform a laboratory analysis (DPD spectophotometric or amperometric titration
method) on the grab sample and record the value.
3. Enter the
SETUP.
4. Press
ENTER when CAL STD is displayed. The current measured value is displayed.
5. Press
ENTER and edit the value to match the value from the laboratory analysis.
Press
ENTER again to accept the value. The measured value will be forced to the
entered value.
6. Press the
EXIT key three times to return to normal display mode.
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