Hach-Lange SURFACE SCATTER 7 sc Turbidimeter - Manual (Page 35)

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Operation
7. Confirm to calibrate. When the calibration is completed
successfully, the display will show GOOD CAL! and the new
calibration gain value. Confirm to accept the calibration.
8. Follow the prompt and enter the initials of the user performing
the calibration. Confirm.
9. The controller will prompt for NEW BASELINE. Confirm to
establish a new baseline or press BACK to exit.
10. Remove the calibration cylinder from the body. The instrument
is now calibrated.
11. Close the drain valve and restore the sample flow. If no
verification is done, the display will prompt to return to
measurement mode. Confirm to continue measurements.
5.5.2.2 Comparison method
The comparison method transfers the calibration of a laboratory
instrument to the on-line instrument and the practice is approved by
the EPA and Standard Methods for the Examination of Water and
Wastewater. Calibration by comparison should not be used if
sample turbidity is less than 2 NTU.
Before performing this method, make sure the laboratory
turbidimeter used is calibrated properly with primary turbidity
standards according to manufacturer directions. Sample cells for
the laboratory instrument must be free from dirt, fingerprints and
scratches. For greater convenience, the laboratory instrument
should be moved to a location close to the on-line unit(s) to be
Figure 16 Installing the calibration cylinder
1 Detector assembly 3 Light source assembly
2 Calibration cylinder 4 Turbidimeter body