Hach-Lange 1720E Low Range Turbidimeter - Manual (Page 26)

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Operation
4. Select PERFORM TEST and confirm. Select the available Output Mode (Active, Hold,
or Transfer) from the list box and confirm.
5. Select WET for the verification type and confirm.
6. Enter the Std Turbidity and confirm.
7. Drain and clean the sensor body and confirm.
8. Pour the standard into cylinder. Replace the head and confirm.
9. The reading will be displayed. Confirm to accept the verification.
10. Return the sensor to measure mode and confirm.
5.6 Calibration and Verification History
The calibration and verification history logs contain information on the last 12 calibrations
and the last 12 verifications. The calibration history log shows the gain value, the time and
date of the calibration, and the initials of the operator performing verification.
Note: Restoring default settings from the DIAG/TEST menu will return the turbidimeter to its non
calibration state (gain = 1.0) but it will not remove the previous calibration history from memory.
The calibration history log is accessed from the Calibrate menu. The verification history
log is accessed from the Verification menu (a submenu of the Calibrate menu).
Each verification history entry shows the serial number of the verification device (dry
verification) or the value of the verification standard (wet verification), the time and date of
the verification, and the initials of the operator performing the verification.
Scroll through the entries by pressing the ENTER key. After scrolling through all 12
histories, the display will return to the calibration menu level.
When the instrument is received from the factory, default values or blank spaces will be
shown for the calibration and verification history information. Those values will be replaced
with real data as the history log is filled.
The data is retained as first in, first out. When the log is full, the newest entry is stored and
the oldest entry in the log is deleted.
5.7 Offset Feature
The offset or clean water offset (CWO) feature will allow a ± 0.05 NTU offset to the
measured value. The offset value denoted as CWO will be subtracted from the value
displayed on the sc Interface. The 0.05 NTU offset can be entered after a calibration is
complete and is based on an independent determination of the water used in the
preparation of the turbidity standards.
Note: The offset is a limited value. An offset outside the range of ± 0.05 mg/L, ± 0.05 NTU,
± 0.05 TE/F, ± 0.05 FTU or ± 0.05 Degree will not be accepted.
For example, if a standard is prepared with a value of 0.8 NTU, the 0.05 NTU offset would
result in a displayed value of 0.75 NTU. See the
Setting the Offset section to change the
offset value. When the offset is used, the letters CWO are displayed after the turbidity
value in the upper-right corner.