Hach-Lange 5740 sc - Manual (Page 18)

14
Operation
4.7 Calibration
The dissolved oxygen sensor has been calibrated at the factory to the specifications listed
on
Specifications on page 3 . Due to the inherent accuracy and stability of the luminescent
dissolved oxygen technology, sensor calibration is seldom or never necessary. The
calibration procedures will result in an instrument offset or gain correction and may be
performed if required by regulatory agencies. The air calibration is the most accurate
method. The calibration by comparison method is the least accurate and is therefore not
recommended.
For continued accuracy and repeatability, the manufacturer recommends replacing the
sensor cap after one year of operation.
4.7.1 Calibration in Air
1. Remove the sensor from the process stream and wipe with a wet cloth to remove
debris and biological growth.
2. Place the sensor in the supplied Calibration Bag, add a small amount of water
(25–50 mL) and secure the bag to the sensor body.
3. Lay the bagged probe on a flat surface where it will not be exposed to a heat source.
4. Select the Main Menu.
5. From the Main Menu, select SENSOR SETUP and confirm.
6. Select the appropriate sensor if more than one is attached and confirm.
7. Select CALIBRATE and confirm.
8. Select AIR CAL.
9. Select the available Output Mode (Active, Hold, or Transfer) and confirm.
10. “MOVE THE SENSOR TO AIR” will be displayed if the sensor is moved to air (in the
calibration bag).
11. The Air Calibration procedure will begin and “WAIT TO STABILIZE” will be displayed.
The current DO and temperature readings will be displayed. Confirm to continue.
12. The calibration will automatically occur when the reading stabilizes or when
Confirmation is selected to base the calibration on the currently displayed value. Two
to three minutes for the reading to stabilize is typical, however, if it has not stabilized
after 45 minutes, the display will ready “UNABLE TO CALIBRATE”. After calibration,
one of the responses in
Table 2 Calibration Response on page 17 will be displayed.
13. Follow the prompts to return the sensor to the process.