Hach LDO, Addendum-Operation

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Figure 1 Air calibration procedure
If the value does not stabilize, the display will show "Unable to Calibrate" followed by an error
message.
Table 3 shows the error message and resolution for calibration problems.
Table 3 Air calibration error messages
Message Description Resolution
Calibration failed! Gain correction is
too high. The calculated gain value is too high. Repeat the calibration.
Calibration failed! Gain correction is
too low. The calculated gain value is too low. Repeat the calibration.
Calibration failed! Unstable The value did not stabilize in the maximum
allowed calibration time. Repeat the calibration.
Calibration by comparison
This calibration method uses an alternate sensor attached to a hand-held meter.
1. Put the alternate sensor into the process. Put the second sensor as close as possible to the first
sensor.
2. Wait for the DO value to stabilize.
3. On the controller for the first sensor, go to MENU>SENSOR SETUP>[Select
Sensor]>CALIBRATION>CALIBRATION.
4. Select the option for the output signal during calibration:
Option Description
Active The instrument sends the current measured output value during the calibration procedure.
Hold The sensor output value is held at the current measured value during the calibration procedure.
Transfer A preset value is sent during calibration. Refer to the controller user manual to change the preset
value.
5. The controller will show:
• "Is the reading stable?"
• The current dissolved oxygen measurement
• The current temperature measurement
6. When the measurement is stable, push ENTER. The display will show an entry screen.
Note: The measurement will usually stabilize in 2 to 3 minutes.
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