Hach-Lange LDO Sensor - Manual (Page 12)

4. Let the instrument stabilize for 15 minutes before calibration. Keep the calibration bag out of
direct sunlight during stablization.
5. Make sure that the current absolute air pressure or elevation is configured correctly. Refer to
Enter the atmospheric pressure value on page 9.
Note: The manufacturer recommends the use of absolute or actual air pressure as a best practice.
6. Go to MENU>SENSOR SETUP>[Select Sensor]>CALIBRATE>AIR CAL.
7. 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.
8. The controller will show "Move the probe to bag". Allow the value to stabilize. Push ENTER to
accept the stable value. Alternately, let the calibration continue until the display shows
"Complete".
9. When the sensor is calibrated, put the sensor into the process. Push ENTER.
Figure 6 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
Cal fail, gain high The calculated gain value is too high. Repeat the calibration.
Cal fail, gain low The calculated gain value is too low. Repeat the calibration.
Cal fail, unstable The value did not stabilize in the maximum allowed calibration time. Repeat the calibration.
Sample CAL - 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]>CALIBRATE>SAMPLE CAL.
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