Hach-Lange ORBISPHERE 510_51x Basic User Manual - Manual (Page 20)

• The display shows the actual calibration parameters, and the actual readings (temperature,
barometer, current).
O
2
sensor calibration
The O
2
sensor needs to be calibrated after each sensor service. Wait at least 30 minutes after
mounting a new membrane before re-calibrating. The sensor is in contact with either:
• Air at atmospheric pressure (In Air)
• O
2
at known concentration (Direct value). The gas can be dissolved or not.
In air calibration
This calibration procedure places the O
2
sensor in water-saturated air, to provide a known oxygen
reference against which to calibrate.
Dry the sensor thoroughly, before placing the sensor storage cap under tap water. Shake off any
excess water, but leave a few drops inside the cap. Verify that the screw-on protection cap is in place
on the sensor head. If you use a Dacron mesh inside the protection cap, make sure it is dry before
attempting to calibrate. Then, loosely place the storage cap back on the sensor, holding it in place
with a few turns of its collar.
Set the calibration parameters accordingly and press calibrate.
Direct calibration
This procedure calibrates the oxygen sensor against a liquid sample containing a known level of
dissolved O
2
flowing through the sample line.
The instrument displays the sensitivity of the sensor as a percentage of the sensitivity determined
when calibration was last performed.
Set the calibration parameters accordingly and press calibrate.
O
3
sensor calibration
The sensor is either in contact with:
• Air at atmospheric pressure (In Air)
• O
3
at known concentration (Direct Value). The gas can be dissolved or not.
The procedure is the same as for the O
2
sensor. In the case of the "In air" calibration, the sensor
measures O
2
during calibration. The O
3
coefficient is deduced taking into account how the sensor
behaves in O
2
. As a different voltage is used at the anode to measure O
2
and O
3
, the O
3
measurement takes a long time to stabilize. To facilitate the follow up after an "O
3
in air" calibration,
negative values can be displayed.
H
2
sensor calibration
W A R N I N G
Potential Fire and Explosion Hazard. Handle H
2
gas with great care!
The recommended method is at known concentration (Direct Value). The gas can be pure H
2
or a
mixture of H
2
with an inert gas (e.g. a mixture of H
2
/N
2
). The known concentration is entered by the
user in the calibration parameter window. The sensor is in contact with the calibration gas (Direct
Value) in gas phase at atmospheric pressure.
N O T I C E
Make sure the H
2
concentration used for calibration is within the acceptable range for the membrane. Hach Lange
recommends the following calibration gas/inert gas combinations for calibrating with the following membranes.
See the Sensor Maintenance Manual for further details on membrane specifications:
Membrane Recommended calibration gas
2956A 1% H
2
/ 99% N
2
2952A 10% H
2
/ 90% N
2
20 English