Hach Ultra ORBISPHERE 510, Руководство оператора

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Orbisphere 510/511/512 Analyzers - Calibration Menu 59 of 138
Operator Manual
ORBISPHERE
5.2.2 O
2
Sensor Calibration
The
O
2
sensor needs to be calibrated after each sensor service. Wait for 30 minutes after
mounting a new membrane before recalibrating. 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.
O
2
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 ( See “Modify Calibration Parameters” on
page 58 ), and press calibrate.
O
2
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 ( See “Modify Calibration Parameters” on
page 58 ), and press calibrate.
The value “% last calibration” shows the ratio between the
current measurement and the previous sensor calibration.
.
The value “% variation” indicates the variation during the
last 3 measurements, which is the stability of the
measurements. A variation as low as possible is needed
for a precise calibration.
The display shows the actual calibration parameters, and
the actual readings (temperature, barometer, current).
In case of a calibration failure, consider replacing the
membrane. See the EC Sensor Maintenance Manual for
details.
Verification
Similar to the calibration procedure, but for verification of
the actual calibration values. The result of the
measurements made during the verification is not stored
and the actual calibration data is not modified.