Hach-Lange ORBISPHERE 3650 - Manual (Page 46)

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Calibrations
6.4.3 Calibration in air (oxygen sensors only)
The oxygen sensor can be accurately calibrated in air. To perform this type of calibration, the
instrument must be set for calibration In air.
In order to calibrate the sensor in air, you will need to extract it from its mounting or flow
chamber, and wipe dry the sensor protection grille (if applicable).
Calibration is best achieved using the storage cap that protected the sensor during shipment.
Put several drops of tap water in the cap, shake out the excess, and then attach it to the sensor
by means of its collar. It is best to leave the cap slightly loose, to avoid compressing the air
inside. The cap and sensor should be about the same temperature.
Switch on the instrument, if necessary, and wait a minute or so for the displayed measurement
to settle.
1. Press the CAL button. Remember, this button may have been
locked out to prevent an accidental reset (see Locking out the
instrument’s CAL button on page 39 for details).
2. A brief clearing [---] message appears.
3. Press CAL again within a 3 second period.
4. The percentage of the measured current to the ideal one is
displayed.
5. When the reading is stable, press CAL again.
If the new calibration current is within 25% to 175% of the ideal
current, the instrument displays CAL and returns to the
measurement mode. Calibration is now complete, the sensor is
calibrated, and you can proceed with your measurements.
If the new calibration current is not within this range, the instrument
displays Err and returns to measurement mode. The system will
not calibrate, and it is likely that a sensor service will be required.