Hach ORBISPHERE 29122 User Manual page 13

Choose OK to continue. The calibration procedure then displays a Pressure Calibration dialog box.
The Measured Pressure value shows the current instrument pressure reading.
Enter the current atmospheric pressure, in mbars, in the Calibration Pressure entry box. Choose
Calibrate to direct the instrument to read and display the Measured Pressure using this calibration
value. Choose Quit when you are satisfied with the pressure calibration to return to normal
operation.
6.2 Calibration range checking
When calibrating the sensor in air or in a span gas, as detailed in
new calibration current should be between 25% to 175% of the ideal current (which is stored in the
instrument's non-volatile memory for each membrane). If not, the instrument displays Err on its LCD
and the system will not calibrate. When the system will not calibrate, it is likely that a sensor service
will be required.
Note: This calibration range checking can be enabled or disabled using the WinLog97 program (see
calibration range checking
measurement situations it may be necessary to disable range checking. This will allow calibration between 0% to
999% of the ideal current. Contact a Hach Lange representative before disabling this range checking feature.
6.3 Sensor calibration
When delivered, the sensor is pre-calibrated. However, it should be re-calibrated on site, when being
used for the first time, and always after a membrane change. If you have just replaced the
membrane, allow at least half an hour for the membrane to settle before attempting to calibrate.
If you want to verify the accuracy of the calibration, place the analyzer back in measurement mode
and compare your displayed gas concentration against the value in the appropriate tables found in
the accompanying Calibration Tables booklet.
Your calibration is stored internally and is valid for the life of the sensor's membrane, thus it is not
necessary to repeat the calibration procedure until after the next membrane change.
The sensor can be calibrated either by using a span gas, directly in line in a liquid sample, or in air.
The mode of calibration may be selected using the WinLog97 program or directly from the instrument
(see Selecting type of calibration
6.3.1 Calibration in span gas
The span gas calibration procedure may be used if you have a supply of gas with a known
concentration of O (in % units). To perform this type of calibration, the instrument must be set for
2
calibration In a Span Gas. The WinLog97 program also must be used in this procedure.
Switch on the instrument, if necessary, and wait a minute or so for the displayed measurement to
settle. Then expose the sensor to a span gas sample with a known oxygen concentration. Enter the
percentage of oxygen in the span gas using the WinLog97 program (see
on page 12).
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
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.
on page 12). It is recommended to leave this checking feature enabled. In special
on page 11 for more details).
Sensor calibration
Entering a span gas value
on page 12 for details).
on page 13, the
Sensor
English 13