Hach ORBISPHERE 3655 Manuel D'utilisation Simplifié page 15

Choose OK to continue. The calibration procedure then displays a Pressure Calibration dialog box.
The Measured Pressure value shows the current instrument pressure reading.
Note: Since the instrument is sealed against moisture, you must open the barometric pressure sensor relief valve
switch (location depicted in
equilibrium, and take an accurate barometric 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 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
6.2.1 Calibration in span gas
The span gas calibration procedure may be used if you have a supply of gas with a known
concentration in % units (use O
type of calibration, the instrument must be set for 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 gas concentration. Enter the
percentage of gas in the span gas using the WinLog97 program (see
on page 14).
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.
6.2.2 Calibration in line
The in line calibration procedure can be used to calibrate the sensor directly in line, against a liquid
sample with a known dissolved gas concentration. To perform this type of calibration, the instrument
must be set for calibration In line. Switch on the instrument, if necessary, and wait a minute or so for
the displayed measurement to settle. Expose the sensor to a liquid sample with a known gas
concentration.
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.
Figure 1 on page 5) to permit the instrument to achieve atmospheric pressure
on page 13 for more details).
for oxygen sensors or H
2
for hydrogen sensors). To perform this
2
Entering a span gas value
on page 14 for details).
on page 14 for details).
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