Hach ORBISPHERE 3655 Manuel D'utilisation Simplifié page 14

Choose In Air to allow calibration of the sensor in air (only applicable to Oxygen sensors). Choose In
Line to calibrate the sensor directly in the sampling line, in a sample of known gas content or select
In a Span Gas to calibrate in a source of gas of known oxygen or hydrogen concentration. Choose
OK when the desired mode is selected.
5.4.3.2 Select from the instrument
1. Switch the instrument power OFF
2. Switch the instrument on by holding down the CAL button and then pressing the POWER button
while still pressing the CAL button
3. The instrument display will show either SPA for span gas calibration, LI for in line calibration, or
Air for in air calibration
4. Use the Up/Down Arrow buttons to change the mode to your choice
5. Press the STO button to set the selected mode. The instrument displays Sto for a few seconds,
then returns to measurement mode
5.4.4 Locking out the instrument's CAL button
You can use the Configuration, Calibration Key Status menu to prevent an accidental sensor re-
calibration from the instrument keyboard.
Choose Disabled to lock out the keyboard CAL button. To unlock this capability, choose Enabled.
Choose OK when the desired mode is selected.
5.4.5 Sensor calibration range checking
When calibration is performed for In Air and In a Span Gas calibration modes, the sensor
measurement current is compared to an ideal current for the selected membrane to determine
whether or not to complete the calibration. You can use the Configuration, Calibration Range
Checking menu to enable or disable sensor calibration range checking in the instrument.
Choose Disabled to calibrate without checking the value of the measurement current, within a range
of 0% to 999% of the ideal current.
When set to Enabled, at calibration the measurement current should be between 25% and 175% of
the ideal current; if the value is outside of these limits, the calibration fails and Err is displayed on the
instrument LCD. Choose OK when the desired mode is selected.
Note: It is recommended to leave range checking enabled. In special measurement situations it may be necessary
to disable range checking. However, contact a Hach Lange representative for further details before disabling this
feature.
5.4.6 Entering a span gas value
When calibrating the sensor in a span gas, use the Configuration, Span Gas menu to enter the
concentration of the gas to be measured in the span gas. Enter the percentage of measurement gas
in the span gas (e.g. 10.00%), then choose OK.
Section 6 Calibration
6.1 Pressure calibration
Since the instrument is sealed against moisture, you must open the barometric pressure sensor relief
valve switch on top of the instrument (see
instrument to achieve atmospheric pressure equilibrium, and take an accurate barometric pressure
reading.
This must be done with every calibration. To open the relief valve, depress and hold down the
pressure sensor relief valve switch for five seconds, then release.
If you have access to an accurate barometer, you may wish to calibrate the instrument's internal
barometric pressure sensor. This is done using the PC WinLog97 program. Choose
Troubleshooting, Pressure Calibration and an informational message will appear to warn you that
the instrument's current pressure calibration will be lost.
14 English
Figure 1 on page 5 for actual location) to permit the