Sensor Calibration - Hach ORBISPHERE3650 Manuel D'utilisation De Base

Change from the instrument
1. Switch the instrument power OFF
2. Switch the instrument on by holding down the Down Arrow button and then pressing the
POWER button while still pressing the Down Arrow button
3. The instrument will first display USE followed by either dIS for dissolved phase measurement in
liquids or gAS for gaseous phase measurement
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
Calibration
Pressure calibration
Since the instrument is sealed against moisture, you must open the barometric pressure sensor relief
valve switch on top of the instrument to permit the 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 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.
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.

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
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 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.
on page 14 for more details).
Entering a span gas value
on page 14 for details).
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