12 3600 Analyzer for O
2
Measurement—Operator’s Manual
3600O2.OM.E9903
1.3.3 Calibration Menus
As delivered, 3600 systems are pre-calibrated. However, it is recommended that
you recalibrate the oxygen sensor before making any measurements.
The calibration menu permits the calibration of the oxygen sensor, as well as the
instrument’s internal barometric pressure sensor and an optional external pressure
sensor. The calibration menus are shown in the program flow chart in section
1.3.1.
Note that when you select the calibration menu, the instrument discontinues all
measurement operations.
1.3.3.1 Instrument Barometric Pressure Calibration
The instrument’s atmospheric pressure sensor can be calibrated against your own
barometer.
To calibrate, press “ESC” if necessary to bring up the “Measure Options
Calibrate” screen and highlight “Calibrate”, then press “ENTER”. You will see the
menu below:
CALIBRATION
BAROM. PRESSURE
This menu also includes the options of “In Air”, “Direct”, or “Extern. Pressure”.
Press the “ñ” or “ò” key until “Barom. Pressure” is highlighted, and then press
“ENTER” to see the instrument’s atmospheric pressure measurement:
PRESSURE
980 mbar
If this value (the 980 mbar
*
value shown is an example only) is acceptable, press
“ESC” to return to the main “Calibration” menu screen. Otherwise, you can
change the value by pressing “ENTER” to bring up this screen:
BAROMETRIC 0000
PRESSURE ^
Use the “ñ” or “ò” key to increment or decrement the each of the four digits, and
press “ENTER” after each digit to move the cursor one place to the right. The
fourth time “ENTER” is pressed, , the instrument stores the value and then returns
to the previous screen. Again, if this is acceptable, press “ESC”. Otherwise, you
may repeat the process by pressing “ENTER” again and re-entering the numbers.
1.3.3.2 Oxygen Sensor Calibration in Air
Once you are satisfied with the barometric pressure indication, the sensor may be
placed in water-saturated air, to provide a known oxygen reference against which
to calibrate. This is done by unscrewing the sensor storage cap, placing the cap
under tap water, then shaking off the water, leaving a few drops inside the cap.
Before replacing the storage cap, note that the screw-on protection cap should be
in place on the sensor head. (If you use a Dacron mesh inside the protection cap,
make sure it is dry before attempting to calibrate.) Then loosely place the storage
cap back on the sensor, holding it in place by a few turns of its collar. The storage
cap and sensor should now be at about the same temperature.
Now turn to the instrument. With the screen displaying
*
Pressure conversion factors are:
1 bar = 1000 mbar = 750.1 Torr or mm Hg = 29.53 inches Hg = 987 atm = 14.5 psi = 100 kPa.
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