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1. Remove the sensor from the process liquid. Use a soft tissue and a stream of water from a wash bottle to clean
the membrane. Blot dry. The membrane must be dry during air calibration.
2. Pour some water in a beaker and suspend the sensor with the membrane about 0.5 inch (1 cm) above the
water surface. To avoid drift caused by temperature changes, keep the sensor out of the direct sun.
3. Monitor the dissolved oxygen reading and the temperature. Once readings have stopped drifting, begin the
calibration. It may take 5 - 10 minutes for the sensor reading in air to stabilize. Stabilization time may be even
longer if the process temperature is appreciably different from the air temperature. For an accurate calibration,
temperature measured by the sensor must be stable.
7.3 CALIBRATING THE SENSOR IN AIR
MODEL 54eA SECTION 7.0
CALIBRATION - DISSOLVED OXYGEN
4. From the main display, press any key to obtain the main menu. With the
cursor on “Calibrate,” press Enter (F4).
NOTE
If Hold was enabled in Section 5.6, the hold screen will appear. To
activate hold, refer to Section 5.6, step 11.
Press Enter (F4). The screen shown in step 5 appears.
5. Press Enter (F4) to select “Calibrate in air.”
6. This screen shows the barometric pressure and temperature that will
be used for the calibration. If the barometric pressure or temperature is
incorrect, press Abort (F1). Refer to Section 7.5 for the pressure cali-
bration procedure. Refer to Section 6.2 for the temperature calibration
procedure.
NOTE
The barometric pressure sensor is inside the controller enclosure.
When cable glands are in place and the front panel is tightly closed,
the enclosure is moderately airtight. Therefore, as the controller
heats or cools, the pressure of the air trapped inside the enclosure
may be different from ambient. Opening the front panel will equal-
ize the pressure.
7. Press Cont (F3). “Wait” flashes until the sensor is stabilized. Once air
calibration is complete, the message “Air calibration done” appears.
The display will show the equilibrium solubility of atmospheric oxygen
in water at the prevailing temperature and pressure.
procedure continued on next page . . .
Calibrate main sensor
Zero main sensor
Adjust temperature
Exit Enter
Calibrate in air
Calibrate in process
Barometric pressure
Exit Enter
Bar press : 760 mmHg
Temperature: 25.0°C
Press F3 to air cal
Abort Cont
8.20 ppm
Stabilizing . . . Wait
Abort Cont
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