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DOTX-45 Dissolved Oxygen System Part 7 –Calibration

DOTX-45 48 -

2. Cover the sensor, if necessary, to shield it from the direct rays of the sun.

Remember, the membrane must not be submerged - it must be in the air

letting the sensor hang, membrane downward, while powered.

3. Allow the system to operate undisturbed for at least 20 minutes. If the system

is stable, the value on the display will increase to some PPM value and

remain at that level. At that point, calibration can continue.

4. Scroll to the CAL menu section using the MENU key and press ENTER or the

UP arrow key. Cal D.O. will then be displayed.

5. Press the ENTER key. The screen will display a flashing 1-spl for 1-point, a

%-sat for Saturation air calibration, or a 3-zer for zero calibration. Using the

UP arrow key, set for a 3-sat span calibration and press ENTER.

6. The display will prompt the user to hold the sensor in air and press ENTER. If

the sensor has already been removed from the process and reached

temperature equilibrium, press the ENTER key.

7. The system now begins acquiring data for the calibration value. As data is

gathered, the units for ppm and temperature may flash. Flashing units

indicate that this parameter is unstable.

8. The calibration data point acquisition will stop only when the data remains

stable for a pre-determined amount of time (approximately 15-20 seconds.)

This can be overridden by pressing ENTER. If the data remains unstable for

10 minutes, the calibration will fail and the message Cal Unstable will be

displayed.

9. If accepted, the screen will display the message PASS with the new sensor

slope reading, then it will return to the main measurement display. If the

calibration fails, a message indicating the cause of the failure will be

displayed and the FAIL icon will be turned on.

10. The range of acceptable values for sensor slope is 20% to 250%. It may be

necessary to rebuild the sensor as described in section 5, Dissolved Oxygen

Sensor Assembly.

Should the slope value remain out of range and result in calibration failures,

review the Service Section of this manual.

7.14 Dissolved Oxygen Zero Cal

Dissolved oxygen sensors have extremely low offset outputs at zero. For this

reason, it is normally sufficient to simply leave the zero at the factory default of 0

mV. As an alternative, an electronic zero can be set by disconnecting the sensor

from the cable and performing the steps below.

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Dot-x SERIES Specifiche Pagina 49