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BKI 11 ATEX 0012 X
6.6.
DO
S
ENSOR CALIBRATION
This function is for periodic calibration of the DO sensor.
The sensor is aging during the usage of the instrument. When the life-time of the sensor is over the sensor should be replaced. In case of sensor replacement the
sensor should be calibrated compensating the aging. Calibration of the sensor has to be done in two points: (ZERO – zero point and SPAN – saturated value)
ZERO calibration can be performed with 5% sodium sulphite referential liquid, SPAN (saturated value) calibration can be performed with saturated zero salinity
referential liquid or air. Value of atmospheric pressure should be set before calibration process (see 6.4.1.8.)
Entering the SERVICE / SENSOR CALIBRATION menu the instrument will display a warning message that the user is about to change critical parameters of the
measurement system. The user can enter the menu by pressing the (OK) button or exit to the previous menu by pressing the (NO) button.
In case of calibration, after sensor replacement, please handle first calibration with high priority. The system will inquire this in the next dialog box. In the event of
initial calibration, press the OK button. In this case, all parameters and counters related to the sensor will be reset to default.
We should press NO button, in case it is not the first calibration.
6.6.1.
Calibration of saturated value (100%)
(SERVICE / SENSOR CALIBRATION / CAL. IN AIR (SPAN))
Rinse the DO sensor with distilled water then dry up gently using a soft rag. Immerse the sensor into
saturated, zero salinity referential liquid or hold the sensor into air.
Please wait until the measured value (2) get stabilized. Change in the measured value (2) can be
followed on the trend bargraph (1). Achieving proper calibration atmospheric pressure (3) and
relative humidity (4) should be entered. In accordance to these values and the measured
temperature the instrument calculates the DO concentration, which can be edited in the last line (5).
Damping check:
When pressing the
E
button at the last line, a warning message appears asking do we really want
to store the calibration data. By pressing the [yes – OK] button, the instrument checks the stability
of the measured value and if it remains unchanged during a given time period, the instrument stores
the calibration. Changes of the measured value can be checked on the display (2) and the trend
bargraph (1) also indicates changes of the measured value. When the measured value got
stabilized, READY! message will appear on the bottom of the screen. If damping check procedure is
unsuccessful, FAILED! message will appear on the bottom of the screen. When the error caused by
changes or fluctuations became resolved, then calibration-point storing procedure can be repeated.