Single Point Calibration (S - ABB AW400 Series Instruction Manual

Put the two standard buffer solutions in two beakers in a sufficient amount to cover the sensor. Wash the
probe with de-mineralised water, dry it and dip it in the standard pH 7 buffer solution. Stir softly but
continuously the probe: in this way a lower stabilisation time will be required.
Press the MENU key to enter the Instrument Calibration submenu and enter the CALIBRATION menu and
then the channel of the pH probe. The display will show:
P1 indicates the first point of calibration at HIGHER pH (pH 7). XX.XX is not a REAL pH value, but it shows
when stability of measure has been reached. YY.Y is a value set at the last calibration and can be freely
modified according to the chosen buffer solution. Press ENTER and insert the correct value. Wait 3 minutes
after the measure in XX.XX has stabilised (XX.XX is stable), then press ENTER to save the value (press END
if you don't want to save the value).
If the following message appears:
It means the buffer solution is bad since the mV generated are too close.
Pass on to the second point (P2) of calibration pressing the MENU key. Take the sensor out of the 7 standard
buffer solution, rinse it thoroughly with de-mineralised water, dry it and immerse it in the 4 pH std buffer
solution. Stir softly but continuously the probe: in this way a lower stabilisation time will be required. Wait till
the value in XX.XX is stabilised (XX.XX is stable) and correct the pH value in YY.Y. Confirm by pressing the
ENTER key. Previously stored values are overwritten in not volatile memory. To start the measure press the
END key and the display will show the actual measured value.
6.1.3.2 Single point calibration (S.P.C.)
The single point calibration may be performed ONLY IF A DOUBLE POINT CALIBRATION HAS ALREADY
BEEN PERFORMED. The single point calibration is a fast procedure to correct the sensitivity of an instrument
leaving it working in field; however it's less accurate than the double point calibration and must be performed
as near as possible to the pH value of the process liquid. The single point calibration corrects the intercept of
the pH = f(mV) curve, but doesn't vary its slope.
To perform the single point calibration, measure the pH value of the process fluid near the location of the
sensor (if it is constant during the time interval needed for the calibration). Insert the pH value in YY.YY.
Entering the Calibration menu the following display will appear:
46
X X . X X p H
P 1 :
-Bad Input!-
X X . X X p H
p H S P C :
2 3 . 5 ° C
Y Y . Y
2 3 . 5 ° C
Y Y . Y Y