IM 12A06S01-00EN-P
30
NOTE
When a Yokogawa sensor having an ID-chip is used, ITP–type three-point calibration
is not necessary because ITP value of sensor is used as default.
•
ZERO/SLOPE1/SLOPE2 (3points)
This calibration type is the line-segment type three-point calibration. If the relation
between electromotive force and pH is not in proportion for a wide range, divide the
relevant range into two sections and obtain the ZERO (asymmetry) and SLOPE (sensitivity)
in each section to perform calibration.
Limitations
o Three different buffer solutions whose difference in pH value between buffer solutions is
1 pH or more should be used.
(1st buffer < 2nd buffer < 3rd buffer or 1st buffer > 2nd buffer > 3rd buffer)
o The temperature difference between the 1st and 2nd buffer solutions should be 20ºC or
less.
o The temperature difference between the 2nd and 3rd buffer solutions should be 20ºC
or less.
5.2.2 Automatic calibration
Pre-select the buffer solution to be used, for details see section 4.1.9.
Calibration can be set the same as for manual calibration:
•
ZERO/SLOPE
Select the solution that works with the “buffer solution” selected in calibration settings and
perform calibration using the HOST system.
•
ZERO/SLOPE/ITP
Calibration is performed in a sequence (predefined by HOST) of the solution that works
with the “buffer solution” selected in calibration settings. Perform calibration using the
HOST system.
Limitations:
o Temperature during calibration must be within the limits of the selected buffer table.
o Three different buffer solutions whose difference in pH value between buffer solutions is
1 pH or more should be used.
(1st buffer < 2nd buffer < 3rd buffer or 1st buffer > 2nd buffer > 3rd buffer)
o The 2nd buffer solution should be pH 7 ± 2 (at 25°C).
o Either of the following conditions should be met:
- The temperature difference between the 1st and 2nd buffer solutions should be 20ºC
or less. The temperature of the 1st and 2nd buffer solutions is at least 20ºC higher or
lower than the temperature of the 3rd buffer solution.
- The temperature difference between the 2nd and 3rd buffer solutions should be 20ºC
or less. The temperature of the 2nd and 3rd buffer solutions is at least 20ºC higher or
lower than the temperature of the 1st buffer solution.
5.2.3 Sample calibration
A sample calibration is a single-point calibration for only the ZERO (asymmetric). It adjusts
the calculated output for pH to a collected sample value. Use the HOST to record a
collected sample and to set SA11.