Yokogawa SPS24 - Manual (Page 22)

<3. Sensor Management>
3-5
IM 12A01S02-01E 1st Edition : May 10, 2013-00
Limitations
• 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)
• The temperature difference between the 1st and 2nd buffer solutions should be 20ºC or
less.
• The temperature difference between the 2nd and 3rd buffer solutions should be 20ºC or
less.
Table 3.4 Buffer selection for 3-point calibration
Buffer for 3-point Calibration Buffer Sequence
NIST/DIN19266 pH1.7→pH6.9→pH9.2
pH4.0→pH6.9→pH9.2
pH9.2→pH6.9→pH1.7
pH9.2→pH6.9→pH4.0
DIN19267 pH4.7→pH6.8→pH9.2
pH9.2→pH6.8→pH4.7
US pH4.0→pH7.0→pH10.0
pH10.0→pH7.0→pH4.0
User setting Buffer Table 1 → Buffer Table 2 → Buffer Table 3
Buffer Table 3 → Buffer Table 2 → Buffer Table 1
* In 2-point calibration, set the sequence for each buffer.
n Temperature Calibration (Temperature Setting)
For the most accurate measurements, it is important to have a precise temperature
measurement. Measure the temperature with a high-precision thermometer and adjust the
sensor reading accordingly. For best accuracy, this should be done as near to the normal
operating temperature as possible.
n ORP Calibration (rH Calibration)
No automatic calibration feature is available in an ORP or rH calibration.
Calibration is performed stepwise. Follow the prompts displayed on the screen.
A stability check is made at each measurement point. Proceed to the next step only after the
reading has stabilized.