YOKOGAWA PH72-21-E-AA, User Manual

Page: 33 / 112

IM 12B03D02-01E
4-6
4. Calibration
4.2 Manual Calibration
When using standard solutions other than those preprogrammed for automatic calibration
(see Section 4.1), calibration should be performed manually.
In 2-point calibration, manual calibration can be performed at both two points or manual
calibration performed at one point (either 1st or 2nd) in combination with automatic
calibration using a specified standard solution at the other point.
Note: Although manual calibration can be performed using standard solutions the same
as the ones preprogrammed for automatic calibration, it only makes the
procedure more complicated. When using these standard solutions, automatic
calibration should be generally performed.
d
Precautions
(1) The difference between the pH values of two standard solutions to be used for 2-
point calibration must be at least 0.7 pH. If not, the meter will recognize the two
standard solutions as the same calibration point. That is, the second calibration
result will override the first calibration value, resulting in 1-point calibration.
(2) When using alkaline standard solutions, use the standard solution with lower pH
for the first point calibration. If not, may appear.