Yokogawa PH72 Personal pH/ORP Meter - Manual (Page 75)

IM 12B03D02-01E 9-8
9. Technical Information
9.7 Calibration Calculation
The PH72 meter is calibrated at 2 points using 2 standard solutions. The first calibration
is done so a certain line is drawn through the calibration point (Figure 9.9). The second
calibration is done so a line is drawn through the first and second calibration points
(Figure 9.10). One-point calibration is a simplified method where only the first
calibration of 2-point calibration is performed.
Note: A calibration point is the emf corresponding to the pH value of a standard
solution used. (Refer to Table 4.1.)
pH0
pH14
F0909.EPS
pH7, 0mV
+mV
-mV
Calibration line
Theoretical line
Calibration point
Figure 9.9 Calibration at First Point
pH0
pH14
pH7, 0mV
+mV
-mV
Second
calibration point
Theoretical line
First
calibration point
Calibration line (slope)
Asymmetry potential
F0910.EPS
Figure 9.10 Calibration at Second Point