RADIOMETER ABL800 FLEX, Справочное руководство

Страница: 15 / 206

1. Potentiometric measuring principles ABL800 FLEX Reference Manual
pH electrode,
Continued
Designation
(continued)
pH(Cal1,nom)
= Nominal pH of Cal 1 solution (pH = 7.4)
pH(Cal1)
= pH of Cal 1 solution
E(pH,Cal1prev) = Potential of the pH electrode chain from the previous
calibration measurement on Cal 1 solution
Sens(pH,prev)
fraction
= Sensitivity of the pH electrode from the previous 2-point
calibration
pH(Cal1,prev)
= pH of Cal 1 solution in the previous calibration
measurement
pH(Cal2)
= pH of Cal 2 solution
Sens(pH)
= Relative sensitivity of the pH electrode chain.
Sensitivity The sensitivity of the pH electrode (Sens
pH
) is obtained from the calibration line
obtained from a 2-point calibration on Calibration Solutions 1 and 2 (Cal 1 and Cal
2), and is calculated from the following equation:
[ ]
pH(Cal1) pH(Cal2) 61.5
Cal1) E(pH, Cal2) E(pH,
Sens(pH)
− × −
−
=
(fraction)
The sensitivity of the pH electrode should fall between 0.92 - 1.03 or 92 -103 %.
Status The status of the pH electrode is calculated from the following equation:
pH(Cal1) nom) pH(Cal1, 2
61.5 -
Cal1) (pH, E Cal1) E(pH,
Status(pH)
0
− +
−
=
The status of the pH electrode should fall between a pH of 6.7 and 8.1.
Drift Drift 1 is calculated from the following equation:
[ ]
prev) pH(Cal1, pH(Cal1)
prev) Sens(pH, 61.5 -
Cal1prev) E(pH, Cal1) E(pH,
1(pH) Drift
− −
×
−
=
NOTE: Under normal circumstances, pH(Cal1)
−
pH(Cal1,prev) = 0. However in
instances where the Cal 1 solution container has been replaced between two
consecutive calibrations,
pH(Cal1)
−
pH(Cal1,prev)
≠
0 .
The default drift tolerances set by Radiometer for Drift 1 are
±
0.020.
Drift 2 is calculated from the following equation:
[ ]
Drift 2(pH)
E(pH, Cal2) E(pH, Cal1prev)
- 61.5 Sens(pH, prev)
pH(Cal2) pH(Cal1, prev)
=
−
×
− −
The default drift tolerances set by Radiometer for Drift 2 are
±
0.020.
Continued on next page
1-10