Xylem ProLab 4000 - Manual (Page 74)

pH ProLab 4000
74 ba75646e03 12/2012
7.3 Calibration
Why calibrate? pH electrodes age. This changes the zero point (asymmetry) and slope
of the pH electrode. As a result, an inexact measured value is dis-
played. Calibration determines the current values of the zero point and
slope of the electrode and stores them.
Thus, you should calibrate at regular intervals.
When do you have to
calibrate?
 After connecting a non-ID electrode
 After the CalClock has expired
Buffer sets for
calibration
You can use the buffer sets quoted in the table for an automatic calibra-
tion. The pH values are valid for the specified temperature values. The
temperature dependence of the pH values is taken into account during
the calibration.
No. Buffer set * pH values at
1 DIN
DIN buffers according to DIN 19266
and NIST Traceable Buffers 1,679
4,006
6,865
9,180
12,454
25 °C
2 TEC 2,000
4,010
7,000
10,011
25 °C
3 Merck1 * (Technical buffers) 4,000
7,000
9,000 20°C
4 Merck2 * 1,000
6,000
8,000
13,000
20°C
5 Merck3 * 4,660
6,880
9,220 20°C
6 Merck4 * 2,000
4,000
7,000
10,000
20°C
7 Merck5 * 4,010
7,000
10,000
25 °C