Xylem ProLab 3000 LABORATORY pH METER - Manual (Page 101)

ProLab 3000 Ion concentration
101 ba75645e02 01/2010
9.3 Calibration
Why calibrate? Ion-selective electrodes age and are temperature-dependent. This
changes the slope. As a result, an inexact measured value is displayed.
Calibration determines the current value of the slope of the electrode
and stores it in the instrument.
Thus, you should calibrate before each measurement and at regular
intervals.
When to calibrate? z Before any measurement if possible
z After connecting another ion selective (combination) electrode
Standard solutions Use two to nine different standard solutions. The standard solutions
have to be selected in either increasing or decreasing order.
In addition to the list with defined values for the standard solutions, you
can enter any concentration for a standard.
Temperature for
calibrating and
measuring
For precise ion selective measurements, the temperature difference
between measurement and calibration should not be greater that 2 K.
Therefore, adjust the temperature of the standard and measuring solu-
tions accordingly. If the temperature difference is greater the [TempErr]
warning appears in the measured value display.
Standard solution (Std 1 -
9) Values
Unit [mg/l] 0.001 ... 500000
Unit [mol/l] 0.010 ... 5000 µmol/l
10.00 ... 5000 mmol/l
Unit [mg/kg] 0.001 ... 500000
Unit [ppm] 0.001 ... 500000
Unit [%] 0.0001 ... 50000
Note
The measurement precision is also dependent on the selected stan-
dard solutions. Therefore, the selected standard solutions should
cover the expected value range of the subsequent concentration mea-
surement.