Calibration For Ion Selective Measurements - wtw pH/ION 340i Operating Manual

Operation
Why calibrate?
When to calibrate?
ConCal
AutoRead
34
1 Activate the AutoRead function with <AR>.
The current measured value is frozen (hold function).
2 Start AutoRead with <RUN/ENTER>.
AR flashes until a stable measured value is reached.
This measured value is transmitted to the interface.
3 If necessary, start the next AutoRead measurement with
<RUN/ENTER>.
4 To terminate the AutoRead function: Press the <AR> key.
Note
The current AutoRead measurement can be terminated at any time
(accepting the current value) by pressing <RUN/ENTER>.

4.4.3 Calibration for ion selective measurements

Ion sensitive 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 measuring instrument.
Thus, you should calibrate before each measurement (if possible), and
at regular intervals.
Note
For calibration, use tempered standard solutions with a temperature
that differs by maximum
ple.
l Before each ISE measurement if possible
l After connecting another ion selective electrode or reference elec-
trode
l When the sensor symbol flashes after a voltage interruption, e.g.
battery change
This is the conventional two-point or three-point calibration procedure
that uses 2 or 3 freely selectable standard solutions. The concentration
expected for the measurement determines the concentration of the cal-
ibration standards.
The calibration procedure automatically activates the AutoRead func-
tion. To accept the current measured value without waiting for the Au-
toRead function to finish, just press <RUN/ENTER>.
±
2 °C from the temperature of the test sam-
pH/ION 340i