Dostmann pH 7 Vio Manuel D'utilisation page 25

P3.1 Cell constant Selection
Choosing the right conductivity cell is a decisive factor for obtaining accurate and reproducible
measurements.
One of the fundamental parameters to consider is to use a sensor with the right cell constant in relation to
the solution under analysis.
The following table relates the sensor cell constant with the measurement range and the preferable
standard for calibration:
Access this setup menu to select the cell constant related to the sensor used:
0.1;
•
• 1 -default-;
10;
•
• For each of the 3 selectable cell constants, the instrument stores the calibrated points. By selecting
the cell constant, the previously performed calibration points are automatically recalled.
P3.2 Calibration method
Access this setup menu to select automatic or manual recognition of the standards for performing the
calibration:
AUTOMATIC -default- The device automatically recognizes up to 3 of the following standards
•
84 µS/cm, 147 µS/cm, 1413 µS/cm, 12.88 mS/cm e 111.8 mS/cm;
CUSTOM : the device can be calibrated on a point with a manually entered value.
•
Note: To obtain accurate results, it is advisable to calibrate the device with standards close to
the theoretical value of the solution to be analysed.
P3.3 e P3.4 Temperature compensation in conductivity measurement is not to be confused with pH
compensation.
• In a conductivity measurement, the value shown on the display is the conductivity calculated at
the reference temperature. Therefore, the effect of temperature on the sample is corrected.
On the other hand, when measuring pH, the pH value at the displayed temperature is shown
•
on the display. Here the temperature compensation involves the adaptation of the Slope and
the electrode offset to the measured temperature.
P3.3 Reference Temperature
Conductivity measurement strongly depends on temperature.
If the temperature of a sample increases, its viscosity decreases and this leads to an increase in the
mobility of the ions and the measured conductivity, although the concentration remains constant.
For each conductivity measurement, the temperature to which it refers must be specified, otherwise it is a
result without value. Generally, temperature refers to 25 °C or, more rarely, 20 °C.
Series 7 Vio ENG Version 2.0 April 2020
25
EN