LaMotte CDS 5000 Conductivity Meter - Manual (Page 5)

METER BASICS
Conductivity is measured using a probe which contains two electrodes,
separated by a fixed distance. When a voltage is applied from the meter
across the electrodes, the ions in solution conduct a current, which flows
between the electrodes. The greater the concentration of ions in the
solution, the larger the current generated and the higher the conductivity.
Likewise, the smaller the concentration of ions, the lower the
conductivity. The meter converts the current measured to a conductivity
reading.
Over time the electrodes may become dirty or fouled with contaminants
from the sample. For specific probe cleaning instructions for the CDS
5000 see Maintaining The Meter on page 13.
Conductivity measurements are very dependent on temperature. The
ability of the ions to move through the solution, and conduct the current,
is related to the temperature of the solution. As the temperature rises, the
ions move more quickly through the solution, increasing the conductivity;
likewise as the temperature decreases the ions move more slowly and the
conductivity decreases. Since the conductivity of the same solution can
change by as much as 2%/°C, accurate temperature measurements must
be made simultaneously to the conductivity reading. The CDS 5000
includes a temperature probe to measure the temperature.
To make conductivity readings taken at different times and places
comparable, measurements are often converted to what the conductivity
of the solution would be at 25°C. The CDS 5000 automatically makes this
conversion before providing a final reading.
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