5TE Operator’s Manual
3. Theory
7
Electrical Conductivity
Electrical conductivity (EC) is the ability of a substance to
conduct electricity and can be used to infer the amount of
polar molecules that are in solution. EC is measured by apply-
ing an alternating electrical current to two electrodes, and
measuring the resistance between them. Conductivity is then
derived by multiplying the inverse of the resistance (conduc-
tance) by the cell constant (the ratio of the distance between
the electrodes to their area).
The 5TE uses a 2-probe array to measure the EC. The array is
located on the screws of two of the 5TE prongs.
Small
amounts of oil from skin contact with the screws will
cause significant inaccuracy in the EC measurement
. See
the sensor cleaning section at the end of this manual for
instructions on cleaning the probes if contamination occurs.
The 5TE uses a two electrode array to measure the bulk EC of
the surrounding medium. The bulk EC measurement is cali-
brated at the factory to be accurate within ±10% from 0 to 7
dS/m. This range is adequate for most field, greenhouse and
nursery applications. However, some special applications in
salt affected soils may requires measurements with bulk EC
greater than the specified range. The 5TE will measure up to
23.1 dS/m bulk EC, but user calibration is required above 7
dS/m. Additionally, EC measurements above 7 dS/m are very
sensitive to contamination of the electrodes by skin oils, etc.
Be sure to read sensor cleaning section at the end of the man-
ual if you plan to measure the EC of salty soils.
