Optimization of the Cell Constant for Application of the Transformer Type Inductive Conductivity Sensor (TICS) in Low-Conductive Solution

In this letter, the relation between geometry of a transformer type inductive conductivity sensor (TICS) (inner radius r
₁
, outer radius r
₂
, and height
t
of the sensor toroid) and its cell constant is presented through simulation analysis by the finite element method and experiments. Taking account of actual condition, sizes (r
₁
, r
₂
, and
t
) of the sensor are considered within several tens mm. A key factor which influences on the cell constant is a hole diameter (2
_r1
) of the sensor toroid. The effective superior limit of inner radius of the sensor toroid that can give the smallest cell constant is about 30 mm. Theoretical results on the cell constants of sensors with different sizes corresponded to the experiment results with less than about 5% relative error. Conductivity below limit value, which can be adjusted by cell constant is about 0.36 times of the lowest bound value of conductance measurement range.