The geometry of TICS has an influence on the output signal of sensors. This relation is determined by the cell constant given by the size of a sensor.

Several researchers demonstrated three methods to determine the cell constant of TICS― experimental method using standard solutions with known conductivity, single-loop calibration method and analytical method by rough approximation. They pointed out that in order to measure the lower ranges of conductivity which require a smaller cell constant, the diameter of sensor and measuring container must be enlarged.

But until now it has not been suggested to deal with the influence of the geometric parameter of a sensor on the cell constant and the regulation band of the cell constant with the size of a sensor. So, it is worthwhile to do some research on the relation between the cell constant and the size of a sensor.

Jang Hyon, a researcher at the Faculty of Electronics, has analyzed the relation between the geometry of a TICS (inner radius *r*_{1}, outer radius *r*_{2} and height *t* of the sensor toroid) and its cell constant through simulations by the finite element method and experiments.

Taking account of actual conditions, he considered the sizes (*r*_{1}, *r*_{2} and *t*) of a sensor within several tens of millimeters.

A key factor which influences the cell constant is the hole diameter (2*r*_{1}) 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.

The theoretical results on the cell constants of sensors in different sizes coincided with the experiment results with less than about 5% relative error.

The conductivity below limit value that can be adjusted by cell constant is about 0.36 times the lowest bound value of conductance measurement range.

You can find the details in his paper “Optimization of the cell constant for application of the transformer type inductive conductivity sensor (TICS) in low-conductive solution” in “IEEE Sensors Letters” (SCI).

© 2021 KumChaek University of Technology