In order to measure the concentration of an electrolyte solution, especially the salt gradient in a solar pond in which the salinity is changed continually, the C.E.T. sensor and its special circuit were developed on the basis of the electroconductivity-temperature measurement method, by which the salt gradient could be measured quickly at any experimental site. Based on a thorough analysis of the conventional sensor with needle electrodes, the C.E.T. sensor effectively overcame the fault (wall-approach-effect) of the conventional sensor with a special structure formed by several cylindrical electrodes and a shield plate on the top. Here, the circuit was designed to obtain high S/N signals and a relation function with a high multiple correlation coefficient of 0.998 was obtained to adapt the wide ranges of concentration 0 similar to 20 wt% and temperature 10 similar to 80 degreesC on measuring electrolyte-solution concentration. The applicability of the C.E.T, sensor was verified and a new design and measurement method was described in this research. (C) 2001 Published by Elsevier Science Ltd.