In this article, we propose the idea of ​​creating a complex sensor for measuring the dielectric parameters of liquid substances in order to distinguish samples with small changes in the parameters in low-microwave ranges. The measurements are carried out by a capacitive method. For measurement at a low frequency, a capacitor-to-code converter is used; in the microwave method, a vector analyzer is used for the measurement. As a capacitive sensor, a interdigital capacitor is used that has geometrical and electrophysical parameters, in which it is not a radiating structure in the range of controlled frequencies. To combine the low-frequency and microwave methods in one sensor, a frequency-isolation scheme is used. The urgency of the method lies in the absence of the need for separate measurements of the sample with the help of various sensors.

Keywords: interdigital capacitor, coaxial probe, frequency isolation circuit, liquid substance, sensor, model, reflection coefficient, electrical capacitance, capacitor-code converter