Self-Oscillating Parametric Humidity Sensor With Frequency Output Signal

Abstract

A self-oscillating parametric humidity sensor has been developed that implements the principle of "humidity-frequency" conversion into hybrid integrated circuit based on a microelectronic transistor structure with a negative differential resistance, in which the humidity-sensitive element is a resistor of the HR202 type. For the purposes of determining parameters self-oscillating parametric humidity sensor with frequency output a mathematical model has been developed that takes into account the effect of humidity on a sensitive resistive element, which is an integral element of the device. Based on the mathematical model, analytical expressions for the transformation function and the sensitivity equation are obtained. It is shown that the main contribution to the conversion function is made by relative humidity. The computer simulation and experimental studies of a self-oscillating parametric humidity sensor with a frequency output signal contributed to obtaining the main parameters and characteristics, such as the dependence of the generation frequency on changes in relative humidity in the range from 30% to 99%, the change in sensitivity on relative humidity, the dependence of the active and reactive components of the impedance in the frequency range from 50 kHz to 2 GHz; standing wave ratio, change in logarithmic magnitude and spectra of the output signal of a parametric humidity sensor with a frequency output signal in the LTE-800 Downlink frequency range. The obtained electrical characteristics confirm the operability of the developed device. The sensitivity of the developed self-oscillating parametric humidity sensor in the range of relative humidity change from 30% to 99% has a value from 332.8 kHz/% to 130.2 kHz/%.