Simulation of a Gas Flow Sensor Based on ThinFilm Thermistor Elements Taking into Account the Effect of Thermal Correction

Due to increased demand in the biomedical equipment sector, need for gas consumption assessment systems is naturally growing. The purpose of this study is to obtain a model of a hot-wire gas flow sensor to study the influence of the material of the thermistor of the sensor on the power required for its operation. Its operating principle is to maintain a constant temperature of the bridge thermistor system relative to the reference resistor by supplying current to heat the bridge. The TaN protected FeNi thermistor system is located on a SiO2/Si3N4/SiO2 multilayer membrane to prevent heat dissipation through the silicon crystal that serving as the basis for sensitive element. The novelty of the proposed sensor is in the geometric shape of the thermistors, as well as in the choice of the main material of the thermistors. FeNi was used to reduce the cost of the device. The choice of FeNi is also due to its high resistivity temperature coefficient. Experimental samples of gas flow sensor with NiFe-based thermistor material were fabricated using thin-film membrane technology. The model of gas flow sensor was built in COMSOL Multiphysics and verified by comparing the calculated output signal with the operating parameters of the fabricated experimental samples. It was shown that simulation results agreed well with the experiment, demonstrating a discrepancy with the calculation of less than $10 \%$ with an average level of sensitivity to gas flow measurement of about 50 $\mathrm{mV} /(\mathrm{m} / \mathrm{s})$ in the speed range varied from 0 to $19 \mathrm{~m} / \mathrm{s}$.