Thermal Microelectromechanical Sensor Construction

Abstract

The problem of constructing a thermal sensor based on the technology of microelectromechanical systems is solved by structural and circuit integration of capacitance-dependent and thermomechanical parts. For this, the use of a MOS transistor (capacitance-dependent part) with a gate in the form of a bimorph membrane (thermomechanical part), which performs cyclic oscillations under the influence of heating from a sensitive element and subsequent cooling, is proposed. The novelty of the proposed sensor is the provision of a frequency-dependent output signal without the use of additional generator circuits. This makes it easier to combine the sensor with digital signal processing systems and reduce the influence of transmission lines on measurement accuracy. Also, the advantages of the sensor include reduced overall dimensions, which is achieved due to the vertical integration of its elements.Model studies of the sensor are carried out and on their basis circuit and software-hardware solutions for determining the temperature of the sensitive element are proposed. It is shown that the use of logarithmic dependence to approximate the influence of the temperature of the sensitive element on the output pulse frequency of the sensor minimizes the measurement error to 3.08 %. The composition of the information and measurement system, which contains a thermal sensor, a sensor signal pre-processing circuit and measurement processing unit using the Atmega328 microcontroller on the platform of the unified ArduinoUno module, is determined. It is shown that the total error of temperature determination in the developed system does not exceed 4.18 % in the temperature range of the sensor element from 20 °C to 47 °C.The program code for the microcontroller part of the information and measurement system is developed, which occupies 12 % of the program memory and 4.9 % of the dynamic memory of the unified module.The proposed thermal microelectromechanical sensor can be used for contact measurement of the temperature of gaseous and liquid media, recording of optical radiation and microwave signal