Gas Density Sensor Based on PSoC5

Abstract

A significant part of all types of measurements performed in modern industry and science are measurements of gas, liquid or other media. This is important because there are many processes where you need to clearly control the parameters of the environment - pressure, density, etc. The object of research are MEMS gas density sensors. The subject of the research is to eliminate the shortcomings of existing similar systems, increase the accuracy of measurement and range of measured gas pressures and safe operation of the system in critical conditions. The aim of the work is to implement a gas density sensor based on a crystal, using auxiliary functional modules, to monitor the operation of the system and to obtain a sophisticated functional device that will be easy to use. Several prototypes are considered, where a miniature cantilever is used as a sensitive element. The disadvantage of such systems is that the accuracy of measurement depends on the support of the cantilever and the gas pressure. Also in the prototype [3] it is noted that the measurement time of one sample lasts about 2 minutes, which is very significant. In the course of work the methods of determination of thermophysical parameters of the environment with use of primary converters on MEMS technology which are made on structure of a heater, a sensitive element and passive components are analyzed. Calculations for determination of gas density are also described. The implementation of a complete, functional sensor for measuring gas parameters based on a programmable system on a crystal based on Cypress PSoC 5 is considered. This system allows us to implement a complex measuring device on almost one crystal because this system has in its structure a certain set of already built-in analog and digital units. The main advantage of PSoC5 is the ability to dynamically reconfigure the system during operation. That is, having one set of elements, we can build on it a number of different schemes without stopping the measurement process. PSoC Designer software configures built-in units such as DAC, iDAC, ADC. The configuration of these units and connection to them of external elements, such as thermistors and a thermal heater are given. Simulation of the given scheme is carried out and results in a graphic kind are resulted. The main principle of the device is the dependence of temperature attenuation on the environment. The idea is to compare the phase shift between two harmonic signals. One signal is a reference signal, and the other is a signal that is recorded by a thermal sensor after the temperature wave passes through the measuring medium. Since this signal will pass with a certain delay then the phases of the reference signal and the measured will be shifted. Therefore, the phase difference between these signals will depend on the density of the medium through which the heat wave passes. In the conclusion of work both advantages and lacks of the offered method which have been proved on the basis of comparison with other already known similar methods are considered.