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This paper presents a new wide-range sensor for measuring of the gas flow. The flow meter was developed on the base of the new way of measurement, which makes adaptation of measuring procedure. It extends the measurement range of the sensor without losing of accuracy. The sensor is implemented on the basis of the thin-film MEMS structures and the system on a chip, thus minimizing the number of components and to provide a set of standard digital interfaces. A generic aspect of the sensor is an original closed-loop conditioning approach. Using the thermal delay of the temperature waves as a function of gas flow, self oscillations are excited. This "electro-physical" generator realizes an analog-to-frequency conversion of the measuring value. Besides the feedback scheme should improve the sensor performance. The Sensor is made practically on one microcircuit with digital interface due to use PSoC. That has provided high accuracy and low prime cost of the device as a whole.

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.

The dynamic reconfiguration provided by the modern programmable system on chip (PSoC) allows expanding the measuring area and the accuracy of sensors by using the alternative measuring circuits without of an additional external hardware. The reconfiguration is handled internally by the system in order to adjust settings and a measuring method to changing conditions. For example the sensor of the gas pressure with the full scale was designed. In this sensor the analog circuits and the measuring procedure are changed automatically from the steady state thermal conductivity way at vacuum to the temperature waves' method at the highest pressure. Another sensor of gas flow was designed on the base of MEMS and PSoC too. The real-time reconfiguration of SoC's hardware resources allows applying the most suitable circuitry for the broad band measuring.

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