RU2406985C1 - Pressure measurement device based on nano- and micro-electromechanical system having frequency output - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: pressure measurement device based on a nano- and micro-electromechanical system, having a frequency output which has a strain gauge consists of a housing in which there is a nano- and micro-electromechanical system with an elastic member in form of a membrane having a base on which there is a heterogeneous structure made from thin films of materials in which there are tensoresistors joined into a tensobridge, a frequency converter for the signal from the output of the tensobridge, having a comparator and an integrator. The integrator is made on an operational amplifier with a first capacitor in a negative feedback circuit whose output is connected to the first input of the comparator, between whose output and the inverting input of the operational amplifier of the integrator of which a second capacitor is connected. The inverting input of the operational amplifier of the integrator is connected through a first resistor to one vertex of the measuring diagonal of the tensobridge, and the other vertex is connected to the non-inverting input of the operational amplifier of the integrator and the second input of the comparator. There is voltage divider comprising two resistors, a second resistor of the integrator and an extra resistor. The voltage divider is connected in parallel to the power diagonal of the tensobridge of the sensor. The output of the voltage divider is connected through the second resistor of the integrator to the inverting input of the operational amplifier of the integrator. The first vertex of the power diagonal of the tensobridge is connected through the extra resistor to the output of the comparator, and the second vertex is connected to an earth bus. The extra resistor consists of two parts.

EFFECT: broader functionalities of the pressure measurement device based on a nano- and micro-electromechanical system, having a frequency output, and high accuracy of converting a disbalance signal of the tensobridge of the sensor owing to reduced effect of tensoresistor heating temperature on the output signal.

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Description

The invention relates to measuring equipment and can be used to measure pressure under the influence of the temperature of the measured medium, both in automatic control systems and in digital devices of special and universal purpose.

Known strain gauge pressure sensors with strain gauges located on the membrane in the radial direction and connected to a bridge measuring circuit [1, 2]. Their common drawback is the low accuracy under the influence of the temperature of the measured medium, they require additional thermocompensation elements (thermistors) and their adjustment. This is due to the appearance of a temperature gradient along the radius of the membrane, the presence of a temperature coefficient of resistance of the strain gauges, uneven heating of the strain gauges and its parts. As a result, an imbalance of the bridge measuring circuit appears that is not related to the measured pressure, the accuracy of the pressure measurement is sharply reduced. The error from the influence of temperature can reach 30-60%, while under normal conditions an error of 0.5-1.5% is ensured.

Known strain gauge pressure sensor [3], the basis of which is a thin-film nano- and microelectromechanical system (NIMEMS) with a heterogeneous structure. By heterogeneous structures in the general sense we mean structures that are heterogeneous in their composition or origin (belonging to one form or another, type, group, class, system). Sensors of this type relate to products of nano- and microsystem technology [4].

The strain gauge pressure sensor [3] contains a vacuum housing, a thin-film nano- and microelectromechanical system, consisting of an elastic element in the form of a round rigid-clamped membrane made in one piece with the base, on which circumferential and radial strain gauges connected to the bridge circuit are located. They are made in the form of identical strain gauges connected by low-resistance jumpers and uniformly placed along the periphery of the membrane. Each of them touches with two vertices of the membrane boundary. The dielectric is made in the form of a Cr-SiO-SiO ₂ thin-film structure, the strain elements are in the form of an X20H75Y structure, and the bridges are in the form of a V-Au structure.

Since the strain elements are identical and are located on the periphery of the membrane at the same distance from its center, then despite the temperature change on the planar side of the membrane, the temperature of the strain elements of the circumferential and radial strain gauges, changing, will be the same at each time point. The identical temperature of the radial and circumferential strain gages at each moment of time causes almost the same changes in the resistance of the strain gages, which due to the inclusion of the strain gages in the bridge circuit are mutually compensated.

The disadvantage of pressure measuring devices containing these pressure sensors and signal converters with an analog output is that they are highly sensitive to instability of the voltage supply of the strain gage, have a temperature error associated with the heating of the strain gages of the bridge, both from the influence of the temperature of the environment and the medium being measured, and from current passage.

A known converter [5] of the strain gage unbalance signal to a frequency, comprising a strain gage, a comparator, the output of which is connected to the power supply diagonal of the strain gage, and an integrator made on an operational amplifier with a first capacitor in the negative feedback circuit, the output of which is connected to the first input of the comparator, between the output a second capacitor is connected to the comparator and the inverting input of the integrator operational amplifier, the integrator input is connected to one of the vertices of the measuring diagonal of the tensor bridge, and its other vertex and connected to a non-inverting input of the operational amplifier of the integrator and the second input of the comparator. The converter contains a strain gauge bridge, an integrator on an operational amplifier with a capacitor in the negative feedback circuit, a comparator whose output is connected to the diagonal of the strain gauge power supply and connected through a capacitor to the inverting input of the amplifier, the first input is connected to the integrator output, and the second input to one of the measuring vertices the diagonal of the strain gage and to the non-inverting input of the amplifier. The other vertex of the measuring diagonal of the bridge is connected to the input of the integrator. The output frequency of this converter is determined by the formula

where ε _R is the relative change in the resistance of the strain bridge from the effects of the measured pressure; R _and - the resistance of the integrator 16, which includes the output resistance of the strain gauge bridge 15 and the resistance of the cable line; C ₂₀ - capacitor 20.

As can be seen from formula (1), the frequency of the output signal of the converter is determined by the resistance of the integrator R _and including the output resistance of the strain gauge bridge and the resistance of the cable line, the capacitance of the capacitor C ₂₀ and the relative change in the resistance of the strain bridge ε _R from the influence of the measured pressure, but does not depend on supply voltage. However, formula (1) is valid for this device in the case when the operating temperature of the strain gage does not undergo significant changes, and the converter only works when the strain gage is unbalanced in one direction, and when the imbalance is in the other direction, and even with zero imbalance, the circuit “falls asleep”, those. the output frequency of the converter is zero.

где

- относительное изменение сопротивления тензометрического моста при изменении температуры, U₀ - напряжение питания тензомоста.Under real conditions of operation of pressure sensors with long and continuous operation time and insufficient heat removal, the operating temperature of the strain gage can change due to heating during current flow through the strain gages, as well as due to a change in the temperature of the medium being measured, and then the resistance of the strain gages included in the bridge circuit and the resistance the strain gauge bridge as a whole will vary in proportion to the temperature in accordance with the value of the temperature coefficient of resistance, which, when Yeru for metalloplenochnyh strain gages is of the order 3 * 10 ^-3% / 10 ° C. In this case, the unbalance voltage from the output of the measuring diagonal of the tensor bridge will be not εU ₀ , but

Where

- the relative change in the resistance of the strain gauge bridge when the temperature changes, U ₀ - voltage supply of the strain gage.

Then the formula (1) is converted to the form:

As can be seen from expression (2), the frequency of the converter output signal will decrease with increasing temperature. The relative temperature error can reach 2% or more.

Thus, the disadvantages of the device containing the strain gauge pressure sensor and the frequency converter of the signal from the output of the strain gauge bridge are low accuracy when the resistance of the strain gauges changes with the temperature of the heating of the strain gage and the converter operates only when the strain gage is unbalanced in one direction, i.e. “Falling asleep” scheme with unbalance in the other direction and with zero unbalance.

The technical result of the invention is to expand the functionality of a pressure measuring device with a frequency output based on a nano- and microelectromechanical system (NIMEMS) and to increase the accuracy of converting the strain gauge bridge imbalance signal by reducing the influence of the heating temperature of the strain gauges on the output signal.

This goal is achieved by the fact that in the known device for measuring pressure with a frequency output based on a nano- and microelectromechanical system (NiMEMS) containing a strain gauge sensor, consisting of a housing installed in it NiMEMS with an elastic element in the form of a membrane with a base formed on it a heterogeneous structure of thin films of materials in which strain gages are formed, combined into a strain gage, a frequency converter of the signal from the output of the strain gage, containing a comparator and integrator, made the second capacitor is connected to the operational amplifier with the first capacitor in the negative feedback circuit, the output of which is connected to the first input of the comparator, between the output of which and the inverting input of the integrator operational amplifier, the inverting input of the integrator operational amplifier is connected through one resistor to the vertices of the measuring diagonal of the tensor bridge , and its other vertex is connected to the non-inverting input of the operational amplifier of the integrator and the second input of the comparator, a divider is introduced of two resistors, a second integrator resistor and an additional resistor, while the voltage divider is connected parallel to the diagonal of the sensor strain bridge power supply, the output of the voltage divider through the second integrator resistor is connected to the inverting input of the integrator operational amplifier, the first vertex of the tensi bridge power diagonal is connected through the additional resistor to the output of the comparator and the second peak is to the ground bus. In this case, an additional resistor is made of the same material as the strain gages of the strain gage of the sensor, is installed along the circuit behind the periphery of the membrane on its base or consists of two parts, the first of which is made of the same material as the strain gages of the strain gage of the sensor, is installed on the circuit for the periphery of the membrane at its base, and the second is made of resistive material and is located outside the membrane in the sensor or signal frequency converter.

A device for measuring pressure with a frequency output based on a nano- and microelectromechanical system (NIMEMS) contains a strain gauge pressure sensor 1 and a frequency converter 2 of the signal from the output of the strain gauge bridge.

The strain gauge pressure sensor 1 (Fig. 1) contains a housing 3 with a fitting 4 (Fig. 2), a thin-film nano- and microelectromechanical system (NIMEMS) 5 installed in it, output conductors 6, a cable jumper 7. The thin-film NIMEMS 5 is a structurally finished a module providing high adaptability of the sensor assembly.

The frequency Converter 2 (Fig.1) of the signal from the output of the strain gage can be made in the form of a microelectronic module 8 (Fig.2) installed in the sensor housing.

Figure 3 separately shows a thin-film nano- and microelectromechanical system (NIMEMS) of the pressure sensor 1. It consists of an elastic element - a round membrane 9, rigidly sealed along the contour, with a peripheral base 10 beyond the boundary 11 of the membrane, a heterogeneous structure 12, contact block 13 , the sealing sleeve 14, the connecting conductors 15, the output pegs 16, the dielectric bushings 17. A heterogeneous structure 12 of thin films of materials (thin-film dielectric, strain gauge, contact, etc. material layers) is formed ana the membrane 9 methods nano- and microelectronic technology in which are formed strain gages integrated in tenzomost.

Figure 4 presents a functional electrical diagram of a device for measuring pressure with a frequency output based on a nano- and microelectromechanical system (NIMEMS). It includes a strain gauge 18 of the strain gauge pressure sensor 1 (figure 2) and a frequency signal converter 2 (figure 2) from the output of the strain gauge bridge of the sensor.

The frequency Converter signal from the output of the strain gauge bridge 18 of the pressure sensor contains an integrator 19, made on the operational amplifier 20 with the first capacitor 21 in the feedback circuit, a comparator 22. The output of the operational amplifier 20 is connected to the first input of the comparator 22, between the output of which and the inverting input of the operational amplifier 20 the integrator 19 includes a second capacitor 23. The inverting input of the operational amplifier of the integrator 19 through the first resistor 24 is connected to one of the vertices of the measuring diagonal of the strain bridge 18, and its the corner vertex is connected to the non-inverting input of the operational amplifier 20 of the integrator 19 and the second input of the comparator 22. The voltage divider 25 of the resistors is connected in parallel with the diagonal of the power supply of the strain gauge bridge 18. The output of the voltage divider 25 through the second resistor 26 of the integrator 19 is connected to the inverting input of the operational amplifier 20 of the integrator 19. The first vertex of the power diagonal of the strain gauge bridge 18 is connected to the output of the comparator 22 through an additional resistor 27, and the second vertex is connected to the ground bus. An additional resistor 27 is made of the same material as the strain gages of the strain gauge bridge of the sensor, is installed beyond the periphery of the membrane along the circuit at its base. The additional resistor 27 may consist of two parts, the first of which is made of the same material as the strain gages of the strain gauge bridge, and is installed behind the periphery of the membrane along the circuit at its base, and the second is made of resistive material and is located outside the membrane in the pressure sensor 1 or frequency converter 2 of the signal from the output of the strain gauge bridge 18.

The thin-film heterogeneous structure 12 of the nano- and microelectromechanical system (NIMEMS) of the pressure sensor (Fig. 3) consists of nano- and micro-sized layers formed on a metal membrane 9 (36NKhTYu steel can be the material of the membrane) with a microroughness height of not more than 50-100 nm (with a membrane microroughness height of more than 100 nm, it becomes fundamentally impossible to obtain stable thin-film structures, and therefore new qualitative indicators characteristic of the sensor). It contains a dielectric layer (for example, in the form of a Cr-SiO-SiO ₂ structure, where Cr is used as a sublayer with a thickness of 150-300 nm), a resistive layer (for example, in the form of an X20H75Y structure, 40 ... 100 nm thick) and a contact group layer (for example, in the form of a V-Au structure for the formation of contact pads, jumpers, conductors). In a heterogeneous structure 12, photolithography and etching methods form a bridge circuit of circular 28 and radial 29 strain gages (Fig. 5) made in the form of identical strain gauge elements 31 (uniformly arranged along the membrane periphery) connected by low-resistance jumpers 30 (from the V-Au structure) (from the structure Х20Н75Ю, with a thickness of not more than 100 nm), an additional resistor 27 made of the same material as the strain gages of the strain gage of the sensor. An additional resistor 27 is formed on the base 10 beyond the boundary 11 of the membrane (Fig. 3) in an area insensitive to mechanical deformations from pressure.

A device for measuring pressure with a frequency output based on a nano- and microelectromechanical system (NIMEMS) works as follows.

The measured pressure P acts on the elastic element - the membrane of the strain gauge pressure sensor 1 (figure 1), the deformation of which with the help of strain gauges of the strain gage is converted to the voltage supplied to the input of the frequency Converter 2 (figure 4). At the output of the frequency converter 2 of the signal from the strain gage, a square wave signal of the meander type is generated with a frequency proportional to the measured pressure. The sensor is powered from a bipolar DC voltage source that does not require stabilization due to the fact that the strain gauge bridge 18 (Fig. 4) is supplied with voltage from the output of the frequency converter 2, the amplitude of which does not affect the frequency of the output signal of the device.

(где ε_R=ΔR/R - относительное изменение сопротивления тензомоста 18 под действием давления,

- коэффициент, равный отношению эквивалентного сопротивления параллельного соединения тензомоста 18, с сопротивлением R, и делителя напряжения 25, состоящего из двух резисторов с общим сопротивлением R_д=aR, к сопротивлению тензомоста 18) и отрицательным "скачком" через конденсатор 23, равным

, где С₂₃ - емкость конденсатора 23, C₂₁ - емкость конденсатора 21. Напряжение питания тензомоста U_cd при подключенном дополнительном резисторе 27 будет определяться выражениемIn the steady state of the device, the output of the comparator 22 of the Converter is followed by bipolar pulses of amplitude ± U ₀ . Let at the time t ₁ there was a change in the polarity of the output voltage from -U ₀ to + U ₀ . In this case, the voltage at the output of the integrator 19 is due to a positive "jump" in voltage from one of the vertices of the measuring diagonal of the tensile bridge 18, equal to

(where ε _R = ΔR / R is the relative change in the resistance of the strain bridge 18 under the action of pressure,

- a coefficient equal to the ratio of the equivalent resistance of the parallel connection of the strain gage 18, with resistance R, and the voltage divider 25, consisting of two resistors with a total resistance R _d = a R, to the resistance of the strain gage 18) and a negative "jump" through the capacitor 23, equal to

where C ₂₃ is the capacitance of the capacitor 23, C ₂₁ is the capacitance of the capacitor 21. The voltage supply of the strain bridge U _cd with the additional resistor 27 connected will be determined by the expression

- отношение сопротивлений дополнительного резистора 27 и тензомоста 18.Where

- the ratio of the resistances of the additional resistor 27 and the strain bridge 18.

Given the initial conditions, we have:

, и напряжения с выхода резистивного делителя напряжения 25, равного

, где ε_д=Δа/а - разбаланс делителя напряжения 25, напряжение на выходе интегратора 19 будет увеличиваться до положительного порогового уровня компаратора 22, равного

.Under the influence of the strain unbalance strain bridge 18, equal to

, and the voltage from the output of the resistive voltage divider 25, equal to

where ε _d = Δ a / a is the imbalance of the voltage divider 25, the voltage at the output of the integrator 19 will increase to a positive threshold level of the comparator 22, equal to

.

At the moment of equal response threshold and voltage at the output of the integrator, the polarity of the output voltage will again change.

In this case, the voltage at the output of the integrator will be equal to

wherein R ₂₄ and R _26, - respectively, the resistance of the first and second resistors of the integrator 19, C ₂₁ - capacitor 21 in the negative feedback loop of the integrator 19, T _k - oscillation period of the output signal.

For the moment of equal voltage at the output of the integrator and the threshold level of the comparator, the expression

Solving expression (6) relative to the pulse repetition period of the output signal T _to , we obtain the expression for the output frequency of the Converter

In the case when the first and second resistors of the integrator 19 are equal to R ₂₄ = R ₂₆ = R _and , expression (7) takes the form

In this case, the initial frequency of the output signal at zero imbalance (ε _R = 0) of the strain bridge 18 will be equal to

and frequency deviation depending on the measured pressure

Output Frequency Range converter according to a predetermined unbalance tenzomosta 18 which corresponds to a predetermined range of the measured pressure can be set via capacitance C of the capacitor ₂₃ and the resistance R _and the integrator, and an initial frequency - using the relationship ε divider resistors 25 voltage _d.

The introduction of an additional resistor 27 into the circuit reduces the supply voltage of the strain gauge bridge 18, reduces the power released by the strain gauges, and does not affect the sensitivity of the device, since the conversion function is independent of the supply voltage. Reducing the power released by the strain gauges, allows to reduce the heating temperature of the strain gauges from the current flowing through them. This reduces the power consumption of the pressure sensor 1.

Expressions (7) - (10) were obtained without taking into account the influence of the heating temperature of the strain gage and do not take into account the conversion error associated with a change in the resistances of the strain gages and the additional resistor 27.

Taking into account the influence of temperature for the output frequency of the converter, expression (7) takes the form

,

,

,

зависят от относительного изменения сопротивлений тензорезисторов, связанных с изменением температуры тензомоста и величиной температурного коэффициента сопротивления материала тензорезисторов.where are the values

,

,

,

depend on the relative change in the resistance of the strain gages associated with a change in the temperature of the strain gage and the value of the temperature coefficient of resistance of the material of the strain gages.

Mathematical modeling of the device, taking into account the real possible values of the circuit parameters and the specified ranges of the strain gage unbalance, the temperature of the pressure sensor heating, the frequency of the output signal, specific values of the temperature coefficient of resistance of the strain gages and an additional resistor, allowed us to obtain graphical dependences of the output signal on changes in the above parameters and make a comparative assessment of the claimed devices with a prototype.

Figure 6 shows the dependence of the output signal frequency on the strain gage imbalance ε _R according to expression (7) in the range from -0.01 to +0.01, without taking into account the influence of temperature, with the following circuit parameters: strain gage resistance R = 700 Ohm, resistance resistive voltage divider R = 140 kOhm ( a = 200), while the relative imbalance of the voltage divider ε _d = 0.04, the integrator resistance R ₂₄ = 27778 Ohms and R ₂₆ = 35714 Ohms, the capacitor capacitance is C ₂₃ = 40 pF in the absence of an additional resistor 27 (n = 0).

From the graph of Fig.6 it is seen that the dependence of the output signal frequency on the strain gage unbalance varies from 3000 Hz at ε _R = -0.01 to 11000 Hz at ε _R = + 0.01 and is equal to 7000 Hz at ε _R = 0, it is linear the character in the entire range of imbalance (both in the negative and in the positive region), which can be used in differential pressure sensors and, compared with the prototype [5], which works only with unilateral strain bridge imbalance, expands the functionality of the device.

When an additional resistor 27 is included in the device circuit with an increase in the ratio n = R ₂₇ / R (n = 1, n = 4), a decrease in the frequency of the output signal is compensated by an increase in the capacitance of the capacitor C ₂₃ .

Figure 7 shows the dependences at: n = 0, C ₂₃ = 40 pF; n = 1, C ₂₃ = 20 pF; n = 4, C ₂₃ = 10 pF; other parameters remained unchanged.

From the graph of Fig. 7 it is seen that with increasing n the linear nature of the dependence is preserved, but the slope changes somewhat. However, using the imbalance ε _{d of} the voltage divider, you can set the same initial frequency as for n = 0, and using the integrator resistors R ₂₄ and R _26, you can change the sensitivity or the range of the output frequency, and thereby change the slope of the direct frequency dependence .

When the temperature of the medium being measured increases, the strain gages are heated both by heating the sensor from the influence of the medium and by the flow of current through the strain gages, which limits the increase in the sensitivity of pressure sensors by increasing the voltage supply of the strain gage and, accordingly, increasing the signal amplitude from the output of the measuring diagonal of the strain gage due to limited power strain gages. With an increase in temperature and an increase in the imbalance of the strain gage, temperature changes in the resistance of the strain gages are affected, which lead to an additional conversion error.

On Fig shows the temperature dependence (11) of the output frequency of the Converter (figure 4) with a temperature change in the range from 0 to 150 ° C, taking into account the above temperature coefficient of resistance of the material of the strain gages in the absence of added resistor 27 (n = 0) and the imbalance of the strain bridge equal to ε _R = 0,01.

From the dependence graph (Fig. 8) it is seen that the frequency of the output signal decreases with increasing temperature and the relative temperature error for this case is 3%.

To reduce this error or to completely compensate for it by introducing an additional resistor 27 into the frequency converter circuit (Fig. 4). It should be noted that the magnitude and location of this resistor in the converter circuit affect the output signal frequency differently.

So, if an additional resistor is located directly in the microelectronic module 8 of the device (Fig. 2), assuming that its resistance does not change with increasing temperature, but only the resistance of the tensor bridge changes, then the frequency of the output signal of the device’s frequency converter will increase.

When an additional resistor is located on the membrane, it is made of the same material as the strain gages and placed along the contour beyond the periphery of the membrane at its base in an area insensitive to mechanical deformations from the influence of the measured pressure, at a heating temperature close to the temperature of the strain gages, the frequency of the output signal of the frequency converter of the device will decrease.

And finally, if you make an additional resistor in two-part, when one part is installed in the microelectronic module (as in the first case), and the other part is on the membrane (as in the second case), with various ratios, you can fully compensate for the temperature error transformations for certain ranges of temperature and measured pressure.

9-14, the relative change in resistances ε _{R is} denoted by the letter E.

Figures 9, 10 and 11 show the dependences of the frequency of the output signal on temperature in the range from 0 to + 150 ° C for n = 1 (R ₂₇ = R = 700 Ohm), strain gage imbalance (ε _R = 0; 0.005; 0, 01) and with various options for placing an additional resistor 27:

Option 1 - in the microelectronic module (in the circuit),

Option 2 - on the sensor membrane (on TM),

Option 3 - combined (comb.), When one part is installed in the microelectronic module, and the other part is on the membrane.

From the graphs (Figs. 9, 10, 11) it can be seen that when placing an additional resistor 27 in the microelectronic module (see - in the diagram), the frequency of the output signal increases with increasing temperature of the tensor bridge on the membrane, and when placing it on the membrane (see - on TM) it decreases. Full compensation of the temperature error of conversion, in which the frequency of the output signal remains unchanged for a specific range of unbalance of the strain gage, is carried out with the combined placement of an additional resistor (see. Comb.).

On Fig, 13, 14 shows a similar dependence of the frequency of the output signal at n = 4 (R ₂₇ = 4R = 2800 Ohms).

It should be noted that in order to completely compensate for the temperature error in the case of combined placement of an additional resistor (comb.) With an increase in its value, the ratio of the parts placed on the membrane and in the microelectronic module of the converter (R _tm / R _cx ) should be changed. Moreover, the greater the value of n, the greater its component should be on the membrane in the area of the tensor bridge (TM). So, for example, with an imbalance ε _R = 0.005 for n = 1, this ratio will be 0.551, and for u = 4 it will be 0.717, i.e. a smaller part of the additional resistor should be located in the microelectronic module, and a large part - on the membrane.

On Fig shows the dependence of the ratio of the parts of the additional resistor R ₂₇ , in which the temperature error is compensated, on the unbalance range of the strain gage (ε _R = 0; 0.005; 0.01) and the value n = R ₂₇ / R (1; 4; 10 ), where R _tm is the part of the resistor located on the membrane, R _cx is on the microelectronic module (circuit). Moreover, R ₂₇ = R _tm + R _cx .

Thus, for given values of the range of measured pressures, the temperature of the heating of the strain gage, the frequency range of the output signal of the device, by correctly selecting the parameters of the circuit elements of the frequency converter of the signal from the output of the strain gage, it is possible to significantly reduce (or completely compensate) the measurement error of the device associated with a change in the temperature of the measured medium and with heating the strain gauge of the pressure sensor.

The circuit diagram of the electrical device was modeled using the computer program "Micro-Cap" and is presented in Fig.16. On Fig shows the waveforms and amplitudes of the signals from the output of the comparator device (upper diagram) and from the output of the integrator (lower diagram), as well as the frequency of the output signal (in the upper right corner). The results of circuit computer simulation confirmed the validity of the derived expressions and the results of mathematical modeling.

Information sources

1. Vasiliev V.A. Technological features of solid-state membrane sensitive elements. // Bulletin of Moscow State Technical University. Ser. Instrument making. - M., 2002 - No. 4. - S.97-108.

2. Belozubov EM RF patent No. 2031355, 6G01B 7/16. Strain bridge thermal compensation method. Bull. No. 8 dated 03/20/95.

3. Belozubov EM RF patent No. 1615578 5G01L 9/04. Pressure meter. Publ. 12/23/90. Bull. No. 47.

4. Belozubov EM, Belozubova N.E. Thin-film strain gauge pressure sensors are products of nano- and microsystem technology. // Nano- and microsystem technology - M., 2007. - No. 12. - S. 49-51.

5. Gromkov N.V., Mikhotin V.D., Shakhov E.K., Shlyandin V.M. A.S. USSR No. 828406, M. Cl. H03K 13/20. Publ. 05/07/81. Bull. Number 17.

Claims (3)

1. A device for measuring pressure with a frequency output based on a nano- and microelectromechanical system (NiMEMS), comprising a strain gauge sensor consisting of a housing, a NiMEMS installed in it with an elastic element in the form of a membrane with a base formed on it by a heterogeneous structure of thin films of materials in which strain gages are integrated in a strain gage, a frequency converter of the signal from the output of the strain gage, comprising a comparator and an integrator made on an operational amplifier with a first condensate ohm in the negative feedback circuit, the output of which is connected to the first input of the comparator, between the output of which and the inverting input of the integrator’s operational amplifier, a second capacitor is connected, the inverting input of the integrator’s operational amplifier is connected through one resistor to the vertices of the measuring bridge diagonal, and its other vertex is connected to the non-inverting input of the operational amplifier of the integrator and the second input of the comparator, characterized in that a voltage divider of two resistors is introduced, in an integrator resistor and an additional resistor, while the voltage divider is connected parallel to the diagonal of the sensor strain bridge power supply, the output of the voltage divider through the second integrator resistor is connected to the inverting input of the integrator operational amplifier, the first vertex of the strain bridge power diagonal is connected to the comparator output through the additional resistor, and the second vertex to the ground bus. 2. The device according to claim 1, characterized in that the additional resistor is made of the same material as the strain gages of the strain gauge bridge of the sensor, is installed along the contour beyond the periphery of the membrane at its base. 3. The device according to claim 1, characterized in that the additional resistor consists of two parts, the first of which is made of the same material as the strain gages of the strain gauge bridge of the sensor, is installed along the contour behind the periphery of the membrane at its base, and the second is made of resistive material and located outside the membrane in the sensor or inverter of the signal.

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