RU2603446C1 - Device for pressure and temperature measuring - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: invention relates to measurement equipment and can be used for simultaneous measurement of pressure, temperature and heat flow with compensation for temperature influence on pressure measurement results. Sensitive element (SE) for pressure measurement is selected "silicon-on-sapphire" consisting of artificial sapphire and titanium metal film. In addition to sapphire substrate lower plate is included, and upper plate is capacitor titanium film. On sapphire four armed strain-gauge bridge (TM) is formed. Capacitive SE is formed by arrangement of dielectric ring between capacitor lower and upper plates and is protected from external electromagnetic noise with shield. Temperature and heat flow SE is coaxially and symmetrically formed on upper and lower surfaces of other dielectric film. Sensor structure package consisting of two parts is assembled under vacuum, located inside housing and protected by mesh. For electric connections provision is made for terminal block with connectors and circuit board, on which high-resistance protective circuit and charge amplifier are mounted. Sensor cavity behind membrane maintains communication with atmosphere by pipe with covers, passing through sensor structure first part. On sensor structure second part at least 10 support through holes are made. Between sensor structure first and second parts air gap is formed. Communication with atmosphere between sensor structure first and second parts is accomplished by support pipes and holes. Sensor housing is connected to device common ground and sensor structure first part and filled with soft sealant.

EFFECT: technical result consists in possibility of simultaneous measuring in specified section of sound pressure (pulsations, explosive, impact, wind), sound pressure (total pressure), static pressure (absolute, excess, differential), temperature and heat flow.

1 cl, 2 dwg

Description

The invention relates to measuring technique and can be used to measure total pressure (sound pressure), sound pressure, static pressure, temperature, heat flux, etc. in aviation technology, mechanical engineering, shipbuilding, oil and gas industry.

A known pressure sensor containing a capacitive sensitive element (ECE) and a strain gauge bridge (TM). ECE contains a base of a dielectric film and a main screen. On the upper surface of the base are electrical connectors, a metallized bottom plate of the capacitor. The sensor cavity is connected with the atmosphere by a capillary hole with a diameter d. The sensor membrane (upper plate) of a cylindrical shape is formed in vacuum from dispersion precision alloys or from various high-quality alloys and from a semiconductor. Resistance r ₁ , r ₂ , r ₃ , r _{4 are} electrically isolated from the surface of the sensor by a dielectric film. The membrane is connected to the base, the side screen with thin wires through a capillary hole with one of the connectors. The shape of the membrane can be flat with perforated cells: a small serrated, sinusoidal, toroidal profile of the corrugation. On the effective surface of the membrane in vacuum, a four-arm tensor bridge (TM) with the diagonals a, b; c, d and active resistance of the shoulders r ₁ , r ₂ , r ₃ , r ₄ . To measure the pressure from the TM output, low-frequency equipment (ANF) was used. Diagonals a, b TM are connected to a power source. The output of the ECE sensor (through one of the connectors) through the charge, voltage (UN) amplifiers is connected to the input of the subtraction unit and indicator. The other diagonals TM in and g across the arm of the ANF are connected to the input of the subtraction block. Moreover, the capacitive sensor is polarized by a separate power source.

Such sensitive elements (SE) of the pressure sensor allow you to measure sound pressure, sound pressure, static pressure, etc. on the studied object by the method of draining the surface of the products [1 - RF patent No. 2267757, G01L 9/12, G01L 9/08 "Sensor and method of measuring pressure", authors A.A. Ghazaryan, A.A. Cooks].

The sensor has the following disadvantages: The pressure sensor SE is not protected from external influences. In particular, it is poorly protected from external electromagnetic interference. Lack of information about the temperature, the ability to assess the effect of temperature on the measurement results.

The closest technical solution to the proposed invention is a sensor for measuring pressure. The sensor for measuring pressure contains: a base made of a dielectric film, a main screen formed on its surface, a capacitor plate, a membrane of a flat shape or with a corrugated, toroidal profile. In this case, the internal cavity of the sensor is connected to the atmosphere through a capillary hole. A TM is formed on the membrane surface, electrically isolated from the membrane surface by a layer of a dielectric film. The sensor is equipped with low-frequency equipment (ANF), a DC power source, a charge amplifier (US) and voltage (UN), a subtraction unit, and an indicator. One of the TM diagonals is connected to a power source, and the second TM diagonal is connected through an ANF to the indicator and to the input of the subtraction unit, which is connected to the indicator. The capacitive output of the sensor through the connector, US and UN is connected to the input of the subtraction unit and indicator. Strain gauge sensitive elements (SE) TM and capacitive elements of the capacitor are made on the basis of "silicon on sapphire." ECHE and TM are protected by a protective grid, contain a terminal block with connectors, a support tube with a cover, a body filled with soft sealant, two resistors and a capacitor. The upper lining of the ECE sensor through the cable screen is connected to the positive pole of the ultrasound. Both resistors and the second capacitor are connected at one point. The first resistor is connected to the core cable, with the first capacitor and the bottom plate of the ECE sensor. The second resistor is connected to the positive pole of the polarization source. The negative pole of the polarization source is connected to an external shield and local ground. ECHE and TM are connected at the same output of the DC source and supply the pressure sensor with the same voltage. The subtraction unit is located inside the sensor housing.

Such SE pressure sensors allow you to measure sound pressure, sound pressure, static pressure, etc. at the test object by the method of drainage of products [2 - RF patent No. 2384825, G01 L / 12 "Sensors for measuring pressure", authors A.A. Ghazaryan, V.V. Petronevich, N.A. Ezeev]. The sensor has the following disadvantages: CE sensors do not provide the conversion of pressure into an electrical signal, regardless of temperature. There is no information on the effect of temperature on the sensor.

The objective of the present invention is to expand the scope, increasing reliability. The technical result is achieved through the development of a compact sensor design based on TM, ECE and CHET. The strain gauge bridge is designed on the basis of a single crystal structure "silicon on sapphire" and is formed in a monolithic manner.

The technical result is achieved in that in a pressure sensor containing a base of a dielectric film, a main screen formed on its surface, a capacitor lining, a membrane with an edge, for example, a toroidal profile of a flat shape or with a corrugated profile, assembled in a bag, connectors that connect the lining, a membrane, a main screen, a strain gauge bridge with an external circuit, while the internal cavity of the sensor is connected to the atmosphere through a capillary hole, a strain gauge bridge is formed on the surface of the membrane, electrically isolated from the surface of the membrane by a layer of dielectric film, strain gauge and capacitive sensitive elements of the sensor based on "silicon on sapphire", a protective grid, a terminal block with connectors, a support tube with a cover, a body filled with soft sealant, two resistors and a capacitor, the top one the lining of the capacitive sensor element through the cable screen is connected to the positive pole of the charge amplifier, both resistors and the second capacitor are connected at one point, the first resistor is connected with a residential cable, with the first capacitor and the lower lining of the capacitive sensor element of the sensor, the negative pole of the polarization source is connected to an external screen and local ground, and the sensor is equipped with low-frequency equipment, a DC power supply, a charge and voltage amplifier, a subtraction unit, an indicator, and the capacitive sensor element and the strain gauge bridge are connected at one output of the direct current source and supply the pressure sensor with one voltage, and the subtraction unit is located inside three sensor housings, two hot junction temperature sensing elements are additionally introduced, symmetrically located between each other on the upper and lower surfaces of the dielectric film, two cold junction temperature sensing elements, cold junction thermocouples are located outside the device housing, provide the ice melting temperature, are interconnected and through the switch is connected to the indicator, a metal ring, two potentiometric amplifiers, memory blocks, one switch, three subtraction blocks, and m in the first position of the switch, the output of the low-frequency equipment, the voltage amplifier through the switch, memory blocks, subtraction units are connected to the indicator inputs, in the second position of the switch, the outputs of the low-frequency equipment and the voltage amplifier through the switch are connected to the inputs of three subtraction units and their outputs are connected to the input indicator, the outputs of two temperature sensors through potentiometric amplifiers and a subtraction unit are connected to the indicator, the output of one of the potentiometric of amplifiers is connected to the indicator, the output of another potentiometric amplifier is also connected to the indicator through memory blocks, with the charge amplifier mounted inside the sensor housing on the bottom surface of the circuit board, the sensor housing connected to a common bus at point B of the device, on the second part of the sensor construction, consisting of two dielectric films and temperature sensitive elements, at least ten through support holes are made through them, the cavity of the capacitive sensitive element behind the membrane is connected and with the atmosphere through a support tube passing through the first part of the sensor structure, consisting of a mounting plate, an air gap, a multi-pin connector, a screen on the surface of the dielectric film and a casting compound, the air gap being formed between the first and second parts of the sensor structure, and between the first and the second part of the sensor design is a metal ring.

In FIG. 1 shows the construction of the pressure sensor assembly and FIG. 2 is a block diagram of a pressure and temperature measuring device.

In FIG. 1, the first part of the device’s construction contains a dielectric film 1, on the bottom surface it contains filled sealant 2, on the top there is a screen 3, block 4, a mounting plate 5, on the bottom surface there is an electric circuit of the charge amplifier 6, and on the top there is a protective circuit 6 ′, consisting of resistors R ₁ , R ₂ and capacitors C ₁ , C ₂ (Fig. 2), and a metal ring 7. The second part contains a base of a dielectric film 8, on the upper and lower surfaces respectively CHET 9, 10 (temperature sensitive elements hot thermocouples about junction), BET of cold junction 9 ′, 10 ′ (which are not located inside the device case), dielectric film 11, the lower lining of the capacitor 12 is formed on the upper surface, rings 14 are located between the lower 12 and the upper 13 lining, represents the ECHE 15; on the top cover 13, i.e. on the surface of the membrane, an insulating film 16 of any dielectric, in particular of artificial sapphire, is located. On the surface of the dielectric film 16 is TM 17 (Fig. 1 section. A-A). More than 10 support holes 18 are formed through films 8-12. The support holes with the atmosphere are connected by a support tube 19 with an inner diameter d = 0.1-0.35 mm (Fig. 1, section A-A, B-B). A cover 20 is put on the end of the support tube 19. All nodes from 1 to 19 positions, assembled in a package, are placed inside the housing 21 with the exception of the CHET cold junction. The housing 21 is equipped externally with a hexagonal protrusion 22 for mounting the sensor on the test object (IO). On the lower surface of the metal ring of the sensor is located below the first part of the sensor structure, and on the upper surface is the second part of the sensor structure. TM 17 from external influences is protected by a mesh 23. The support tube 19 passes through the film 1-5 of the first part of the sensor structure. Between films 5 and 8, i.e. between the first and second parts of the sensor design, an air gap is formed 24. The cavity 25 behind the membrane 13 of the ECE 15 is connected by numerous support holes 18 (Fig. 1, section A-A, BB). For reliable signal pick-up from the outputs of TM 17 and ECHE 15, a special block 4 is provided, the block is equipped with connectors or pressure outputs. The forming harness 26 (bundle of wires), including a common bus, is connected to the housing of the sensor 21 at point B, goes outside for connection with an external circuit. UZ 6, protective circuits 6 ′ are located inside the sensor housing 21. This design solution increases the reliability of the sensor by reducing the distance between the ECE 15 and the high-impedance input of UZ 6, protects against external electromagnetic interference.

The symmetrical arrangement of the support holes 18 (Fig. 1 sec. BB) behind the membrane of the internal cavity 25 ECE 15 (Fig. 1 sec. A-A) provides uniform deflection of the membrane. Equalization of the static pressure behind the membrane is necessary to achieve the most accurate determination of the lower range of the operating frequency. The presence of an air layer, depending on the operating conditions of the membrane, allows introducing additional attenuation or additional elasticity into the membrane operating mode. The presence of support holes when changing sound frequency in a wide range, the influence of inertia of air, the influence of internal friction of the membrane, etc. equally and slightly change the acoustic impedance of the ECE. It is known that the sensitivity of an ECE with a small air cavity 25 between the upper 13 and lower 12 plates (Fig. 1, section A-A) does not depend on the thickness of the ring 14 if the external shunt capacitance is negligible compared to the capacity of the ECE. This leads to the cancellation of the effect of increasing the stiffness of the air cushion when the gap decreases and vice versa. The support holes behind the membrane improve the sensitivity of the ECE by a factor of twenty [3 - RF patent No. 2334964 G01L 9/12. 2008].

The pressure and temperature measurement block diagram of FIG. 2 contains TM 17 with diagonals a, b (first shoulder), c, d (second shoulder) with active resistances r ₁ , r ₂ , r ₃ , r ₄ . Used equipment low frequency 27 (ANCH). Diagonals a, b TM are connected to a power source (IP) 28, which polarizes an ECH, consisting of a bottom plate 13, located in the design of an ECHE pressure sensor 15. The output of an ECH sensor through a capacitor C 2, UZ 6, UN 29, the first switch position 30 , the subtraction blocks 32, 33 are connected to the inputs of the indicator 34. Other diagonals TM v, d through the ANF 27, the first position of the switch 30, the memory blocks 35, 31, the subtraction blocks 36, 33 are connected to the input of the indicator 34. In the second position of the block 30, the outputs ANCH 27, UN 29 through switch 30, subtraction blocks 36, 32, respectively Connect the indicator to. In this case, the outputs of the ANCH and UN through the block 30 are connected to the input of the indicator. The outputs of the subtraction blocks 36, 32 through the subtraction block 33 are connected to the input of the indicator. Other outputs of block 36, 32 are also connected to the indicator input. At the same time, CHET 9, 10 are simultaneously connected via potentiometric amplifiers (PU) 37, 38 and through subtraction block 39 to the inputs of indicator 34. The other two outputs of PU 38 are connected to memory blocks 31, 35. The input of switch 30 is also connected to the indicator. The second TM diagonal at point b is connected to a common bus (wire) at point B.

The polarization of the ECE and the power supply of UZ 6 and UN 29 are performed by IP 28.

The input of the sensor are layers of metal 13, dielectric films 16 and TM 17, which are supplied with pressure. Selected wires 26 of the AVKT-6 brand are used in operating conditions with increased radiation, vibration, and temperature. The bottom plate 12 ECE through the core of the cable and the first capacitor C2 is connected to the negative pole of the ultrasound. Screen 3 (Fig. 2) is connected to the screen of the anti-vibration cable and at point B of the local ground. The positive pole of the UZ 6 is the common bus device. Screen 3, the negative pole of the polarization source 28, the upper plate 13 through the screen of the cable are connected to the common bus of the device at point B (positive pole). The second capacitor C1, the resistors R1 and R2 are interconnected in series, and the free end R1 is connected to the first capacitor C2. The other end of the resistor R2 is connected to the positive pole of the polarization source 28. The negative pole of the polarization source is connected to the positive pole of the ultrasound 6. Intermediate junctions of the plates A, B and A ′, B ′ are formed at the places where the BET 9, 10 and 9 ′, 10 ′ are connected lead wires C, D and C ′, D ′ of FIG. 2. CHET 9 ′, 10 ′ through the electronic switch 30 ′ is connected by wires C, D to the indicator. The connection of CHET 9, 10 and 9 ′, 10 ′ is carried out among themselves through the switch 30 ′ or separately under the indicator command. The low temperature of the (cold) junction CHET 9 ′, 10 ′ is ensured by placing it in the environment of melting ice or something else. CHET 9, 10 and 9 ′, 10 ′ consist of two different conductive plates A, B and A ′, B ′, for example, copper and nickel, and this place is subjected to heating or cooling. The lead wires C, D connect the blocks 37, 38 to the cold junctions A ′ and B ′ with the wires C ′, D ′ and thermocouples 9 ′, 10 ′ are connected to the indicator.

The main requirements that apply to the storage device in the indicator are: the ability to store information for a long time with the possibility of continuous and non-destructive reading; ability to quickly record new information on indicator signals. Forms of information in the form of long pulses subject to long storage. Subtraction blocks containing several input and output resistors provide the subtraction of voltages connected to them. An operational amplifier (OA) is connected at the output of the resistance, and a voltage close to zero is maintained at the OA input. The op-amp provides amplification of both direct voltage of positive and negative polarity, and alternating voltage. Potentiometric amplifiers are direct current amplifiers. In them, when the emitter potential is increased, the next stage is achieved by passing through its emitter resistance in the form of a semiconductor zener diode. Among the main requirements is the indicator control system, which provides switching of external units (UN, ANCH, PU, subtraction blocks, etc.) with indicator blocks, sets the solution time, synchronizes the operation of individual blocks, selects and connects measuring units in the device. The indicator also provides input and output of information consisting of a switching system designed to connect individual indoor units to each other in accordance with a given program (usually in the form of a switching or typesetting field); means for setting the transmission coefficients of the initial values of the variables; systems for outputting and recording results, etc.

The ECE sensor has a high output impedance and, when polarized, in particular, with a DC voltage at the output, has an electric signal with a power of ~ 10 ^-13 -10 ^-15 W. Such a signal is cabled through a matching circuit, i.e. Ultrasound can be transmitted over long distances (50 m or more). One of the possible options for matching circuits is ultrasound. UZ provides a high input impedance with a closed input. The amplifier located next to the ECH in the sensor housing 21 is not sensitive to interference and interference caused by cable oscillation. The ultrasound was developed on the basis of an operational amplifier with deep negative feedback (“Device for measuring sound pressure”, RF patent No. 2281470, 2006, bull. No. 22, authors A. A. Kazaryan, L. M. Moskalik).

. При воздействии давления сопротивление ТМ можно представить состоящим из переменной и постоянной составляющих:

, где

, а r₀ - начальное сопротивление ТМ. Если все сопротивления моста равны, ТМ при Δr=0 уравновешен. В принципе ТМ можно выполнять с двумя активными, одинаково изменяющимися сопротивлениями, т.е. имеем полумост. Полумост характерен тем, что r₁=-r₂, r₃=-r₄, как Δl=Δl₁=-Δl₂, Δl₃=-Δl₄=0. При этом напряжение U_п и U_вых взаимно связано как:

. Полный ТМ с четырьмя активными, одинаково изменяющимися сопротивлениями характеризуется тем, что r₁=r₃=-r₂=-r_4, при этом имеем удлинение и укорочение сопротивлений, т.е. Δl₁=Δl₃=(растяжение)=-Δl₂=-Δl₄ (сжатие).In order to obtain an electrical signal at the TM output, proportional to the resistance changing under the influence of pressure, to them, i.e. To these resistances r ₁ , r ₂ , r ₃ , r _{4, an} electrical voltage U _p from IP 28 should be supplied. In principle, a TM can be powered with either constant or alternating voltage. A TM powered by DC voltage and made using metal or semiconductor strain gages does not require phase balancing. If TM is not balanced output TM (wherein ANCh 27 connected in the diagonals, and d) the bridge is not in an equilibrium state, a voltage at the output U _O ANCh. Between the output voltage and power there is a known relationship:

. When exposed to pressure, the resistance of the TM can be represented as consisting of a variable and a constant component:

where

, and r ₀ is the initial resistance of the TM. If all the bridge resistances are equal, the TM at Δr = 0 is balanced. In principle, TM can be performed with two active, equally changing resistances, i.e. we have a half bridge. The half-bridge is characteristic in that r ₁ = -r ₂ , r ₃ = -r ₄ , as Δl = Δl ₁ = -Δl ₂ , Δl ₃ = -Δl ₄ = 0. The voltage U _n and U _O mutually related as:

. A complete TM with four active, equally changing resistances is characterized by the fact that r ₁ = r ₃ = -r ₂ = -r _4, while we have an elongation and shortening of the resistances, i.e. Δl ₁ = Δl ₃ = (tension) = - Δl ₂ = -Δl ₄ (compression).

The voltage on the diagonals (output) of the bridge in, r increases as:

, откуда из начальных условий следует, что ε₁=-ε₂=ε₃=-ε₄=ε, при этом имеем

.The relationship between the output voltage and the TM is more obvious when this dependence is linear, and the pressure P acting on the TM is zero. In addition, changes in each of the bridge resistances have a certain orientation so that there is no mutual compensation of the TM output signal. In FIG. 2 TM included so that the resistance r ₁ , r ₂ , r ₃ , r ₄ cause a positive increment of the output voltage, has the form

, whence it follows from the initial conditions that ε ₁ = -ε ₂ = ε ₃ = -ε ₄ = ε, and we have

.

, а для четверти моста

. Величина коэффициента k=100-150, с его помощью можно регулировать нелинейность ТМ.According to the last expression, we can write that the output voltage of the half-bridge is in the ratio

, and for a quarter of the bridge

. The coefficient k = 100-150, with its help it is possible to adjust the nonlinearity of the TM.

The proposed sensors are based on the well-known highly reliable Sapphire 22 semiconductor sensor, primarily due to the direct conversion of the membrane and TM deformation into electrical output signals from the outputs of the ECHE and TM based on the silicon-on-sapphire single crystal structure. Hybrid microelectronics and compact all-welded design of TM sensors provide high reliability and stability of metrological characteristics in various operating conditions.

To create and develop new energy-saving, environmentally friendly "nano" technologies of production processes, research, scientific experiments in aerospace engineering, mechanical engineering, energy, petrochemical industry and to increase the accuracy of measurement and reduce the cost of the work, the proposed sensor is extremely necessary.

The solution to these problems was greatly facilitated by the work on the modernization of the Sapphire-22 strain gauge sensor complex carried out by specialists of the Research Institute of Thermal Appliance and MPO Manometer [Pressure Sensors. "Devices and control systems" No. 11, 1990, art. 27-30, ed. G.G. Jordan, A.Ya. Yurovsky and others.]

In the design of the pressure sensor, a modernized multilayer sandwich based on "silicon on sapphire" is used as a TM and ECE. This allows you to cover a very wide range of measured pressures. The upper limits of measurements of various modernized models are in the pressure range from ± 0.03 kPa to 1000 MPa. The tensoresistive effect is used in a heteroepitaxial silicon film grown on the surface of a single crystal substrate on artificial sapphire.

For reliable connection of thin-walled ТМ (0.15-0.2 mm) with leads, connectors, high-temperature soldering in vacuum is applied. The high mechanical strength of the single-crystal sapphire substrate and the good elastic properties of, for example, a titanium membrane make it possible to ensure a high level of TM working strains, make it possible to change the output signal at the TM output 300-400 mV in proportion to the change in the input value when the TM is supplied with a stabilized constant voltage. ТМ “silicon on sapphire” is also equipped with a unit for compensation of additional errors that occur, for example, when changes in temperature and / or static pressure of a controlled environment, ambient temperature, supply voltage, humidity. The compensation unit is part of the resistances r ₁ , r ₂ , r ₃ , r ₄ in the TM and is located on the surface of the sapphire dielectric film. To measure ultrahigh pressures (160-1000 MPa), the ECE membrane is made (manufactured) with a corrugated profile with cells of a small serrated profile of a corrugation, with a corrugated profile with cells of a deep serrated profile of a corrugation, with a corrugated profile with cells of a trapezoidal profile of a corrugation, with a corrugated profile with cells sinusoidal profile of the corrugation.

The advantages of single-crystal sapphire are that it does not have hysteresis and fatigue phenomena inherent in the metal, as well as thermal deformations arising due to the difference in temperature expansion coefficients of sapphire and metal (titanium) when the TM is connected to the metal case of the sensor and leading to additional temperature errors .

For the manufacture of a sapphire membrane for different ranges of pressure measurement, the developed methods of plasma-chemical etching of sapphire are known, which can be carried out at temperatures not exceeding 700 ° C. Sapphire etching occurs as a result of its interaction with the free radicals of atomic fluorine. The etching rate of sapphire is significantly dependent on temperature and is associated with the uniformity of etching of the ECE membrane of large sizes. On the surface of the ECE membrane, the resistances r ₁ , r ₂ , r ₃ , r _{4 of the} TM are located from the edge on the surface of the sapphire dielectric film, which will allow the TM to work under conditions of purely elastic deformation. This provides an increase in the linear dependence of the _Uoutput TM output voltage on the action of pressure. In TM, r ₁ -r ₄ strain gages can be made of silicon with p-type conductivity with crystallographic orientation (001).

The metal nodes of the pressure sensor, the support tube 19 with a cover 20, the housing 21 with a hexagonal protrusion 22, a protective mesh 23 are made of various corrosion-resistant materials. For example, the case and protective mesh are made of 29NK alloy (Kovar) or 12Kh18N10T steel. Overall dimensions of the sensor: length L = 25-35 mm, diameter D = 11-12 mm. Support tube 1 × 0.25; from steel 12X18H10T standard tube. The connector is made of a dielectric, depending on the pressure measurement conditions in the temperature range from -50 to + 80 ° C, for example, from a B-10 ebonite rod, the connector rods are made from MT-0.4 wire. Soft casting compound 14 low-viscous elastic for hardening, sealing and isolation of electric circuits of the ELK-12 brand, operable under high vibration and shock loads in the temperature range from -60 to + 120 ° С. If necessary, connections to ELK-12 can be dismantled.

The used ANF is known in measurement technology in 4 and 8 channel versions at the carrier frequency. Four- and eight-channel ANFs are designed to amplify signals from the TM when measuring the total pressure (sound pressure) and static pressure of the object under study. Coordination of the electrical signal from the output of the capacitive sensor is carried out by ultrasound, then amplified, normalized to the UN and fed to the indicator. Coordination and amplification of the electrical signal from the output of the capacitive sensor can be carried out by Bruhl & Kjерr equipment (Denmark), RION (Japan), RFT (Germany). Experience in measuring pressure has shown that pressure sensors can be connected to foreign equipment without the use of an additional matching circuit. In some cases, you have to choose the counterpart of the sensor connector. Domestic charge amplifiers are made on an integrated microcircuit 544UD1. To measure sound pressure also use the equipment "CHARGE", UZ RSh2731 / 4. The electrical capacitance of sensors from 3 pF and above (almost without restrictions) is consistent with the input of the charge amplifier. The output voltage is 5 V, 10 V. The equipment output is designed to work with analog-to-digital converters, oscilloscopes, magnetic drives, etc. In the ANF, a DC amplifier (UPT) is used to coordinate the TM with an external electric circuit, then the output of the UPT is coordinated with the input of the low-frequency amplifier. The input stage UPT is made according to the differential circuit.

The ECH of the sensor from external electromagnetic influences is protected by a housing, grid, screen by connecting the shields of the AVKT-6 wires with the main screen 3 and local grounding at point B. The introduction of additional elements in the device (sensor) allows isolating the ECH sensor capacitance from the cable capacity by introducing a circuit resistors R1, R2, the second capacitor C1 and compensate for the cable capacity. In the case when the ultrasound is not located inside the sensor housing near the ECH, this allows to increase the distance between the sensor and the charge amplifier in (in particular, up to 50 m). The cable length between the sensor and the ultrasound is limited only by the conductivity of the cable and the frequency properties of the ECE. The selected resistors R1, R2 are the same in value. The reliability of the sensor is increased by placing ultrasound in the sensor housing and due to the protection of the ultrasound from the polarization voltage entering its input. The first capacitor C2 is connected between the ECE and the ultrasound. Reliability is also improved by measuring the useful signal and applying the supply voltage of the TM and polarization of the ECH sensor with one cable (wire).

The four-arm TM is made with different resistances from r = 30-400 Ohms; r = 100-400 ohms; r = 200-400 ohms. In this case, the voltage at the output of the ANF U _out = ± 5 V (with a load resistance of 160-170 Ohms). A TM developed on the basis of "silicon on sapphire" is supplied with a DC voltage of 36 V or 15-42 V. At the same time, these voltages are the polarization voltage of the ECH. The dielectric film 8 contains BET 9, 10 to determine the temperature and heat flux. A thermocouple of two metals, nickel (lower) and copper (upper), is applied to the lower surface of layer 8. The signals taken correspond to the temperature at the junction of two metals. The equipment of the film 8 (Fig. 1 cross-section A-A) with thermocouples 9, 10 and their arrangement symmetrically with respect to each other allow the formation of a heat flow SE. The maximum possible thermoelectric effect is possessed by metal layers, which can be deposited by evaporation in vacuum. Nickel and copper satisfy this requirement. To equalize their ohmic resistances, the area of the nickel plates (lower ones) is 1.4–1.6 times the area of the copper plates. The choice of a ratio outside the specified limits complicates the coordination of the BET 9, 10 with PU 37, 38, in particular, when balancing resistors, PU 37, 38. The limits are characterized by temperature coefficients of two metals (α _Cu = 0.0045 and α _Ni = 0.0068) . The thickness of the BET is 0.18-0.2 microns, sizes 1 × 1 mm or diameters from 1 mm to 4 mm.

Thus, it is assumed that the proposed device allows at a given point in the IO one sensor, consisting of TM, ECHE and BET, simultaneously with the measurement of sound pressure to measure sound pressure, static pressure, temperature, heat flux. At the same time, at the output of the TM and ECE we have information about the measurement of pressure without the influence of temperature on the measurement results.

The device operates as follows.

The sensor is placed on a specific section of the IO and the pressure is not set on it (it is isolated from pressure) P = 0 and the temperature is set from 20 to 100 ° C.

передают через I-е положение переключателя 30 блока памяти 31, 35 и индикатор для запоминания и хранения. Напряжение с выхода ПУ 38 подают на входы блоков памяти 31, 35. С выхода ПУ 37 сигнал U_θ подают на индикатор. На выходе УН регистрируют

. На датчик задают в первом положении стандартное калибровочное звуковое давление Р≠0 и температуру. В этом случае с выхода АНЧ регистрируют сигнал U_выхθ и на выходе УН -

, сигналы с U_выхθ,

с выходов АНЧ, УН через II-е положение блока 30 подают на входы блоков вычитания 32, 36, где после операции вычитания полезные выходные сигналы АНЧ и УН - на входы индикатора и блока вычитания 33, т.е. измеряют основной сигнал. Оба сигнала регистрируют в индикаторе, затем определяют коэффициенты преобразования измерительных каналов, т.е. определяют значение последних сигналов с выхода АНЧ ΔU_вых=U_выхθ-U_0θ; с выхода

; при этом коэффициенты преобразования каналов определяют как:At the same time, from the output of the ANF and UN on the indicator, the sum of the signals of the internal noise of the equipment and thermal noise are recorded, i.e. measure zero signals. At the output of the ANF, an electrical signal U _{0θ is recorded} . Simultaneously with the PU output, U _{θ is} recorded, i.e. electrical signal proportional to thermal noise. Simultaneously with the output of the ANF and UN signals U _0θ and

transmit through the I-th position of the switch 30 of the memory unit 31, 35 and an indicator for storing and storage. The voltage from the output of the PU 38 is fed to the inputs of the memory blocks 31, 35. From the output of the PU 37, the signal U _{θ is} supplied to the indicator. At the output of the UN register

. In the first position, the standard calibration sound pressure P за 0 and temperature are set on the sensor. In this case, from the output of the ANF register the signal U _o

, signals from U _o

from the outputs of the ANCH, UN through the II-th position of the block 30 is fed to the inputs of the subtraction blocks 32, 36, where after the subtraction operation the useful output signals of the ANCh and the UN are fed to the inputs of the indicator and the subtraction block 33, i.e. measure the main signal. Both signals are recorded in the indicator, then the conversion coefficients of the measuring channels are determined, i.e. determine the value of the last signals from the output of the ANF ΔU _out = U _outθ -U _0θ ; from exit

; wherein the channel conversion coefficients are defined as:

, где P(t), Р₁, B_k и C_k имеют размерность измерения давления, их определение известно в измерительной технике, ω - угловая частота.Per sensor, i.e. the sound pressure (in the second position of the switch), with a non-periodic function of time in the form of the Fourier integral, is set on the membrane where the TM is formed and the ECE is formed. The preset sound pressure P (t) of the EUT with a period T satisfying the Direchle conditions is represented as a Fourier series with real terms as:

where P (t), P ₁ , B _k and C _k have the pressure measurement dimension, their definition is known in the measurement technique, ω is the angular frequency.

Indicate that the parameters P (f), P ₀ , B _k , C _k , etc. non-periodic functions are expressed as the sum of an infinite number of sinusoidal functions with infinitely small pressure amplitudes with frequencies having all possible values of -∞ to + ∞.

Moreover, in a given section of the IO simultaneously with one sensor (with one membrane), the voltage is recorded at the output of the ANF:

,

,

Where

. После вычитания в последнем блоке 33

получим основной сигнал, несущей информацию об избыточном статическом давлении P_избыт ИО пропорционально напряжению U_АНЧ. Значение U_АНЧ регистрируют на индикаторе. Далее истинное значение давления звука на выходе АНЧ определяют как: U(t)_θ-U_0θ=ΔU_АНЧ, затем

.As can be seen from the formulas, at the output of the CNs they have sound pressure P (t) ≡U (t) ≡U (θ) with a constant component U ₁ ≡P ₀ ; and variable components U _B ≡ _{B k} , U _C ≡ _{C k} ; voltage in this circuit. Therefore, the constant component of the pressure at the inlet of the ECE is equal to zero. And this circuit is an infinite resistance U ₁ for passage, i.e. U ₁ = 0. Further, the signals from the output of the ANF and UN simultaneously enter the indicator for registration and further processing and to the outputs of the subtraction unit 33. Before subtracting in block 33, the signals from the outputs of the ANF and UN provide the subtraction units 32, 36 to extract the thermal noise signal from the total signal

. After subtraction in the last block 33

we get the main signal carrying information about the excess static pressure P _excess IO proportional to the voltage U _ANF . The value of U _ANCH recorded on the indicator. Next, the true value of the sound pressure at the output of the ANF is determined as: U (t) _θ -U _0θ = ΔU _ANF , then

.

. Давление P₁ действует со стороны защитной сетки, и давление

действует через опорную трубу. При этом на выходе АНЧ после выделения напряжения теплового шума имеем электрическое постоянное напряжение

, несущее информацию о дифференциальном давлении

. Величину давления

определяют как:

. Эти напряжения регистрируют в индикаторе. Все указанные измерения проводят при наличии связи полости датчика за мембраной через опорную трубу и многочисленные опорные отверстия 18 (фиг. 1 сеч. Б-Б).Two different static pressures are set on the sensor (second position of the switch), let's say

. Pressure P ₁ acts on the side of the safety net, and pressure

acts through the support pipe. In this case, at the output of the ANF after the isolation of the thermal noise voltage, we have an electric constant

carrying differential pressure information

. Pressure value

defined as:

. These voltages are recorded in the indicator. All these measurements are carried out in the presence of the connection of the sensor cavity behind the membrane through the support pipe and numerous support holes 18 (Fig. 1 sec. BB).

. При этом на выходе АНЧ после выделения сигнала теплового шума регистрируют постоянное напряжение

, несущее информацию об абсолютном статическом давлении

, где

- атмосферное давление;

- заданное. Величину

определяют как:

. Все величины регистрируют в индикаторе. При этом на выходе УН имеем лишь сумму сигналов, сигналов шумов аппаратуры, теплового шума и внешних помех. Сигнал

на выходе УН равняется нулю.The support tube is closed by a cover and the sensor cavity (behind the membrane) is isolated from atmospheric pressure and static pressure is set on the membrane from the side of the protective mesh

. At the same time, at the output of the ANF, after isolating the thermal noise signal, a constant voltage is recorded

carrying absolute static pressure information

where

- Atmosphere pressure;

- given. Value

defined as:

. All values are recorded in the indicator. At the same time, at the output of the CN we have only the sum of the signals, the noise signals of the equipment, thermal noise and external noise. Signal

at the output, the UN equals zero.

.The sound pressure transformed by a capacitive sensor into an electric signal is matched to ultrasound, amplified in a UN and at its output have a signal corresponding to sound pressure, and is determined as:

.

. При этом на выходе АНЧ и УН. после выделения теплового шума регистрируют одинаковый сигнал, несущий информацию о звуковом давлении, т.е.

.The sensor is placed in the sound field and the sound pressure is set on the membrane (second switch position)

. At the same time, the output of the ANCH and UN. after heat noise is released, the same signal is recorded that carries sound pressure information, i.e.

.

.The true value of sound pressure is determined using the conversion factors from the outputs of the ANF and UN in the same way as in the previous paragraph, i.e.

.

от нижнего до верхнего предела определяют изменения выходного сигнала

от нижнего до верхнего значения, пропорционального изменению измеряемого давления (от

до

). При этом определяют приращение емкости ΔС=С_т±С₀; где С_т - текущее значение емкости ЕЧЭ, когда

; С₀ - начальная емкость ЕЧЭ при давлении P_ст=0. Кроме моста Р-589, для измерения

можно использовать специально разработанную аппаратуру. Рассмотрение последнего вопроса не входит в рамки предложенного изобретения.In order to register the signal from the effect of static pressure from the output of the ECHE, the ultrasonic and the UN are replaced by an alternating current bridge, in particular, of the R-589 type. In this case, when the static pressure changes

from the lower to the upper limit determine changes in the output signal

from the lower to the upper value proportional to the change in the measured pressure (from

before

) In this case, the increment of the capacitance ΔС = С _t ± С ₀ is determined; where C _t is the current value of the capacity of the ECE when

; With ₀ - the initial capacity of the ECE at a pressure P _article = 0. In addition to the R-589 bridge, for measurement

You can use specially designed equipment. Consideration of the last issue is not included in the scope of the proposed invention.

, где

- теплопроводность полиимидной пленки. Значения термоэлектродвижущей силы определяются приблизительно. Оно зависит от структуры и чистоты металлов. При температуре холодного спая 0°С используется выражение Е=Аθ+Вθ² [мкВ]. Для меди имеем постоянные А=2,76; В=0,006, области температур 0-100°С; для никеля А=-16,3; В=-0,027, область температур -200 до +100°С. Для снижения погрешности в стадии измерения принято использовать проводники для подводящих проводов из того же материала, что и основные ЧЭТ. Это условие можно выполнить, если подобрать пару проводящих проводов А, В; С, Д и А′, В′; С′, Д′ к температуре так, чтобы при любых температурах выполнялось требование Еc-Е_Д=Е_A-Е_B и Е_C′-Е_Д′-Е_A′-Е_B′. Таким образом, суммарная погрешность измерения выходного сигнала ΔЕ=ΔE_m+ΔE_n, где реальная погрешность измерения может достигать до 20%. ΔE_m, ΔE_n - погрешности термопары и подводящих проводов соответственно. Коэффициент преобразования чувствительности ЧЭТ определяют как:

, выражается в милливольтах на °С, зависит от химического состава и физической обработки материалов и изменяется в зависимости от температуры. Например, приближенное значение термоэлектрической чувствительности мВ/°С для термопар из меди и никеля определяется как разность чувствительностей, т.е. S=-(-15)+6,5=21,5 мВ/°С где 6,5 - для меди.When the heat flux Φ through the dielectric film 8, the upper 10 and lower 9 thermocouples are exposed to temperatures θ ₁ and θ _2, respectively. The relationship between the electromotive force and the temperatures of the hot and cold junctions is set by the proportionality coefficient. The heat flux is determined by the measured temperature difference, the coefficient of thermal conductivity and the thickness of the dielectric film 8 (Fig. 1 sec. A-A)

where

- thermal conductivity of the polyimide film. The values of thermoelectromotive force are determined approximately. It depends on the structure and purity of the metals. At a cold junction temperature of 0 ° C, the expression E = Aθ + Bθ ² [μV] is used. For copper, we have the constants A = 2.76; B = 0.006, temperature range 0-100 ° C; for nickel A = -16.3; B = -0.027, temperature range -200 to + 100 ° С. To reduce the error in the measurement stage, it is customary to use conductors for lead wires of the same material as the main CHET. This condition can be satisfied if you pick up a pair of conductive wires A, B; C, D and A ′, B ′; C ′, D ′ to the temperature so that at any temperature the requirement is fulfilled: EC-E _D = E _A -E _B and E _C ′ -E _D ′ -E _A ′ -E _B ′. Thus, the total measurement error of the output signal ΔE = ΔE _m + ΔE _n , where the real measurement error can reach up to 20%. ΔE _m , ΔE _n - errors of the thermocouple and lead wires, respectively. The sensitivity conversion factor CHET is defined as:

, expressed in millivolts per ° C, depends on the chemical composition and physical processing of materials and varies with temperature. For example, the approximate value of the thermoelectric sensitivity mV / ° C for thermocouples made of copper and nickel is defined as the difference in sensitivity, i.e. S = - (- 15) + 6.5 = 21.5 mV / ° С where 6.5 is for copper.

The principle of operation of the device. When the pressure ΔP changes, the layers of the metal 13 and dielectric 16 films are deformed. Due to the deformation of the membrane, the distance between the membrane 13 and the lower lining of the capacitor 12 simultaneously changes. Due to the deflection of the membrane 13, the deformation of TM 17 occurs. As a result of the deflection of the membrane, the initial capacitance of the ECE 15 C ₀ , the resistance of TM r ₀ , increments ΔС, Δr and relative change capacity ΔС / С ₀ (ЕЧЭ) and Δr / r ₀ (ТМ). The DC polarization voltage U _p from block 28 through the resistors R ₁ and R ₂ serves the metal layer 13, the screen 3 of the sensor and the screen of the cable АВКТ-6. The signal from the output of the bottom plate 12 ECE is removed through the Central core of the cable 12. The voltage U _p from the output of block 28 is fed to one of the diagonals a, b TM 17. The voltage at the output of the ECE (between the plates 12 and 13) and TM (between the other by the diagonals c, d of the bridge) is proportional to the increment ΔС / С ₀ , Δr / r ₀ , the polarization voltage, and the power supply of the TM, respectively.

To this end, TsAGI investigated silicon EECs with a membrane diameter of 4 mm, a distance between a flat membrane 6 μm thick and a lower lining 1 μm. The amplitude characteristic was determined at a sound pressure level from 0 to 11 Pa (0-131 dB), a frequency of 30 Hz.

Frequency response in the frequency range from 20 Hz to 20 kHz is at least 12-15%. The non-linearity of the amplitude characteristic is less than one percent. Channel conversion coefficient 1.26 mV / Pa. Own noise and interference at the output of the ultrasound 30-40 dB. The polarization voltage ECHE 100 V. TM resistance r ₀ = 800 Ohm created on the basis of the SE pressure pressure. 15 microns, with a diameter of 3 mm from silicon. Using this sensor, it is possible to measure sound pressure (provided that the static pressure of the EUT is zero), sound pressure and static pressure (provided that the sound pressure of the EUT is zero). The conversion coefficient of these sensors is in the range of 0.55-3.5 μV / Pa. The upper limit on the linear pressure measuring range of the sensors is at least 160 dB. Short-term and repeated short-term 170-200 dB. The voltage of the imbalance of the sensors when working with the ANCH-22 equipment from the initial value (zero) for 50 minutes was in the range of 7.5-120 μV. Supply voltage TM 5 V.

The dependences of the change in the increment of the capacitance and the output zero signal of the EHF with a solid dielectric of polyimide 6 × 9 mm in size were tested at a temperature of 25 to 100 ° C. At 100 ° С, the zero signal increased seven times from the initial value (0.468 V). At an initial sensor capacitance of 20.6 pF, with an increase in temperature to 100 ° C, the sensor capacitance increased 1.3 times. Capacitance measurement was carried out by the R-589 bridge. The sensors were glued to the surface of the strain gauge according to GOST 21615-76. The temperature was measured with a conventional thermometer.

A series of sensors were modernized at the NIIteplopribor based on the technology of plasma-chemical etching "silicon on artificial sapphire". For example, the Sapphire-22M complex includes 45 different models of absolute pressure sensors (Sapphire 22M-DA), overpressure (Sapphire 22M-DI), vacuum (Sapphire 22M-DV, Sapphire 22M-DIV "), Pressure difference (" Sapphire 22M-DD "), etc. (magazine "Instruments and control systems", 1990, No. 1 p. 27-30).

The high technical and economic effect is achieved due to the combined action of known solutions, and this distinguishes the invention from the selected analogue and prototype. A specific solution is the ability to measure sound pressure, sound pressure, (pulsations, shock, explosive, wind waves), static pressure (excess, absolute, differential, temperature, heat flow) in one design with one SE pressure and two CHET simultaneously in a given section , allows to obtain a number of advantages: isolate the signal of thermal noise and interference from the main signal, reduce the cost of the experiment, reduce the cost of materials for the manufacture of sensors, increase the noise immunity of the meter s channels, reduce the number of current wires, to extend the scope and increase the reliability.

Claims (1)

A device for measuring pressure and temperature, comprising a base from a dielectric film, a main screen formed on its surface, a capacitor plate, a membrane with an edge, for example, a toroidal profile of a flat shape or with a corrugated profile, assembled in a bag, pins connecting the plate, membrane, main a screen, a strain gauge bridge with an external circuit, while the internal cavity of the sensor is connected to the atmosphere through a capillary hole, a strain gauge bridge is formed on the membrane surface, an electric insulated from the membrane surface by a layer of dielectric film, strain gauge and capacitive sensitive elements of the sensor based on "silicon on sapphire", a protective grid, a terminal block with connectors, a support tube with a cover, a body filled with soft sealant, two resistors and a capacitor, with the upper lining the capacitive sensor element of the sensor through the cable screen is connected to the positive pole of the charge amplifier, both resistors and the second capacitor are connected at one point, the first resistor is connected to the residential cable I, with the first capacitor and the bottom plate of the capacitive sensor element of the sensor, the negative pole of the polarization source is connected to an external screen and local ground, and the sensor is equipped with low-frequency equipment, a DC power supply, a charge and voltage amplifier, a subtraction unit, an indicator, and the capacitive sensitive the element and the strain gauge bridge are connected at the same output of the DC source and supply the pressure sensor with the same voltage, and the subtraction unit is located inside the housing sensor, characterized in that two additional elements of the temperature of the hot junction are additionally introduced, are symmetrically located on each other on the upper and lower surfaces of the dielectric film, two sensitive elements of the temperature of the cold junction, the cold junction of thermocouples are located outside the device body, provide the melting temperature of the ice and they are connected between yourself and through a switch connect to the indicator, a metal ring, two potentiometric amplifiers, memory blocks, one switch, three blocks you power, and in the first position of the switch the output of the low-frequency equipment, the voltage amplifier through the switch, memory blocks, subtraction units are connected to the indicator inputs, in the second position of the switch, the outputs of the low-frequency equipment and the voltage amplifier through the switch are connected to the inputs of the three subtraction units and their output is connected with an indicator input, the outputs of two temperature sensors through potentiometric amplifiers and a subtraction unit are connected to the indicator, the output of one of the potentiometers of various amplifiers is connected to the indicator, the output of another potentiometric amplifier through memory blocks is also connected to the indicator, with the charge amplifier mounted inside the sensor housing on the bottom surface of the circuit board, the sensor housing connected to a common bus at point B of the device, on the second part of the sensor of two dielectric films and temperature sensors, through them at least ten through support holes are made, the cavity of the capacitive sensor element behind the membrane It is connected with the atmosphere through the support tube, passing through the first part of the sensor structure, consisting of a mounting plate, an air gap, a terminal block of connectors, a screen on the surface of the dielectric film and a casting compound, the air gap being formed between the first and second parts of the sensor structure, and between the first and second parts of the sensor design is a metal ring.

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