RU2415392C1 - Device for remote pressure measurement - Google Patents

Abstract

FIELD: instrument making. ^ SUBSTANCE: device is composed of the following components: scanning device and transmitter-responder. Scanning device is composed of the following components: driving oscillator, power amplifier, duplexer, transceiving antenna, phase doubler, phase divider into two, narrowband filter, phase metre, phase detector, registration unit, frequency detector, trigger, double balance switch. Transceiver is arranged in the form of multi-lead delay line on surface acoustic waves, comprising interdigital transducer. ^ EFFECT: improved validity of remote identification of pressure sensor number and pressure it measures by elimination of reverse operation effect. ^ 3 dwg

Description

The proposed device relates to instrumentation and can be used in remote pressure information collection systems in various industries.

Known pressure sensors are based on various physical principles (copyright certificates of the USSR No. 922.086, 1.000.806, 1.177.698, 1.290.113, 1.368.677, 1.493.895, 1.508.114, 1.686.322, 1.769.010, 1.818. 560, 1.831.669, 1.835.250; RF patents Nos. 2.058.020, 2.244.908; US patents Nos. 4.387.601, 4.395.915, 4.562.742; Polish patent No. 1119.860; Japanese patent No. 50-9.190; Busurin VI “Optical and fiber-optic sensors.” Quantum Electronics, No. 5 p.901-944 and others).

Known devices generally provide pressure measurement directly at their installation sites.

However, in some cases, in various industries, the need arises for remote pressure measurement with high accuracy.

Of the known devices closest to the proposed is a "Device for remote measurement of pressure" (RF patent No. 2.244.908, G01L 9/00, 2002), which is selected as a prototype.

The specified device contains a scanning device and a transponder.

The scanning device includes a phase detector, the necessary condition for which is the presence of a reference voltage having a constant initial phase and a frequency equal to the frequency of the received phase-shifted (PSK) signal. The specified reference voltage directly from the received QPSK signal by multiplying and dividing the phase of the received QPSK signal by two.

However, this causes the phenomenon of “reverse operation”, which is due to abrupt transitions in the phase of the reference voltage, which is released from one state φ _s to another φ _s + π under the influence of noise, short termination of reception, and other destabilizing facts.

This is easy to show analytically.

The phenomenon of “reverse operation” is due to the uncertainty of the initial phase of the reference voltage, which is extracted directly from the received PSK signal. With equally probable values of the variable, the phase component of the signal: φ ₁ = 0 and φ ₂ = π there is no sign that would allow you to "bind" the phase φ _{c of the} reference voltage to one of the phases of the signal (Fig.3, c). Therefore, the phase of the reference voltage always has two stable states φ _с and φ _с + π.

The reference voltage required for synchronous detection of the received PSK signal (figure 3, c)

- манипулируемая составляющая фазы, отображающая закон фазовой манипуляции в соответствии с модулирующим кодом M(t) (фиг.3, б), причем

при Кτ_э<t<(к+1)τ_э и может изменяться скачком при t=Кτ_э, т.е. на границах между элементарными посылками (К=1, 2, …, N-1);Where

- the manipulated component of the phase, displaying the law of phase manipulation in accordance with the modulating code M (t) (Fig.3, b), and

at Kτ _e <t <(k + 1) τ _e and can change abruptly at t = Kτ _e , i.e. at the borders between elementary premises (K = 1, 2, ..., N-1);

τ _e , N - the duration and number of chips that make up a signal of duration T _s (T _s = τ _e · N);

Δφ is the phase shift caused by deformation of the membrane 16,

stands out directly from the received QPSK signal. For this, a 5-phase doubler, a 6-phase divider into two, and a narrow-band filter 7 are used.

At the output of the doubler of the 5th phase, a harmonic oscillation is formed (Fig. 3, g)

, то в данном колебании манипуляция фазы уже отсутствует. Это колебание длится по фазе на два в делителе 6 фазы на два и выделяется узкополосным фильтром 7 (фиг.3, и)As

, then in this oscillation phase manipulation is already absent. This oscillation lasts in phase by two in the phase divider 6 into two and is distinguished by a narrow-band filter 7 (Fig. 3, and)

The obtained harmonic oscillation u ₃ (t) is used as a reference voltage and is fed to the second (reference) input of the phase detector 8, to the first (information) input of which the received FMN signal u ₁ (t) is supplied (Fig. 3, c). As a result of synchronous detection at the output of the phase detector 8, a low-frequency voltage is generated (Fig. 3, k)

Where

which is proportional to the modulating code M (t) (Fig. 3, b). The structure of the latter is determined by the structure of the interdigital transducer (IDT) (figure 2).

The low-frequency voltage u _N (t) (Fig. 3, k) contains information about the number of the remote pressure sensor and is fixed at the first input of the registration unit 10.

However, this information may be distorted due to the phenomenon of “reverse operation”, which is caused by spasmodic transitions of the phase of the reference voltage from one state φ _s to another φ _s + π under the influence of interference, short-term termination of reception and other destabilizing factors.

Indeed, if you make a division similar to the previous one, but add the angle 2π to the argument beforehand, which does not change the initial voltage, then after dividing the phase by two, you get the voltage shifted in phase by π

Consequently, the ambiguity of the phase of the obtained reference voltage follows from the fission process itself.

The physically indicated two-valued phase is due to the unstable operation of the phase divider 6 into two. Therefore, the phase of the reference voltage always has two stable states φ _с and φ _с + π. The transition from one state to another occurs at random points in time, for example t ₁ t ₂ , t ₃ , t ₄ (Fig.3, d) under the influence of various destabilizing factors. At the same time, at the output of the phase detector 8, a distorted analogue u _ni (t) (Fig. 3, c) of the modulating code M (t) (Fig. 3, b) is distinguished, which does not allow to reliably determine the number of the remote pressure sensor.

(фиг.3, д) не позволяет также достоверно измерить фазовый сдвиг Δφ, пропорциональный измеряемому давлению Р.Distorted Reference Voltage

(Fig.3, d) also does not allow to reliably measure the phase shift Δφ proportional to the measured pressure R.

An object of the invention is to increase the reliability of remote determination of the number of the pressure sensor and the pressure measured by it by eliminating the phenomenon of "reverse operation".

The constant problem is solved in that a device for remote pressure measurement, containing, in accordance with the closest analogue, a scanning device and a transponder, while the scanning device contains a serially connected master oscillator, a power amplifier, a duplexer, the input-output of which is connected to a transceiver antenna, a doubler phases, phase divider into two and a narrow-band filter, a phase detector and a recording unit connected in series to the output of the duplexer, the second input of which is connected via a phase meter nen with the second output of the master oscillator, and the transponder is made in the form of a multi-tap delay line for surface acoustic waves, including an interdigital transducer, which is made in the form of two comb systems of electrodes deposited on the surface of the sound duct, the electrodes of the combs are connected by buses that are connected to the microstrip transceiver antenna, while a thin membrane and a reflective array are placed on the sound duct, differs from the closest analogue in that the scanning device is equipped with a -frequency detector, a trigger switch and double balanced, and to the output of notch filter frequency detector connected in series, and a double balanced trigger switch, a second input coupled to an output of the narrowband filter and the output being connected to the second input of the phase detector and the phase meter.

The structural diagram of the scanning device is presented in figure 1. The structural diagram of the transponder is shown in Fig.2. Timing diagrams explaining the principle of operation of the remote pressure sensor are shown in figure 3.

The scanning device is a transceiver with a directional or non-directional antenna and consists of a serially connected master oscillator 1, a power amplifier 2, a duplexer 3, the input-output of which is connected to a transceiver antenna 4, a phase doubler 5, a phase divider 6 into two, a narrow-band filter 7, a frequency detector 18, a trigger 19, a double balanced switch 20, the second input of which is connected to the output of the narrow-band filter 7, a phase detector 8, the second input of which is connected to the output of the duplexer 3, and the unit 10 registration. A phase meter 9 is connected to the second output of the master oscillator 1, the second input of which is connected to the output of the double balanced switch 20, and the output is connected to the second input of the registration unit 10.

The transponder is made in the form of a multi-tap delay line for surface acoustic waves (SAW), which is a discrete analog implementation of a digital transverse filter. The role of taps in such a filter is played by the VPSh, which consists of two comb systems of electrodes deposited on the surface of the sound duct 11. The electrodes of each of the combs are connected to each other by buses 14 and 15. The tires, in turn, are connected to the microstrip transceiver antenna 12. On the sound duct 11, in addition, a thin membrane 16 and a reflective grid 17 are arranged.

The taps of the multi-tap delay line are evenly distributed along the surface of the sound pipe 11 with a step Δh = V · τ _e ,

where V is the speed of the surfactant, it is approximately five orders of magnitude less than the speed C of the propagation of electromagnetic waves (V << C);

τ _e - the duration of the elementary premises.

Therefore, the transponder is a piezocrystal with an aluminum thin-film piezoelectric transducer deposited on its surface and a set of reflectors. The transducer is connected to a microstrip transceiver antenna 12, which is also made on the surface of the piezocrystal.

Remote pressure sensor operates as follows.

The master oscillator 1 generates a high-frequency oscillation (figure 3, a)

where U _s , w _s , φ _s , T _s - amplitude, carrier frequency, initial phase and duration of high-frequency oscillations,

which, after amplification in the power amplifier 2, through the duplexer 3 enters the transceiver antenna 4 and is radiated by it, it is captured by the microstrip transceiver antenna 12 and excites IDT on the SAW.

The basis of the operation of the device on a surfactant is three physical processes:

- conversion of the input electrical signal into an acoustic wave;

- the propagation of an acoustic wave along the surface of the sound duct and its reflection;

- the inverse transformation of the surfactant into an electrical signal.

For direct and reverse surfactant conversion, IDT is used, the operation of which is based on the fact that the electric fields in space and time created in the piezoelectric crystal by the electrode system 13 cause elastic strains that propagate in the crystal as a surfactant due to the piezoelectric effect. The center frequency and bandwidth of the IDT is determined by the placement of the electrodes 13 and their number. IDT is fabricated by standard photolithography methods and by etching a thin metal film deposited on a piezoelectric crystal. The capabilities of modern photolithography make it possible to create IDTs operating at frequencies up to 3 GHz.

A pressure P is applied to the thin membrane 16, causing it to deform. The speed of the surfactant in the region of the membrane 16 will change and the phase of the acoustic wave reflected from the lattice 17 will also change in accordance with the deformation of the membrane 16.

The acoustic wave is modified in a unique way, depending on the topology of the transponder. Then the reflected acoustic wave undergoes the inverse transformation into an electromagnetic signal, which enters the microstrip antenna 12 and is radiated by it into space (Fig. 3, c)

The specified QPSK signal is controlled by a transceiver antenna 4 and through a duplexer 3 is fed to the first input of the phase detector 8 and to the input of the phase doubler 5. At the output of the latter, harmonic oscillation is formed (Fig. 3, d)

Where

, то в данном колебании манипуляция фазы уже отсутствует. Это колебание делится по фазе на два в делителе 6 фазы и выделяется узкополосным фильтром 7 (фиг.3, д)As

, then in this oscillation phase manipulation is already absent. This oscillation is divided in phase into two in the phase divider 6 and is allocated by a narrow-band filter 7 (Fig.3, d)

The resulting harmonic oscillation due to the phenomenon of "reverse work" has an unstable phase. This oscillation is applied to the first input of the double balanced switch 20 and to the input of the frequency detector 18. When the phase of the reference voltage jumps by 180 °, for example, at times t ₁ and t ₃ (Fig. 3, d), the output of the frequency detector 18 short positive pulses appear, and when the phase jumps at -180 ° at time t ₂ and t ₄ (the phase of the reference voltage returns to its original state), negative short pulses appear (Fig. 3, g). Alternating pulses from the output of the frequency detector 18 control the operation of the trigger 19, the output voltage of which (Fig.3, h), in turn, controls the operation of the double balanced switch 20.

совпадает, например, с нулевой фазой принимаемого ФМн-сигнала u₁(t) (фиг.3, в), на выходе триггера 19 образуется отрицательное напряжение (фиг.3, з) и двойной балансный переключатель 20 находится в своем первоначальном положении, при котором опорное напряжение

(фиг.3, д) поступает с выхода узкополосного фильтра 7 на второй (опорный) вход фазового детектора 8 без изменения.In steady state, when the phase of the reference voltage

coincides, for example, with the zero phase of the received QPSK signal u ₁ (t) (Fig. 3, c), a negative voltage is generated at the output of the trigger 19 (Fig. 3, h) and the double balance switch 20 is in its original position, at which reference voltage

(Fig.3, d) comes from the output of the narrow-band filter 7 to the second (reference) input of the phase detector 8 without change.

(фиг.3, д) с выхода узкополосного фильтра 7 поступает на второй (опорный) вход фазового детектора 8 с изменением фазы на - 180°. Это позволяет устранить нестабильность фазы опорного напряжения

(фиг.3, д), вызванную скачкообразным ее изменением под действием помех и связанную с ней «обратную работу». При этом на второй (опорный) вход фазового детектора 8 будет поступать опорное напряжение (фиг.3, и)When the phase of the reference voltage jumps by 180 °, due, for example, to the unstable operation of the phase divider 6 into two under the influence of interference, the trigger 19 at time instants, for example, t ₁ and t ₃ positive short pulses from the output of the frequency detector 18 is transferred to another steady state. In this case, the output voltage of the trigger 19 at times t ₁ and t ₃ becomes and remains positive until the next jump in the phase of the reference voltage at times t ₂ and t ₄ , which return the phase of the reference voltage to its original state. The positive output voltage of the trigger 19 (figure 3, h) transfers the double balanced switch to another stable state, in which the reference voltage

(Fig. 3, e) from the output of the narrow-band filter 7 it enters the second (reference) input of the phase detector 8 with a phase change of −180 °. This eliminates the instability of the phase reference voltage

(Fig. 3, e) caused by its abrupt change under the influence of interference and the associated “reverse work”. In this case, the second voltage (reference) input of the phase detector 8 will receive the reference voltage (Fig.3, and)

with stable phase.

At the output of the phase detector 8, a low-frequency voltage is generated (Fig. 3, k)

Where

which is fixed at the first input of the registration unit 10.

(фиг.3, и) поступает на второй вход фазометра 9, на первый вход которого подается гармоническое колебание (фиг.3, а) с второго выхода задающего генератора 1. Фазометр 9 измеряет фазовый сдвиг Δφ, пропорциональный измеряемому давлению Р, который фиксируется на втором входе блока 10 регистрации.Reference voltage at the same time

(Fig. 3, i) is fed to the second input of the phase meter 9, the first input of which is fed into harmonic oscillation (Fig. 3, a) from the second output of the master oscillator 1. The phasometer 9 measures the phase shift Δφ proportional to the measured pressure P, which is fixed at the second input of block 10 registration.

Therefore, the frequency detector 18 provides detection of the moment of occurrence of "reverse operation", and the trigger 19 and the double balance switch 20 eliminate it. The registration unit 10 fixes the number of the remote pressure sensor and the pressure P measured by it with high accuracy.

The scanning device provides a sequential survey of all remote pressure sensors, registration of their numbers and measured pressures. A remote pressure sensor is necessary in cases where a direct (contact) pressure measurement cannot be performed.

The main advantage of automatic teleindication systems with the use of surfactant transponders is the ability to manufacture passive, i.e. small-sized transponder requiring no power supply.

The transponder used provides the ability to remotely read the pressure information that it carries, an unlimited number of times, in automatic mode.

Another advantage is the possibility of combining the functions of energy re-emission, coding of constant number information and the function of a pressure sensor in one device with a simple design.

A positive property of a surfactant transponder can also be considered low costs for long-term operation (lack of battery and long MTBF).

Thus, the proposed device in comparison with the prototype provides an increase in the reliability of determining the number of the remote pressure sensor and the pressure measured by it. This is achieved by eliminating the phenomenon of “reverse operation” by stabilizing the phase of the reference voltage, which is extracted directly from the received PSK signal. The specified stabilization of the phase of the reference voltage is provided by the use of a frequency detector, a trigger and a double balanced switch. Moreover, the frequency detector provides detection of the moment of occurrence of "reverse operation", and the trigger and double balance switch eliminates it.

Claims (1)

A device for remote pressure measurement, comprising a scanning device and a transponder, the scanning device comprising a serially connected master oscillator, a power amplifier, a duplexer, the input-output of which is connected to a transceiver antenna, a phase doubler, a phase divider into two, and a narrow-band filter connected in series to the output of the duplexer is a phase detector and a recording unit, the second input of which through a phase meter is connected to the second output of the master oscillator, and the transponder is made in de multi-tap delay line on surface acoustic waves, including an interdigital transducer, which is made in the form of two comb systems of electrodes deposited on the surface of the sound duct, the electrodes of the combs are connected by buses that are connected to the microstrip transceiver antenna, while a thin membrane and a reflective one are placed on the sound duct grating, characterized in that the scanning device is equipped with a frequency detector, a trigger and a double balanced switch, and to the output of narrow bands th filter connected in series with a frequency detector, and a double balanced trigger switch, a second input coupled to an output of the narrowband filter and the output being connected to the second input of the phase detector and the phase meter.

Images