Device for measuring the induced current in the resistance bridge of an electric initiator based on a gallium arsenide crystal

Abstract

FIELD: electrical measuring technology.SUBSTANCE: invention relates to automated measuring systems for induced current in the resistance bridge of an electrical initiation device (EID), which is part of objects during their testing for exposure to electromagnetic fields of various origins. The automated measuring system for induced current based on a gallium arsenide crystal consists of software, a multi-channel optical interrogator, an electric field strength meter, and a new induced current sensor, which is a gallium arsenide crystal attached to the end of a multi-mode optical fibre with a diameter of 125 mcm and a step refractive index profile. The crystal is in thermal contact with a resistive element made in the form of a metal film applied to a dielectric ceramic frame-substrate, which acts as a filament bridge for the EID.EFFECT: reduction in the dimensions of the induced current sensors and a reduction in the sensitivity threshold for measuring the values of the induced current flowing in the EID resistance bridge when testing objects for explosion safety when exposed to electromagnetic fields of various origins.1 cl, 2 dwg

Description

[0001] Technical field.

[0002] The invention relates to the field of electrical measuring technology, namely to measuring the induced current in the heating bridge of an electrical initiation means (EIM) included in the composition of objects during their testing for exposure to electromagnetic fields (EMF) of various origins.

[0003] In accordance with the requirements and terminology of OTT 1.2.10-2001, objects containing ESI must undergo explosion safety tests when exposed to electromagnetic fields of various origins. During testing, it is necessary to measure the magnitude of induced currents in the electrical circuits intended for activating the ESI. The current sensor is placed in the housing of the ESI, and the current flowing through the ESI's heating bridge is measured. The ESI's heating bridge may be replaced with an equivalent one with a resistance identical to the standard one. The vast majority of ESI manufactured in Russia have a heating bridge resistance of 1 to 7 ohms. The housing of the ESI with the induced current sensor placed within is called a special assembly.

[0004] Technique level.

[0005] A device for monitoring the electrical parameters of pyrotechnic devices is known (see patent RU 2 602 994 C1, published on 20.11.2016), containing an analog-to-digital converter, a voltage meter, a resistance calculator, a demultiplexer, a test current generator, a current limiter, and a control result generation unit.

[0006] The disadvantage of this technical solution is the strong influence of the measuring system on the measurement results, caused by the presence of a galvanic connection between the ESI filament bridge and the induced current sensor, as well as the influence of the measuring lines on the structure of the electromagnetic field affecting the test object.

[0007] A system for measuring induced currents in a resistive element of an electric explosive device (EED) is known (see patent RU 2 664 763 C1, published 08 / 22 / 2018).

[0008] This system comprises an induced current signal generator, a duplex fiber-optic communication line, and an interface converter for communication with a computer. The signal generator comprises a scale amplifier with a controlled gain, an induced current primary transducer, an absolute signal value extraction module, a peak detector and an analog-to-digital converter, an optical transmitter, and an optical receiver with a control digital signal decoder. The interface converter comprises a control signal generator, an optical digital receiver, a microprocessor for signal pre-processing, and a high-speed USB interface generator.

[0009] The resistive element of the EED under test is connected to the scale amplifier input, which is also connected to the standard power supply circuit of the device. A temperature sensor, which is thermally coupled to the resistive element of the EED, can also be connected to the scale amplifier input. The scale amplifier is designed as a microwave signal detector with a logarithmic dependence of the output signal on the induced high-frequency current on the resistive element of the EED.

[0010] The disadvantages of this technical solution are:

[0011] - strong influence of the measuring system on the measurement results, caused by the presence of a galvanic connection between the filament bridge of the ESI and the scale amplifier of the measuring system;

[0012] - the presence of electronics of the measuring system (scale amplifier, communication lines and optical transmitter) inside and outside the ESI, which leads to a change in the structure of the acting electromagnetic field when testing small-sized objects (the dimensions of the object are comparable to the dimensions of the measuring system).

[0013] A method for testing systems containing electric explosive devices for resistance to the effects of external electromagnetic fields in the composition of objects and a device for implementing it are known (see patent RU 2 593 521 C1, published 10.08.2016).

[0014] According to this method, a multi-channel test system for assessing the resistance of electric explosive devices to electromagnetic interference contains a test interference generator, an EMF emitting antenna, a receiving antenna located in the area of ​​the test object and connected to a field strength meter, a conversion device, a measuring communication line with the test object, a control device, placed on a test site.The mobile test bench is equipped with an optical multi-channel interrogator, an interface, a meter for the level of emitted test EMF, a device for automatic control of the system's operating modes, synchronization of the operation of all its elements, processing of experimental data and documentation of test results with the provision of precise time synchronization of all elements of the system with a radiating antenna for the formation of an external test EMF with specified spatial and polarization parameters of radiation, a power amplifier for the test EMF signal with a software-controlled generator of standard test signals, a multi-channel device for converting signals of equivalent EMF, a passive multi-channel splitter.

[0015] In this system, the equivalent of the EVU can be implemented with a fiber-optic connector for inputting the optical signal of the interrogator and receiving the optical signal reflected by the Bragg grating, a feed-through optical connector of a three-channel sensitive element - a fiber-optic current-to-temperature converter of the EVU equivalent, with an arrangement inside the EVU housing of sensitive elements on fiber-optic current-to-temperature converters made of optical fiber with built-in Bragg gratings, structurally combined with the equivalents of the igniter filaments and installed on the printed circuit board of the device for converting signals of the equivalents of electric igniters of the EVU, connected to the electrical connector of the source for initiating the operation of the EVU, installed in one end of the EVU, the second end of which is made with a threaded connection for installing the equivalent of the EVU in place of the standard EVU of the tested object.

[0016] In a dual-filament EVU, three sensitive elements on Bragg gratings, each several millimeters in size, can be used, which are formed in a single optical fiber, spaced several centimeters apart along the fiber, and combined with electrodynamic equivalents of the igniter filaments into a single structure.

[0017] The equivalent of the filament can be made in the form of a frameless spiral wire resistor, the diameter and length of which are matched to the diameter and linear size of the fiber Bragg grating, while the active resistance of the equivalent is selected equal to the resistance of the filament (from 0.6 to 12.0 Ohm), and a reduction in its inductive resistance is ensured by bifilar winding of the spiral.

[0018] The disadvantages of this technical solution are:

[0019] - complexity of manufacturing a special assembly;

[0020] - the impossibility of placing fiber-optic current-to-temperature converters inside the standard housing of the electronic device, the linear dimensions of which are a few millimeters (due to the dimensions of the fiber-optic connector and the minimum permissible bending radius of the fiber, which are about 10 mm);

[0021] - high sensitivity threshold of induced current sensors of the measuring system.

[0022] The closest in technical solution and chosen by the authors as a prototype is a device for measuring the induced current in the glow bridge of an electric initiation means (see patent RU 2 831 340 C1, published 04.12.2024).

[0023] This device consists of a multichannel optical interrogator, an electric field strength meter, a passive optical N-channel splitter, and an induced current sensor. The induced current sensor is a Bragg grating formed in the core of a single-mode optical fiber with a diameter of 50 μm. The film is deposited on top of the grating, which acts as the ESI filament bridge and has a resistance identical to that of the ESI filament bridge. Induced current sensors, whose resonant frequencies are spread across the spectrum in the range from 1460 to 1620 nm, are connected to the interrogator via optical splitters. The total length of the fiber optic connections from the interrogator to the sensor does not exceed 50 meters. The induced current sensors are installed in the housings of standard, cooled ESIs, which are filled with thermal insulation material.The device contains an automated workstation with software for recording and processing results with the ability to recalculate the magnitude of the shift of the Bragg resonance of the lattice into the amplitude of the induced current according to the calibration curve.

[0024] The disadvantages of this technical solution are:

[0025] - significant dimensions of the induced current sensor, which do not allow them to be placed in the housings of small-sized ESI, the linear dimensions of which are a few millimeters;

[0026] - high sensitivity threshold of induced current sensors of the measuring system.

[0027] The technical result, which the proposed invention is aimed at achieving, is a reduction in the dimensions of induced current sensors and a reduction in the sensitivity threshold for measuring the values ​​of induced current flowing in the incandescent bridge of the ESI, when testing objects for explosion safety when exposed to electromagnetic fields of various origins.

[0028] Disclosure of the essence of the invention.

[0029] The invention utilizes a new induced current sensor in a device for measuring induced current, consisting of software, a multichannel optical interrogator, and an electric field strength meter. This sensor consists of a gallium arsenide crystal attached to the end of a multimode optical fiber with a step refractive index profile. The crystal is in thermal contact with a resistive element, which is a metal film deposited on a dielectric ceramic frame substrate. This film acts as an equivalent of the ESI's incandescent bridge. The sensor's metal film is manufactured so that its resistance is identical to that of the incandescent bridge of a standard ESI. The total length of the fiber-optic connections from the interrogator to each sensor should not exceed 20 meters.

[0030] The proposed device utilizes cooled standard ESIs, whose housings house an induced current sensor based on a gallium arsenide crystal. The sensor's metal film is connected to the contacts of the standard ESI filament bridge using a silver wire with a diameter of 7 μm. The copper metal film with a resistance of 6 ohms is approximately 10 nm thick and 600 μm long. The copper layer thickness is selected based on the resistance of the ESI filament bridge. When current flows through the metal film, heat is generated, which is transferred to the gallium arsenide crystal, resulting in a spectral shift of its fundamental absorption band located near 900 nm. The spectral shift of the fundamental absorption band of gallium arsenide is proportional to the current flowing through the metal film. The software converts the spectral shift of the fundamental absorption band of gallium arsenide into induced current using a calibration curve.The space inside the special assembly can be filled with thermal insulation material to minimize the impact of the environment on the measurement results.

[0031] This technical solution allows minimizing the dimensions and sensitivity threshold of the induced current sensor due to:

[0032] - using a gallium arsenide crystal as the primary measuring transducer, which has greater temperature sensitivity than the Bragg grating used in the prototype (300 pm / °C and 10 pm / °C, respectively);

[0033] - reducing the dimensions of the primary measuring transducer (the gallium arsenide crystal has the shape of a cube with dimensions of 150×150×150 μm, the Bragg grating is a cylinder with a diameter of 50 μm, a length of 5-6 millimeters);

[0034] - reducing the area of ​​the resistive element, on which heat is generated when current flows through it, to 0.075 mm 2 , which is several times smaller than the area of ​​the film deposited on the Bragg grating.

[0035] What is new in the proposed invention is the design of the induced current sensor.

[0036] The combination of essential features in the proposed invention has made it possible to reduce the dimensions of the induced current sensor, increase accuracy, and lower the sensitivity threshold for measuring the induced current in the equivalent of an incandescent bridge when testing objects for explosion safety when exposed to EMF of various origins.

[0037] Brief description of drawings.

[0038] The essence of the invention and its implementation are explained in Fig. 1, 2, where:

[0039] Fig. 1 shows a schematic diagram of a device for measuring the induced current in the filament bridge of an ESI based on a gallium arsenide crystal;

[0040] Fig. 2 shows a schematic diagram of a new induced current sensor based on a gallium arsenide crystal.

[0041] Designations in Fig. 1:

[0042] 1 - software;

[0043] 2 - Multi-channel optical interrogator;

[0044] 3 - interrogator channel;

[0045] 4 - step-index multimode optical fiber connector;

[0046] 5 - electric field strength meter;

[0047] 6 - induced current sensor based on gallium arsenide crystal;

[0048] 7 - Electric initiation device;

[0049] 8 - test object.

[0050] Designations in Fig. 2:

[0051] 9 - connecting silver wire;

[0052] 10 - solder;

[0053] 11 - dielectric ceramic frame-substrate with a coated metal film acting as a filament bridge of the ESI;

[0054] 12 - gallium arsenide crystal.

[0055] Implementation of the invention.

[0056] The created sample of the device for measuring the induced current in the ESI incandescent bridge based on a gallium arsenide crystal during explosion safety testing of objects exposed to electromagnetic fields of various origins includes: an automated workstation with software for recording and processing results (1), an optical 4-channel interrogator Fiso SPC-HR (2), a connecting multimode optical fiber (outer diameter - 125 μm, core diameter - 50 μm) with a step refractive index profile (9), a gallium arsenide induced current sensor with a metal film applied to a ceramic frame-substrate, connected instead of the standard ESI incandescent bridge (6), an electric field strength meter (5).

[0057] As a result of the study of the created device sample, the following metrological characteristics were obtained:

[0058] - resistance of the filament bridge equivalent of the induced current sensor: 5.4 Ohm;

[0059] - sensitivity threshold of the induced current sensor: no more than 0.7 mA;

[0060] - upper limit of the induced current sensor measurement range: not less than 65 mA;

[0061] - measurement error of the induced current value in the range from 0.7 to 1.2 mA: no more than 20%;

[0062] - measurement error of the induced current value in the range from 1.2 to 65 mA: no more than 4.5%;

[0063] - the rate of increase of the signal amplitude 0.1-0.9 from the maximum level: no more than 500 ms;

[0064] - dimensions of the induced current sensor: 0.25×0.8×0.15 mm.

[0065] Industrial applicability.

[0066] The proposed device for measuring the induced current in the ESI filament bridge based on a gallium arsenide crystal can be used by research and development organizations, design bureaus and any other organizations involved in testing objects containing ESI (including small-sized ones) for explosion safety when exposed to EMF of various origins.

Claims

A device for measuring the induced current in the heating bridge of an electrical initiation means (EIM) included in the composition of objects during their testing for exposure to electromagnetic fields (EMF), consisting of a multichannel optical interrogator, an electric field strength meter and an induced current sensor, characterized in that the induced current sensor is a gallium arsenide crystal fixed to the end of a multimode optical fiber with a diameter of 125 μm and a stepped refractive index profile, which is in thermal contact with a resistive element made in the form of a metal film applied to a dielectric ceramic frame-substrate, which acts as the heating bridge of the EIM, which has a resistance identical to the resistance of the heating bridge of the EIM, induced current sensors are connected to the interrogator, the total length of the fiber-optic connections from the interrogator to the sensor does not exceed 20 meters,The induced current sensors are installed in the housings of de-energized standard ESI, and the device contains an automated workstation with software for recording and processing results with the ability to recalculate the magnitude of the spectral shift of the fundamental absorption band of gallium arsenide into the amplitude of the induced current using a calibration curve.

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