SU970395A1 - Device for simulating electromagnetic induction - Google Patents

Description

The invention relates to electrical modeling and can be used in geophysics in solving electrical prospecting.

A modeling device is known comprising a bath with electrolyte and models, an excitation generator with an antenna system for creating a uniform electromagnetic field in the bath area, a measuring probe including an electromagnetic field sensor (near-electromagnetic electromagnetic dipoles), a frequency converter, and separate transmission lines, for example , transformer or optical, which are galvanically isolated with a receiver-recording device 11.

The closest in technical essence to the invention is a simulator / also containing a bath with electrolyte and a model, an excitation generator with an antenna system, a measuring, a probe, a frequency converter, a local oscillator and a heterodyne voltage former 2.

Known simulators with satisfactory accuracy work up to frequencies of 5-10 MHz, since

The existing measuring probes of the simulators do not provide sufficient accuracy due to the residual antenna effect (the common-mode component of the noise excited by the electromagnetic field) due to the connecting wires and the switch of the receiving dipoles that connect them to the frequency converter. The length of the connecting wires is sufficient for the parasitic pickup from the electromagnetic fields at high frequency to be noticeable. With careful separation of the measurement signal from the receiving-recording devices, for example, by transmitting optical signals through the optical fiber, it was experimentally established that the antenna effect occurs only in the aforementioned area. Receiver directivity pattern: 5 electromagnetic dipoles, at higher frequencies, therefore, this distortion is more distorted, the smaller the dimensions of the receiving dipoles. This causes the inaccuracy of measurement of the components of the electromagnetic field.

Large dimensions modeling

30 baths (meters) of known devices. consequently, the large dimensions of the models of geoelectric structures also create difficulties in wounding a number of three-dimensional problems. Basically, these difficulties are associated with the production of large models, heavy in size, and their installation into the bath. That device is not mobile. In order to reduce the linear dimensions of the bath, for example, by a factor of two, it is necessary to ensure that non-frequency overlap, while observing the similarity factors, increase the frequency range of the device by four times (r where X is the wavelength in the electrolyte, f is the frequency of the electromagnetic field, p- electrolyte resistivity). In order to maintain linear resolution, the dimensions of the receiving dipoles should be reduced to the same extent. Therefore, a very urgent task is to reduce interference at the high-frequency edge of the band. The purpose of the invention is to improve the accuracy of modeling at higher frequencies. This goal is achieved by the fact that in the known device containing the electrolytic bath, the generator of a uniform electrom of a magnetic field, the radiating antenna, a local oscillating unit, turn on the electr. magnetic dipoles, measuring unit, three transmission lines and body measurements Hfcfflf probe, the first input of which is connected through the first transmission line to the output of the local oscillator, the second input through the second transmission line - to the output of the unit specifying the order of electromagnetic dipoles, and the output through the third transmission line - to the input of the measuring unit, moreover, the measuring probe contains electromagnetic dipoles, which are connected to the inputs of the corresponding amplifiers of the intermediate frequency converters and the heterodyne voltage driver, The output of which is connected to the combined inputs of intermediate frequency amplifiers, and the input is the primary input of the measuring probe, each transmission line is made in the form of series-connected LEDs, a light guide and a photodiode, and the intermediate frequency converters of the measuring probe are located inside the coils of an electromagnetic dipole and The time probe and the intermediate frequency filter are introduced into the measuring probe, the input of which is connected to the combined outputs of the converter amplifiers. frequency, and the output is the output of the probe. the input of the time selector is the second input of the probe, and the outputs are connected to the control-. to the corresponding inputs of the respective intermediate frequency converters. Figure 1 shows a block diagram of a device for simulating electromagnetic induction; Fig 2 is a functional diagram of the measuring probe. The device contains an electrolytic bath 10 with models, a generator 2 of a uniform electromagnetic field, a radiating antenna 3, a measuring probe 4, three-component electromagnetic dipoles (Hj, Well, H), coils have mutually perpendicular winding on a cubic insulating base, electromagnetic dipoles 8 and 9 two-component (E and EV) intermediate-frequency transducers 10-14, intermediate frequency filter 15, LED 16, light guide 17, photodiode 18 measuring unit 19, shaper 20 heterogeneous hHjjdro voltage, photodiode 2 1, light guide 22, light-emitting diode 23, local oscillator 24, time selector 25, photodiode 26, light guide 27, light-emitting diode 28, block 29 specifying the order of switching on the electromagnetic dipoles. The device works as follows ... Electromagnetic field created in the bath area 1 by the antenna 3, excites in the electromagnetic dipole x 5-9 of the measuring probe 4 an electrical signal. The signal from one of the dipoles 5-9, depending on the arrival of the resolving potential (pulse) from the time selector 25, comes through one of the amplifiers-converters 10-14 intermediate intermediate-frequency. You are in the form of an intermediate frequency at the input-filter 15 intermediate frequency, placed outside the magnetic dipoles. The filtered and amplified by the current active filter electric signal of the intermediate frequency is supplied to the LED 16, where it is converted into luminous flux and transmitted via the photodiode 18 through the photodiode 18 to the block 19. To provide a frequency conversion mode of the converters 10-14 to the diagonal of the balanced circuit from the heterodyne generator 20 the voltage is applied to the voltage of the local oscillator 24. The frequency of the heterodyne oscillation is determined by the external local oscillator 24, the oscillation of which is converted by means of the LED 23 into light radiation, which e through the light guide 22 enters the photodiode 21, where it is converted again

In the electrical signal, which in the imaging unit 20 takes the standard level.

The sequence of operation of amplifiers-converters 10-14 of the intermediate frequency is set by inclusive pulses coming from the time selector 25, which in a certain order open the base-emitter transitions of transistors of the amplifiers-converters of intermediate frequency, thereby sequentially polling each measuring channel.

Electromagnetic dipoles and transform amplifiers. Intermediate frequency switches are made structurally as a separate unit connected to intermediate frequency filter 15 by heterodyne voltage shaper 20 and time selector 25 through a connector and together with LED 16, photodiodes 21 and 26, light guides 17, 22 and 27 constitute the measurement zones 4.

The intermediate frequency filter 15, similarly to the known devices, contains a 4-metric resonant LC-circuit 30 and an additional active low-frequency RC-filter 31, which improves its matching with the light 16.

The heterodyne driver 20 consists of a photoamplifier 32 and a limiter 33, the input of the photoamplifier is connected to the photodiode 21, and the output with a limiter, where the heterodyne voltage takes the standard level and shape.

The time selector 25 consists of a photoamplifier 34, a three-bit binary counter divider 35 and a decoder 36. Code electric pulses from block 29 are converted by light-emitting diode 28 into light, which are fed via light-guide 27 to photodiode 26, which are converted again into an electrical signal. The photo selector-enhanced 34 time selector 25 pulses go to a three-digit counter divider 35, where it is set to a predetermined state. With the help of the delimiter 36, the state of the meter triggers is converted into an 8-bit parallel code with five independent line outputs. At the same time, two or more outputs allow the potential pulse to occur. Not using three bits are the beginning or end of the switching frequency cycle converters-.

Claims (2)

1. USSR author's certificate In 572807, cl. G 06 G 7/48, 1977. 2. USSR author's certificate 0 No. 329537, CL G 06 G 7/48, 1972 (prototype). 2B Z9 // / S A 9 gz yy at g "