DD224970A1 - ARRANGEMENT AND PROCEDURE FOR DETERMINING CONDUCTIVITY ANALYSIS IN THE UNDERGROUND - Google Patents

Abstract

The invention relates to an arrangement and a method for determining the real and imaginary parts and the absolute square of electric and / or magnetic field components, wherein by reference to the maximum amplitude of a reference signal measurement errors due to amplitude changes of the Primaersignals be avoided. With a suitable choice of the measuring and reference field components, preferably magnetic vertical and maximum magnetic horizontal component, the results obtained with the apparatus make it possible to draw conclusions about Leitfaehigkeitsaenderungen in the underground.

Description

Field of application of the invention

The invention relates to an arrangement and a method for determining conductivity phenomena in the underground. The invention finds in the detection of conductive interfering or conductive zones, for. As in the geophysical Erzprospektion or in the search of underground metal parts, application.

Characteristic of the known technical solutions

Known technical solutions are based on the assumption that the size of the primary electromagnetic field remains constant during the measuring process. To determine the real and imaginary part of the measured variable, two transducers are used, one of which receives the measured variable and the other a reference variable. The evaluation of these quantities is done via phase detectors. The disadvantage here is that changes in the primary field strength enter into the measured variable and distort it.

Other equipment measures the amplitudes of measurement and reference size, as well as the phase shift between them, separated from each other. Here, the amplitude change of the primary field can be taken into account, however, it is necessary evaluation devices or larger-scale arithmetic units to do so.

U.S. Patent No. 3,614,600 describes a magnetic prospecting apparatus that uses real and imaginary parts as controlled variables. Variations in the primary field are corrected. The disadvantage is that two different reference quantities are to be generated, which once require an increased electronic complexity of the apparatus and which, on the other hand, necessitate resonance tuning of the magnetic pickup required in the reference channel for the respectively selected measuring frequency. Another disadvantage is that the electric field can not be used as a reference size.

Object of the invention

The object of the invention is the determination of conductivity anomalies in the underground with low equipment complexity and high accuracy.

Explanation of the essence of the invention

The technical object of the invention is to develop an arrangement and a method for the determination of conductivity anomalies in the subsurface. The invention is intended to ensure the metrological elimination of occurring Primärfeidschwankungen already the receiving side to exclude distortions of the measurement result. According to the invention the object is achieved in that an existing electric or magnetic field of natural or artificial origin is used as the primary field and in a metrological arrangement absolute square, real and imaginary part of components of this field are derived and a component of this field to form a primary field fluctuations ausschaltenden reference size is used.

The arrangement according to the invention consists of two or more identically constructed, gain-adjustable, and preferably selective amplifiers, which are preceded by two or more transducers which can receive certain components of the magnetic and / or electric field. At least one amplifier is followed by a multiplier and a low-pass filter for forming the absolute square, a multiplier and a low-pass filter for forming the real part, and a multiplier and a low-pass filter for forming the imaginary part.

-2- 64 35 3

Another amplifier, the multiplier and the low-pass filter to form the Reaiteiles directly and via a phase shifter of the multiplier and the low-pass filter to form the imaginary part downstream. Likewise, this amplifier is a rectifier with a subsequent comparator whose second input is connected to a Referenzspamiungsquelle, followed by. The output of the comparator is connected to the control inputs of the at least two amplifiers.

At least one amplifier is a measured variable, for. B. a component of an electric or magnetic field supplied (measuring circuit). Another amplifier is a reference size, z. B. another component of the same electric or magnetic field supplied (reference circle). The output of an amplifier of a measuring circuit is supplied to the formation of the square of the sum of both inputs of a multiplier and then passed through a low-pass filter or integrated. Furthermore, the same output signal is supplied to each input of two further multipliers. To form the real part of the second input of a Multipiizierers the output signal of the amplifier in the reference circuit is fed directly and then passed through a low-pass filter or integrated. The second input of the other multiplier, the output signal of the amplifier in the reference circuit is passed after passing through a phase shifter for forming the imaginary part and then passed through a low-pass filter or integrated. The output signal of the amplifier in the reference circuit is further supplied to a rectifier, rectified and compared by a comparator with a reference voltage source. The output signal obtained at the comparator is fed to all input amplifiers and serves for the simultaneous gain control of all amplifiers. The method according to the invention uses two or more sensors which pick up certain components of the magnetic and / or electric field and convert them into an electrical voltage. Advantageously, the recording of the vertical magnetic component as a measured variable and the maximum horizontal magnetic component as a reference variable. However, any other combinations are possible, wherein a field component is to be selected as the reference variable whose amplitude changes only slightly by the influence of the secondary field. These are e.g. the horizontal magnetic component perpendicular to the transmitter direction or the vertical electrical component.

In the method according to the invention, the electrical voltages supplied by the transducers are preferably supplied to selective amplifiers whose amplification can be adjusted within wide limits. In this case, the reference variable is supplied to the reference circuit, while one or more measured variables are supplied to one or more measuring circuits. The reference variable amplified reference variable is rectified and compared by means of a comparator with a constant reference voltage. The signal obtained at the output of the comparator is used to gain adjust all input amplifiers to the same gain value. This gain value is equal to the quotient of the reference voltage and the maximum voltage amplitude of the reference variable. In the reference circuit one obtains an amplitude-constant signal at the amplifier output as a result of this gain control, while the signal at the amplifier output in the measuring circuit varies depending on the existing measuring conditions. To form the real part, the signal of the amplifier output in the reference circuit is fed directly to a multiplier, to form the imaginary part of a further multiplier via a 90 ° phase shifter. The remaining free inputs of the multiplier, the output signal of the amplifier of a measuring circuit is supplied, in the case of the square squaring the two inputs of a multiplier are respectively supplied to the same measurement signal of a measuring channel; The gain setting is done in the same way over the reference circle. The multiplied signals are each filtered by a low-pass filter or supplied to an integrator, so that one obtains at their outputs real or imaginary part of the measured variable based on the maximum amplitude of the reference variable or the square of the ratio measured to reference size.

If it is assumed that amplitude changes of the primary signal have the same effect on the measurement and reference variables, then they remain unaffected by the quotient of the amplitude of the measurement signal to the amplitude of the reference signal - real and imaginary part or absolute square.

embodiment

The invention will be explained in more detail with reference to an embodiment.

The figure shows the schematic diagram of the arrangement for a measuring channel. The measuring devices supplied by the two transducers

(M) and reference signals (R) are applied at points 1 and 2. They are amplified v-fold by the adjustable input amplifiers 3 and 4. The amplification can be made selectively. The reference signal after amplification has the size B = ν R; R = R cos ω t,

the measuring signal has the size

A = ν M; M = M cos (ω t - * - φ).

The multiplier 6 multiplies the amplified measurement signal A by the amplified reference signal B. After the product has passed through the low-pass filter 8, the real part of the measurement signal relative to the maximum amplitude of the reference signal G is obtained at point 18:

C-, J | - I cos

where U = amplitude of the comparison signal = constant.

The multiplier 7 forms the product of the measuring signal A and the phase shifted in the phase shifter 5 by 90 ° reference signal B *, which supplies the imaginary part H at point 19 after passing through the low-pass filter 9:

2 l

ІЗ. --Sin Sin T

^ά R

The multiplier 15 provides K = A ² . From this one obtains at the output 17 the square of sums

2 ^A IT, Mx 2

^d R

-z- 64 35 3

The multiplication M / R is effected despite multiplication of the signals on the special feedback of the v-fold amplified and rectified by the rectifier 10 reference signal C, which is compared by the comparator 11 with an amplitude-stable DC voltage U, the Verstärkseinstellorgane 13,14 of the input amplifier. 3 ; 4. If one uses a rectifier 10 as a peak rectifier, one obtains for

C = ν R.

The feedback effects a gain adjustment of the input amplifiers 4 such that C = U. Consequently, for ν = U / R and since all other input amplifiers are set to the same gain value ν, one obtains for the products

2 IJ ²

S = AB = v ^ M R = ^ MR

2 ^l

=. 2- f / "cos <f + cos (2 O t + f) 7 _ R"

2 ^A P = AB ² = 5- I / "sin <P + cos (2 u) t + f + J) _7.

When squaring the measuring signal, one obtains

K = A ² = V ² M ² = U ² (| -) ² cos ² ζ tft + <f).

The low-pass filtering or integration of the signals E, F, K suppresses the high-frequency components, so that one real, imaginary part and absolute square G, H, L receives at the outputs 18, 19, 17.

Claims (7)

-1- 64 35 3 Invention claims: 1. An arrangement for determining conductivity anomalies in the underground, characterized in that the arrangement of two or more identically constructed, preferably selective amplifiers, which are preceded by two or more specific components of the magnetic and / or electric field receiving transducer, that one or more amplifiers in each case one the square of the sum, the real part and the imaginary part forming multiplier are followed by subsequent low passes that at least one amplifier a real part forming multiplier with subsequent low pass filter directly and a imaginary part forming multiplier with subsequent low pass filter indirectly via a phase shifter and that the same output of this amplifier, a rectifier is connected downstream, which is connected together with a reference voltage source via a comparator to the control inputs of all amplifiers. 2. A method for determining conductivity anomalies in the underground characterized in that electrical and / or magnetic field components are taken, that at least one of these field components as a measured variable and another under the influence of the secondary field minimally changing component of the same field is used as a reference and all amplifiers be set to the same gain by the amplified output of the reference quantity after comparison with a reference voltage. 3. The method according to item 2, characterized in that the formation of the magnitude of the square of the measured variable by supplying the output signal of at least one amplifier in the measuring circuit to both inputs of a Muitiplizierers and subsequent low-pass filtering or integration takes place. 4. The method according to item 2, characterized in that the formation of Realteiis the measured variable by supplying the output signal of at least one amplifier in the measuring circuit to an input of a multiplier and supply of the output signal of the amplifier in the reference circuit to the second input of the multiplier and subsequent Tiefpaßfilterung or integration he follows. 5. The method according to item 2, characterized in that the formation of the imaginary part of the measured variable by supplying the output signal of at least one amplifier in the measuring circuit to an input of a multiplier and supply of the output signal of the amplifier in the reference circuit after a phase shift of 90 ° in a phase shifter circuit to the second input of the multiplier and subsequent low-pass filtering ng or integration takes place. 6. The method according to item 3 to 5, characterized in that a plurality of measurement variables are supplied to a plurality of measuring circuits simultaneously and that the real, imaginary parts and squares of these quantities are formed by a corresponding number of Multipiizierern, low-pass filters or integrators and a phase shifter. 7. The method according to item 2 to 6, characterized in that predominantly electrical and / or magnetic fields in a frequency range of 20 to 100,000 Hz are measured. For this 1 page drawing