RU2425398C1 - Magnetic induction measuring transducer - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device includes a magnetic induction sensor consisting of two windings; a differential amplifier; a code-controlled capacitor box. The output of the code-controlled capacitor box is connected by two switches to each capacitor in the code-controlled capacitor box. The magnetic induction sensor, code-controlled capacitor box and differential amplifier are in form of stretched rigid structure.

EFFECT: wider working frequency range and high stability of conversion coefficient of magnetic induction.

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Description

The invention relates to devices for measuring the magnetic induction of an alternating electromagnetic field in the frequency range from units of hertz to 1 MHz. Preferred applications are electrical exploration using harmonic magnetic fields: induction frequency and remote sensing, dipole electromagnetic profiling.

Known magnetic induction Converter (MIP) [1] containing a multi-turn frame on a ferrite core. The output voltage of the MIP is supplied through the supply cable to the input of a digital microvoltmeter. A significant disadvantage of the known Converter is the significant influence of stray capacitance of the supply cable with increasing operating frequency.

Also known is a magnetic induction measuring transducer [2], consisting of an induction measuring transducer and loaded onto the measuring circuit. A significant drawback of this converter, as well as [1], is the significant influence of stray capacitance of the supply cable with increasing operating frequency.

The closest technical solution is a small-sized induction converter [3], which we took as a prototype device. The prototype device consists of an air multi-turn loop, the outputs and the midpoint of which are connected to the inputs and the ground (common bus) of the pre-amplifier connected to the meter. The main advantage of the prototype device is to reduce the effects of magnetic (transverse interference) and electrical (longitudinal interference) interference due to the introduction of a high-frequency induction filter into the circuit.

However, the prototype device has significant disadvantages:

1. Significant overall dimensions (up to units of meters) of the receiving loop.

2. Significant parasitic capacitance of the receiving loop, which does not allow the expansion of the operating frequencies in the high frequency region.

3. Significant influence of stray capacitance of the lead wires from the receiving loop to the measuring device. Spurious capacitance narrows the frequency range.

4. Provides conversion of only the vertical component of magnetic induction.

The purpose of the invention is to expand the operating frequency range and increase the stability of the conversion coefficient K (V / nTl * Hz) of the proposed technical device.

This goal is achieved by the fact that in the magnetic induction measuring transducer containing a magnetic induction sensor, consisting of two windings connected in series and connected to the inputs of the differential amplifier, an additional code-controlled capacitance magazine is connected, connected to the windings and the inputs of the differential amplifier, and the output of the code-controlled capacitance store connected by two keys to each capacity included in the code-controlled capacity store, and in addition, a magnetic induction sensor, to one-manned capacity magazine and differential amplifier are made in the form of an elongated rigid structure.

Figure 1 shows the structural diagram of the proposed device.

Figure 2 presents a diagram of a code-controlled store capacity from Cmax / 2 ¹⁵ to 2 * Cmax. Figure 3 shows the dependence of the frequency on the value of the adjustable capacitance and proportional to the control code of the capacitance.

Figure 4 is a General view of the developed measuring transducer of magnetic induction for eight workers: 125 Hz, 500 Hz, 1 kHz, 2 kHz, 4 kHz, 8 kHz, 16 kHz.

The proposed device (figure 1) contains a magnetic induction sensor (MID) 1, consisting of two windings 1-1 and 1-2, connected in series, a differential amplifier 2 and a code-controlled tank store 3.

The information processing unit 4 is not included in the proposed technical solution and is provided only to explain the operation of the proposed device.

The proposed device (figure 1) works as follows. The measured magnetic induction B = B _m · sin (ω ₀ · t + φ ₀ ) is directed along the magnetic induction sensor (MID) 1-1 and 1-2 (figure 1), where B _m , ω ₀ , φ _0, respectively, the amplitude, frequency and phase shift. The output voltage of the windings MID 1 is determined by the following expression:

where K = ω ₀ · W · μ _T · μ ₀ · S, where W is the number of turns, S is the area of one turn, μ _T is the relative magnetic permeability, μ ₀ = 4π · 10 ^-7 GN / m.

In parallel to the windings of MID 1, a code-controlled capacity magazine 3 is connected. The capacity value is set from the condition:

,

,

where L is the inductance of the magnetic induction sensor, i.e. a circuit consisting of two windings and a capacitor C ₀ is tuned to resonance.

Then the output voltage of the windings is determined by the expression:

U _1p = -K · Q · B _m · cos (ω ₀ · t + φ ₀ )

U _2p = K · Q · B _m · cos (ω ₀ · t + φ ₀ )

where Q is the equivalent Q factor of the circuit, taking into account the input resistances of differential amplifier 2.

These voltages are applied to the inverting and non-inverting inputs of the differential amplifier. The output voltage of the differential amplifier without taking into account the input resistance of the differential amplifier is determined by the expression

U _out = K 2 · K · _{y · Q · B m · cos (} ω ₀ · t + φ ₀₎

where K _y is the gain of the differential amplifier 2.

The output voltage of the amplifier 2 is supplied to the information processing unit 4. Block 4 also sets the control code for the code-controlled store of tanks 3 according to n - control cores (Fig. 1).

The block diagram of the code-controlled capacity magazine is shown in Fig. 3; the variable capacitance is set as C = f (N) by setting the corresponding control code N (Fig. 3) and connecting the corresponding capacitors with variable capacitance C to the input of block 3 (Figs. 1, 4) _per = C _max / 2 ^i-1 , where i = 1,2 ... 16. Each capacitor has two keys K _i-1 and K _i-2 for connecting to the output of block 3 (figure 1).

The use of two keys ensures the elimination of capacitive asymmetry of the conclusions of the code-controlled store of capacities 2 (FIG. 2) with respect to the common connection point of MID 1 and differential amplifier 2 (FIG. 1). Capacitive asymmetry occurs when each capacitor is used to connect one key and connect all second terminals of the capacitors of the code-controlled store of capacities 3 to one point.

Capacitive asymmetry is especially large for small values of the capacitance included in the oscillatory circuit. The influence of this asymmetry is significant in the high-frequency region of the operating frequency range and causes a change in the gain of the differential amplifier (Fig. 1).

Structurally, the proposed device is made in the form of a solid candy bar, placed in a protective pipe 5 (figure 4). All the blocks in this pipe are elongated along the pipe 4. Blocks 1-3 (Fig. 1) of the device in the pipe 5 are rigidly fixed with non-conductive rings 6-1-6-5 (Fig. 4) having an outer diameter equal to the inner diameter of the protective pipes 5. To connect the proposed device to the information processing unit on the outside of the non-conductive ring 6-1 is located connector 7 (figure 4).

The proposed device was used as a measuring transducer of magnetic induction at eight frequencies: 125 Hz * 2 ^p-1 , where p = 1.2 ... 8 in the equipment for shallow sounding MCH3-8. In the proposed device, it was possible to expand by an order of magnitude the working frequency range, as well as to increase the temporal stability of the conversion coefficient.

The proposed device is tested in the field in areas with a high level of electromagnetic interference.

Thus, in the proposed device, the expansion of the frequency range is provided and the stability of the coefficient of conversion of magnetic induction into an electrical signal is increased.

Literature

1. Methodological recommendations on the method of charge with multi-component measurements in ore deposits. - October: VNIIGIS, 1991, p. 50-52.

2. G.V. Abramzon, Yu.P. Oboishev. Induction measuring transducers of variable magnetic fields. L., Energoatomizdat, 1984; p. 18-22.

3. A.K. Zakharkin. Small induction converter. Russian patent No. 2073257 from 08.23.1993 (prototype).

Claims (1)

A magnetic induction measuring transducer comprising a magneto-induction sensor, consisting of two windings connected in series and connected to the inputs of a differential amplifier, characterized in that a code-controlled capacitance magazine is connected to it and connected to the windings and to the inputs of a differential amplifier, the output of a code-controlled tank store connected by two keys to each container included in the code-controlled tank store, as well as a magnetic induction sensor, code-controlled tank store her and the differential amplifier are made in the form of an elongated rigid structure.

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