CS197842B1 - Circuit for measurement of magnetic suspeptibility of rocks - Google Patents

Abstract

The circuit for measuring the magnetic susceptibility of rocks is intended for portable geophysical instruments. It measures susceptibility by means of a change in the inductance of the sensing coil, caused by an approaching rock sample. The purpose of the invention is to enable mathematical processing of the measured values before their display on the display. The sensing coil (7) is connected to a measuring oscillator (6), connected via a time counter (5) and a control circuit (2) to a reciprocating counter. A reference stable oscillator (1) is connected to the input of the reciprocating counter and a digital display (3) is connected to the output. The circuit is useful in the field of geophysics for interpreting anomalies of the Earth's magnetic field and in the field of petrography for determining rock types.

Description

The object of the invention is a circuit for measuring the magnetic susceptibility of rocks, which comprises a sensing coil, to which the rock sample approaches during measurement.

Magnetic susceptibility is one of the basic physical properties of a character. limiting rock. Its knowledge is necessary for the interpretation of anomalies of the Earth's magnetic field. It allows to identify related types of rocks, distinguishable only by a detailed petrographic analysis. It is determined using instruments with a sensing coil. The rock sample is approached to the sensing coil and the inductance change induced by the rock sample is measured. The inductance change is a measure of the magnetic susceptibility of a rock. Since the inductance change can also be caused by disturbances, for example by changing the temperature of the sensor coil, in the known wiring and susceptibility measuring devices, a compensation coil is also included in the sensor coil. Both coils are connected to the bridge and exposed to the same interference, but the rock is only approaching the sensing coil. Inductance variations of the compensation coil are used to compensate for inductance changes induced by disturbances in the sensing coil.

Disadvantages of the prior art wiring and devices for measuring the magnetic susceptibility of rocks result from the bridge coil wiring system. The electrical parameters of the two coils must be as different as possible, which complicates the manufacture and adjustment of the device. The bridge must be balanced before approaching the rock sample to the sensing coil, usually in two components, and after approaching the rock sample to the sensing coil, its balance must be repeated, often with other controls. Manual balancing is laborious and lengthens the measurement process, automatic balancing is complex and thus expensive. The bridge arrangement requires several working ranges, which increases the complexity of the instrument and complicates the measurement process. Although balancing the bridge before approaching the sample eliminates the effect of the static component of spontaneous temperature variation of the sensing and compensating coil, automatic removal of the effect of linearly spontaneous variation is difficult to perform and therefore does not occur in prior art devices.

The known portable rock magnetic susceptibility measuring devices form the sensing coil of the secondary winding of the phase discriminator powered by the crystal controlled oscillator. The disturbed equilibrium of the discriminator arising after the sensing coil approaches the rock is restored by changing the capacitance of the capacitor connected in parallel to the sensing coil. The magnetic susceptibility of the rock is read on the capacitor scale.

The operation of these instruments is also complicated and the measuring procedure is lengthy. When resetting the instrument and then measuring it, it is necessary to manipulate two control elements while observing the indicator indicator while holding the instrument at a constant distance from the rock to be examined, which causes difficulties in the field. If the operator did not select the measuring range correctly, he must change it and repeat the procedure.

The complex handling causes a relatively long time interval between zeroing and actual measurement, during which disturbing, uncompensated effects of temperature changes, distorting the measured values of magnetic susceptibility, are acting on the sensor coil. In addition, from 197 842 the counting of the measured values on the pointer is not accurate.

These disadvantages are eliminated by the circuit for measuring the magnetic susceptibility of rocks according to the invention, which consists in that the sensing coil is connected to a measuring oscillator connected via a timer counter and a control circuit with a return counter, on whose input a reference stable oscillator is connected and data output digital display, the control circuit, with two control inputs, is also connected to the counters with reset outputs and with a return counter with a blocking output.

Interference, in particular the adverse effect of temperature changes on the sensing coil, is reduced when the timer counter is connected to the second control input of the control circuit by an interval output.

The advantages of wiring for measuring the magnetic susceptibility of rocks according to the invention are manifested in the operation of the apparatus, in its accuracy and in the reduction of its size and weight. The tether apparatus according to the invention has only two operating elements, a pushbutton switch and a fixed device only one switch. There is no need for range switches, but the dynamics of the instrument are so great that the magnetic susceptibility values can be measured in a range of several orders of magnitude. The measurement procedure is shortened by the time of finding the correct measuring range. The instrument is lighter, it does not contain a compensation coil, the time interval between zeroing and measurement is reduced to a minimum, so the adverse effect is substantially reduced. temperature changes per sensor coil. With stable, non-portable devices, even this limited temperature effect is automatically compensated. The instrument is equipped with a digital display for reading the measured values, which also significantly simplifies and speeds up the work of the operator. The connection according to the invention allows the tester to be operated with only one hand.

A specific example of wiring is shown in the accompanying drawings, in which Fig. 1 is a block diagram suitable for portable devices, and Fig. 2 is a block diagram suitable for stable, laboratory devices.

The central part of the circuit for measuring the magnetic susceptibility of rocks according to the invention is a return counter 2, whose data outputs 12 are connected to the data inputs 13 of the digital display 6 for displaying the values of the measured magnetic susceptibility. The counter input £ of the return counter J is connected to the pulse output 14 of the reference stable oscillator 1. The blocking input 11 of the return counter 2 is connected by the β blocking output 16 of the control circuit 4 and its directional input 9 to the directional output 15 of the control circuit 4. The first reset input 10 of the return counter 2 is connected to the first reset output 16 of the control circuit 4, the second reset output 21 of the control circuit J is connected to the second reset input 22 of the timer counter 5. The sensor coil 7 is connected to the measuring oscillator 6. * 25 is connected to the signal input 24 of the timer counter 5 * The timing output 23 of the timer counter 5 is connected to the timer in step 20 of the control circuit 4.

197 842

In the wiring for portable rock magnetic susceptibility measuring devices, the control circuit 4 is connected by a first control input 18 via a first switch 27 and a second control input 19 via a second switch 28 to a power supply, not shown.

The wiring according to the invention, suitable for portable devices, operates in five bars which correspond to five possible states of the control circuit 4. By actuating the wiring according to the invention the reference stable oscillator 1 and the measuring oscillator 6 oscillate and oscillate for all five clocks. This is the initial first bar.

The return counter 2 is blocked by a blocking signal that is supplied to the blocking input 11 from the blocking output 17. The timer counter 5 is permanently reset by a signal that is supplied from the second resetting output 21 to the second resetting input 22.

Upon approaching the rock to the sensing coil 7, the first trigger 27 is energized by closing the first switch 27 from the power supply (not shown) to the first control input 18. The control circuit thereby moves to a second cycle during which the control circuit 4 sends the first reset input 10 pulse to reset the counter 2. The signal on directional output 15 sets the counter 2 to be added. The second clock ends automatically and the control circuit 4 goes to the third clock.

In the third measure, the blocking signal supplied to the blocking input 11 is extinguished. The return counter 2 adds the pulses supplied from the crystal oscillator 1 to the counting input 8. At the same time, the reset signal fed to the second resetting input 22 of the timer counter 5 expires. 25 to the signal input 24. After adding a fixed number of pulses, the timer counter 5 sends a timing signal to the timer input 20. The control circuit thus goes to the fourth measure.

During the fourth measure, a blocking signal is present on the blocking output 17 and the return counter 2 is thus blocked. At the same time, on the second reset output 21 there is a second reset signal which resets the Timer Counter 5. With the arrival of the fourth clock, the state of the directional output 15 of the control circuit 4 changes, thereby reversing the counter 2 to subtraction. During the fourth measure, the rock moves away from the sensing coil 7, the second sensor 28 closes, and the control circuit 4 moves to the fifth measure by receiving a trigger signal at the second control input 19.

The blocking signal on the blocking output 17 disappears and at the same time the second resetting signal on the second resetting output 21 also disappears. The return counter 2 reads the pulses applied to the counting input 8. The timer counter 5 increases its status. After adding the same number of pulses as during the third cycle, a timing signal is generated at the timing output 23, which causes the control circuit 4 to pass to the initial first cycle. The state of the return counter 2 displayed by the digital display 3 determines the susceptibility of the measured rock.

197 842

The circuit as described above is particularly suitable for small portable devices for measuring the magnetic susceptibility of rocks.

For more precise laboratory devices, a second variant of the circuit according to the invention is more suitable, see FIG. 2, with compensation for linearly spontaneous variation of the inductance of the sensing coil 7. In this circuit, the timer counter 5 is connected by an interval output 26 with a second control input 16 of the control circuit 4. The circuit according to the invention then operates in thirteen bars that correspond to thirteen possible states of the control circuit. The initial first cycle occurs by oscillating the reference stable oscillator 1 and the measuring oscillator 6, which oscillate at 10% of all clocks. The timer counter 5 is reset by a second reset signal applied to the second reset input 22. The return counter 2 is blocked by a blocking signal supplied from the blocking output 17 to the blocking input 11. The second circuit is switched by switching the first switch 27 and applying the first control signal to the first control input 18. In this measure, the first reset signal 16 generates a first reset signal resetting the return counter 2, since there is no directional signal at the directional output 15, the return counter 2 is set to subtract. at the same time the second reset signal on the second reset input 22 of the timer counter 5 disappears. The timer counter 5 therefore counts the pulses supplied from the signal output 25 to the signal input. 24. After adding a predetermined number of pulses, a timing signal is generated at the timing output 23 by which the control circuit J is transferred to the fourth measure. The blocking signal applied from the blocking output 17 to the blocking input 11 stops counting the return counter 2. At the same time, the timer counter 5 is reset by a second reset signal applied to the second resetting input 22. In the fifth measure, the return counter 6 is blocked by a blocking signal applied to the blocking input 11. However, the timer counter 5 counts the pulses supplied from the signal output 25 to the signal input 24. During this measure, a rock sample is inserted into the sensing coil 7. After adding a preselected number of pulses, which may be different from the third measure, a signal that is applied to the second control input 18. The control circuit 4 passes this signal to the sixth bar.

By the directional signal supplied from the directional output 15 to the directional input 8, the return counter 8 is set to add. The timing counter 5 is reset by a second reset signal applied to the second reset input 22 from the second reset output 21. In the seventh cycle, the reset counter 5 is reset by the first reset signal applied to the first reset input 10 and adds pulses from pulse output 14 to the counting input 8. At the same time, the timer counter 5 stops being reset by the second reset signal that was applied in the sixth clock to the second reset input 22. The timer counter 5 adds pulses from the signal output 25 to the signal input 24. After adding the same number of pulses as in the third clock at the timing output 23, a timing signal by which the control circuit 4 is converted into the eighth clock. The return counter 2 is blocked by a blocking signal applied to the blocking input 11, the timer counter 5 is reset by a second reset signal applied to the second resetting input 22. During the ninth time, the reset counter 2 is reset by a reset signal applied to the first resetting input.

197 842 and adds pulses from pulse output 14 to counting input 8. At the same time, the timer counter 5 stops being reset by the second reset signal that was applied to the second resetting input 22 in the eighth clock. Timer counter 5 adds pulses coming from signal output 25 to signal input 24. After adding the same number of pulses as in the third measure, a timing signal is generated on the timing output 23, by which the control circuit 4 is converted into the tenth measure.

The blocking signal applied from the blocking output 17 to the blocking input 11 stops the counting of the return counter 2. At the same time, the timer counter 5 is reset by a second reset signal applied to the second resetting input 22. At the eleventh clock, the return counter 2 is blocked by the blocking signal supplied to the blocking input 11. the timer counter 5 stops zeroing at the arrival of the eleventh bar and counts the pulses supplied from the signal output 25 to the signal input 24. During the eleventh bar, the rock sample is withdrawn from the sensing coil. After adding the same number of pulses as during the fifth measure, an interval signal 26 is output at the interval output 26, which is applied to the second control input ·).

There is no directional signal on the directional output 15, the return counter 2 is therefore set to subtract, the timer counter 5 is reset by a second reset signal applied to the second reset input 22 from the second reset output 21.

In the thirteenth clock, the return counter 2 stops being blocked by the blocking signal supplied to the blocking input 11 and therefore begins to subtract the pulses supplied from the pulse output 14. At the same time the second reset signal that was applied to the second resetting input 22 of the timer counts down. pulses supplied from the signal output 25 to the signal input 24. After adding the same number of pulses as during the third cycle, a timing signal is generated at the timing output 23 by which the control circuit 4 is converted to the initial first cycle. The status of the return counter 2 displayed on the digital display 3 indicates the magnetic susceptibility value of the rock sample being measured.

Claims (2)

A circuit for measuring the magnetic susceptibility of rocks comprising a sensor coil, characterized in that the sensor coil (7) is connected to a measuring oscillator (6) connected via a timer counter (5) and a control circuit (4) to a return counter ( 2), on whose computer input (8) is connected the reference stable oscillator (1) and on its data output (12) digital display (3), while the control circuit (4), with two control inputs (18, 19), is the counter (2.5) is also connected to the reset outputs (16, 21) and the return counter (2) is additionally locked (17). Wiring according to claim 1, characterized in that the timer counter (5) is connected by an interval output (26) to a second control input (19) of the control circuit (4).