RU2006046C1 - Device for measurement of magnetic sensing of ore materials - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: device for measurement of magnetic sensing of ore materials has induction probe and circuit for automatic correction of zero signal of induction probe composed of adder, counter, digital-to-analog converter, former of time interval (pulse generator and frequency divider connected in series), flip-flop, two comparators, two voltage setting units and pickup of movement of conveyer. Circuit for automatic correction makes it possible to correct zero signal for duration of lack of ore material on moving conveyer. Correction of zero signal is performed by minimal value of signal across output of induction probe but not by average signal like in prototype device. Minimal value of signal at output of induction probe depends in lesser degree on small pieces of ore left on conveyer belt occasionally than average level of background signal at output of induction probe which provides for more accurate correction of zero signal of device. EFFECT: increased accuracy of measurements. 3 dwg

Description

 The invention relates to measuring equipment and can be used to control the quality of iron ore raw materials by magnetic susceptibility in conveyor streams.

 A device for measuring the magnetic susceptibility of ore materials containing an induction probe is a common feature with the proposed device. Based on this analogue invention, a magnetic susceptibility sensor MV-3 was developed, which is manufactured commercially by the Uralchermetavtomatika OPTP.

 The disadvantage of this known analog device is the lack of accuracy in measuring the magnetic susceptibility associated with the instability of the zero signal at the output of the sensor. Changes to the zero signal occur mainly due to changes in the ambient temperature.

 The closest technical solution to the proposed one is a device for measuring the magnetic susceptibility of ore materials containing an induction probe - a common feature with the proposed device.

 The disadvantage of this known prototype device is the lack of accuracy in measuring the magnetic susceptibility of ore materials, associated with insufficient accuracy of zero signal correction, which is due to the fact that when the device is in automatic zero signal correction mode, there may be separate small pieces on an empty conveyor belt ore material, creating some variable background level, and the device compensates for this average background level, which is not quite right no. In fact, it is not the average level of this signal that needs to be compensated, but the minimum value of this signal, which does not carry information about small pieces of ore accidentally remaining on the conveyor belt.

 The purpose of the invention is to improve the accuracy of measuring magnetic susceptibility.

 This goal is achieved by the fact that the device for measuring the magnetic susceptibility of ore materials, containing an induction probe, a pulse generator, is equipped with an adder, an ore material motion sensor, two voltage adjusters, a differentiation unit, two comparators, two pulse counters, two AND-NOT elements, a trigger integrating an RC chain, a reversible counter, a digital-to-analog converter, and the induction probe through the sequences connected by an adder and an integrating chain Connected to the output bus of the device, the output of the adder is connected via a differentiation unit to the first input of the first NAND element, the second input of which is connected to the output of the first comparator, the first input of which is connected to the output bus of the device, with the first input of the second comparator, the second inputs of the comparators are connected to the outputs of the respective voltage adjusters, the conveyor motion sensor is connected to the third input of the AND-NOT element, the output of which is connected to the reset inputs of the trigger and two pulse counters, the output of the generator is imp LSS is connected to the counting input of the first pulse counter, the output of which is connected to the counting input of the second pulse counter and to the first input of the second AND-NOT element, the second input of which is connected to the second input of the second AND-NOT element and to the counting input of the reverse counter, the control input of which connected to the trigger output, the installation input of which is connected to the output of the second comparator, the output of the second AND-NOT element is connected to the fourth input of the first AND-NOT element, the outputs of the reverse counter are connected to the corresponding inputs am analog converter whose output is connected to a second input of the adder.

 In FIG. 1 shows a schematic diagram of a device; in FIG. 2 is a timing diagram of the operation of the device; in FIG. 3 is a diagram of an induction probe.

 A device for measuring the magnetic susceptibility of ore materials contains (see Fig. 1): induction probe 1, conveyor motion sensor 2, adder 3, first 4 and second 5 voltage detectors, pulse generator 6, an integrating RC circuit (damper) 7, block differentiation 8, the first 9 and second 10 pulse counters, the first 11 and second 12 comparators (comparison elements), the first 13 and second 14 AND-NOT elements, trigger 15, counter 16, digital-to-analog converter (DAC) 17, output bus devices 18.

In the timing diagram of FIG. 2 shows:
a) an example of measuring the analog voltage at the output of the induction probe 1; b) the signal at the output of the adder 3; c) a signal at the output of an AND-NOT 13 element; d) the signal at the output of the pulse counter 10; e) the signal at the output of the trigger 15 and at the control input of the reverse counter 16.

 Used in the device of FIG. 1, the induction probe 1 contains (see Fig. 3): a magnetizing coil 31, a compensation coil 32, a first 33 and a second 34 receiving coils, a resistor 35, a capacitor 36, a sinusoidal current generator 37, an amplifier 38, a synchronous detector 39, a phase shifter 40, output bus of the induction probe 41.

 A device for measuring the magnetic susceptibility of ore materials (see Fig. 1) works as follows.

Induction zones 1 is installed under the conveyor belt, a signal 19 is generated at its output (see Fig. 2a), which carries information about the magnetic susceptibility of ore material on the conveyor belt. This signal through the adder 3 and the differentiating chain 7 passes to the output bus 18 of the device. At the second input of the adder 3 from the output of the DAC 17 is a certain voltage level U _to . at the output of the adder 3, a signal 20 is formed, which is the difference of the signal 19 and the signal U _to .

 In the absence of ore material on the conveyor belt at the output of the induction probe 1 and on the output bus 18 there is a zero signal level. Due to temperature changes, for a number of other reasons, there is a departure of the zero signal from the zero value, as a result of which an error is introduced in the measurements of magnetic susceptibility as a result of the measurement. It is necessary to automatically adjust the zero signal.

If there is ore material on the conveyor belt, then the output signal of the induction probe 1 and the output signal on the output bus 18 exceeds a certain predetermined threshold value U _p (see Fig. 2b), while the correction of the zero signal is impossible. In the circuit of FIG. 1 at the output of the AND-NOT 13 element there is a high voltage level - pulse 21 (see Fig. 2, c). This voltage level is applied to the reset inputs of the R-trigger 15 and counters 9 and 10, as a result of which the counters 9 and 10 do not receive pulses from the generator 6 and are in the initial state.

At the time of decreasing voltage 20 at the output of the adder 3 below the value of U _p 9cm. FIG. 2b), a zero signal is generated at the output of the AND-NOT 13 element (see Fig. 2, c), and a comparator 11 compares the voltage U _p with the voltage 20 at the output of the adder 3. The voltage U _p is set by the voltage adjuster 4. If the voltage is 20 less than the voltage U _p , then the signal 1 is formed at the output of the comparator 11. The same signals 1 are available at the output of the motion sensor of the conveyor 2 (the conveyor is moving), the differentiation unit 8 and the AND-NOT 14 element.

Thus, according to the decay of pulse 21 (see Fig. 2c), signal 1 is taken from the reset inputs of trigger 15 and pulse counters 9 and 10. Counters 9 and 10 begin to perceive the pulses supplied to the input of counter 9 from generator 6 and after a time T ₁ to at the output of counter 10, a pulse front 22 is formed, while at the output of counter 9 there is a zero signal, and at the output of the AND-NOT 14 element, signal 1. Impulse 22 is supplied to the counting input of the counter 16 and increases the number written in it by one, resulting which increases the absolute value of the voltage at During the DAC 17 and the voltage 20 at the output of the adder 3 abruptly decreases (from point 23 to point 24) and approaches the zero level U _o. The voltage U _о is set equal to zero, or somewhat greater than zero - the latter with a unipolar design of the device, when the voltage or current on the output bus cannot be bipolar.

Thus, as a result of the action of the pulse 22, the zero voltage level approached the value of U _about .

 At the moment of the formation of the pulse front 22, there is a signal 0 at the output of the counter 9, so there is a signal 1 at the output of the NAND 14 element. The counter 9 continues to receive pulses from the generator 6 and after a while, equal to the pulse duration 22, a signal 1 is generated , while the signal 0 is generated at the output of the AND-NOT 14 element, and the pulse 25 is generated at the output of the AND-NOT 13 element. Pulse 25 resets the counters 9 and 10 to state 0. Thus, the duration of the pulse 22 is determined by the capacity of the counter 9.

The pulse duration 22 is the delay necessary for the integrating circuit to develop a voltage jump 23-24 at the output of the adder 3, so that this jump cannot switch trigger 15 to the next time interval T ₂ . If the voltage jump is such that the voltage at the output of the adder 3 and at the output of the circuit 7 decreases below the value of U _о , then a pulse is generated at the output of the comparator 12, which switches the trigger 15 to state 1. The pulse duration makes it impossible to switch this trigger to the next time interval T ₂ due to the action of a voltage surge in the previous time interval T ₁ . In this case, the voltage surge can switch the trigger only at the current moment of time T ₁ , already after the reverse counter 16 has detected a pulse 22.

After time T ₂ after the action of the front of the pulse 22 at the output of the counter 10, the front of the pulse 26 is formed.

If during the time interval T _{2 the} zero level at the output of the adder 3 (see Fig. 2b) was changed so that for some time it was below the level U _о , then this means that the zero level of the device is really lower than the value U _о , otherwise that at this time interval the zero level exceeded the value of U _о - this means that at that time there was a small amount of ore material on the tape. The second level 12 compares the zero level at the output of the adder with the given voltage U _о . If the voltage at the output of the adder 3 is less than the value of U _о , then signal 1 is generated at the output of the comparator 12, which switches trigger 15 to state 1, and a pulse is generated at the output of the trigger 27 (see Fig. 2e). At the input of the reversible counter 16, a signal 1 is set, which means that the counter is put into pulse subtraction mode. The pulse 26 arrives at the counter 16 and decreases the number written in it by one, the voltage at the output of the adder 3 increases - from point 28 to point 29 - bringing the true current value of the zero signal (point 30) closer to the set value U _о .

 Thus, in the proposed device is compensated for the average level of the changing zero signal, and the minimum values of this level, which do not carry information about randomly remained on the conveyor belt small pieces of ore. This is precisely the advantage of this device over the prototype device.

 The voltage at the output of the induction probe and, therefore, at the output of the adder 4, has a very significant ripple, associated mainly with partial changes in the magnetic susceptibility of the ore material and with the heterogeneity of the ore material. An integrating circuit 7 is installed at the output of the adder 3, smoothing out these pulsations — the instantaneous values of the magnetic susceptibility are replaced by average values over a certain time interval (about 1-2 s).

 The damping of the output signal is introduced due to the need for automatic correction of the zero signal. Damping of the zero signal reduces its dependence on the influence of individual small pieces of ore remaining on the conveyor belt. Damping averages the zero signal.

 As for large pieces of ore that accidentally hit the conveyor belt during the correction of the zero signal, then because of each such piece an inverse pulse is generated at the output of the differentiation unit 8, which generates a pulse at the output of the AND-NOT 13 element, resetting the pulse counters 9, 10 and trigger 15 to its original state. Thus, when a large piece appears on the conveyor belt, the correction of the zero signal stops and resumes again, after the piece of ore is removed from the zone of operation of the induction probe 1.

Correction of the zero signal stops when the conveyor stops, because, in this case, small pieces of ore can be in the zone of operation of the induction probe during time T ₁ , which, when the conveyor is stopped, will distort the zero signal.

 In FIG. 3 presents a schematic diagram of an induction probe 1 used in the proposed device. The induction probe contains a magnetizing 31, a compensation 32 and two receiving 33, 34 coils, a resistor 36, a sinusoidal current generator 37, a resonant amplifier 38, a synchronous detector 39, a phase shifter 40, and an output bus 41.

 The generator 37 generates a sinusoidal current in the coils 31 and 32, EMF is induced on the coils 33 and 34. At the input of the amplifier 38, in the absence of ore material, there is a zero signal, since the coils 31 and 32 are connected in series, and the coils 33 and 34 are connected in series. When installing the probe under the surface of the ore material, an analog signal is generated at the output 41 of the synchronous detector 39, the value of which is proportional to the magnetic susceptibility of the ore material.

 The considered induction probe is used in commercially available OPTP Uralchermetavtomatika magnetic susceptibility sensors of conveyor induction MV-3.

 The technical advantage of the proposed device compared to the prototype device is to increase the accuracy of measuring the magnetic susceptibility due to increased accuracy of automatic correction of the zero signal. Improving the accuracy of the correction of the zero signal occurs because in this technical solution, the correction of the zero signal is performed according to its minimum value, which does not carry information about small pieces of ore and ore dust accidentally remaining on the conveyor belt. (56) Copyright certificate of the USSR N 1019387, cl. G 01 V 3/11, 1979.

 Mountain Journal, 1987, N 2, p. 31-35.

Claims (1)

 DEVICE FOR MEASURING THE MAGNETIC SUSCEPTIBILITY OF ORE MATERIALS, comprising an induction probe, a pulse generator, characterized in that it is equipped with an adder, an ore material motion sensor, two voltage adjusters, a differentiation unit, two comparators, two pulse counters, two AND counters, a trigger, an integrating RC circuit, a reversible counter, a digital-to-analog converter, while the induction probe is connected through a series-connected adder and an integrating circuit to device bus, the adder output is connected through the differentiation unit to the first input of the first AND element - NOT, the second input of which is connected to the output of the first comparator, the first input of which is connected to the output bus of the device, with the first input of the second comparator, the second inputs of the comparators are connected to the outputs of the corresponding voltage regulators, a motion sensor of ore material is connected to the third input of the AND element - NOT, the output of which is connected to the corresponding reset inputs of the trigger and two pulse counters, output g the pulse generator is connected to the counting input of the first pulse counter, the output of which is connected to the counting input of the second pulse counter and to the first input of the second AND element - NOT, the second input of which is connected to the second input of the second AND element - NOT and to the counting input of the reverse counter, control input which is connected to the output of the trigger, the installation input of which is connected to the output of the second comparator, the output of the second element AND is NOT connected to the fourth input of the first element AND is NOT, the outputs of the reverse counter are connected to corresponding inputs of the digital-to-analog converter, the output of which is connected to the second input of the adder.

Images