SU1659928A1 - Device for measuring electrical conductivity and magnetic permeability - Google Patents

Abstract

The invention relates to a measurement technique and can be used to control conductive and magnetic materials. The purpose of the invention is achieved by the introduction of a control unit 27, a square-voltage pulse shaper 1, a subtracting transformer 4, two pairs of amplifying transistors 5, 6 and 7.8, two cumulative capacitors 9, 10, four current generators 21-24, two source followers 17.18 on field-effect transistors, two output transformers 19, 20, and two sample and hold cells 25, 26. The device also contains two conductors 2, 3, forming inductances, six controllable keys 11-16. Zil.

Description

The invention relates to a measurement technique, in particular to multiparameter sensors of physical quantities, and can be used to monitor conductive and magnetic materials by parameters of electrical conductivity and magnetic permeability, as well as dimensional values of products from conductive and magnetic materials with known parameters. electrical conductivity and magnetic permeability.

The purpose of the invention is to improve accuracy.

FIG. 1 shows a diagram of the device; Fig. 2 is a control block diagram; in fig. 3 is a timing diagram of the control signals of the control unit.

The proposed device for measuring electrical conductivity and magnetic permeability (Fig. 1) consists of a former 1 impulse voltage pulse generator, two conductors 2

and 3 forming inductances, subtracting transformer 4, two pairs of amplifier transistors 5. 6 and 7, 8, two storage capacitors 9 and 10, six controlled keys 11-16, two source followers on field-effect transistors 17, 18, two output transistors 19, 20, four current generators 21-24, two sample and hold cells (or ADC) 25.26 and a control unit 27, the output of the driver 1 is connected to the first terminals of the conductors 2, 3, the second terminals of which are connected to the primary winding of the transformer 4, the midpoint of which is connected to zero a first terminal of the secondary winding of the transformer 4 is connected to the combined bases of transistors 5 and 8 and via resistor 28 is connected to zero potential bus to which are connected via a resistor 29, the combined base of transistors 6, 7, a second terminal connected to the secondary winding of the transformer 4 by (A

WITH

oh eaten oh oh k

00

pairwise combined emitters of transistors 5, 6 and 7, 8 through controlled switches 11, 12 and first current generator 21 are connected to the first power line 30, pairwise combined collectors of transistors 5, 7 and 6, 8 are connected respectively to the gates of field-effect transistors 17, 18 , with the first terminals of the storage capacitors 9, 10, through the keys 13, 14 with the second power bus 31 and through the keys 15, 16 with the outputs of the current generators 22, 23, the inputs of which are connected to the second power bus 31, to which the drains of the field effect transistors 17 are connected , 18, whose origins are connected to bases the common transistors 19, 20 and through the load resistors 32, 33 are connected to the common bus, the emitters of the output transistors 19, 20 through the radial resistors 34.35 are connected to the output of the current generator 24, the input of which is connected to the second power bus 31, the collectors of the transistors 19, 20 through the load resistors 36, 37 are connected to the first power supply bus 30, and the collector of the transistor 20 is also connected to the information inputs of the sample and storage cells or (ADC) 25, 26, the outputs of which are connected to the outputs 38, 39 of the device, the first output 40 of the control unit 27 is connected to the input of the imaging unit 1, the second output 41 to the combined control inputs of the keys 13, 14, the outputs 42, 43 to the inputs of the keys 11, 12, the output 44 to the integrated control inputs of the keys 15, 16, outputs 45, 46 to the control the input inputs of the sample and hold cells (or ADC) 25, 26, the product 47 of controlled material is placed in the scattering field of the first conductor system 2,

The control unit (Fig. 2), which forms the timing diagram of the control signals, contains a pulse generator 48, a pulse counter 49 with a variable conversion factor determining the number of pulses in a series, a trigger 50 with a counting input, five And 51-55 elements, one element NOT 56, one delay element 57 with direct output, one delay element 58 with inverted output, differentiation element 59 of positive differential, outputs of counter 49 and one element OR 60. The order of operation of the control unit is explained by the time diagram, ennoy FIG. 3, the numbers in the timing diagram correspond to the output numbers of the control unit 27.

A device for measuring electrical conductivity and magnetic permeability works as follows.

A series of pulses at the output 40 of the control unit 27 starts the driver 1

square-wave voltage pulses that excite conductors 2, 3, forming inductances, around which a magnetic field is excited. Since the conductors 2 and 3 are identical, the currents flowing through them are the same, so the voltage on the secondary winding of the transformer 4, determined by the difference in currents in the primary windings of the transformer

0 4 is zero. The voltage at the output of the device is also equal to zero. When a product from a controlled material is introduced into the magnetic field of the first conductor 2, eddy currents are induced in the product material, the field of which is directed opposite to the current field in the conductor, resulting in the inductance of conductor 2 decreasing and the voltage proportional to the secondary winding of the subtractive transformer 4 decreases.

0 conductivity of the material.

At the time of rise of the pulse of the excitation current, the magnetic field is generated not only by the field of eddy currents, but also by the field magnetizing the material of the product, which are directed opposite to each other. Therefore, at the output of the transformer 4, the resulting signal is equal to the difference of signals from the floor of the vortex

0 currents in the material of the product and the magnetization field, and after calming the eddy currents, the signal is formed only as a result of the magnetization of the product material, and the voltage of this signal uniquely determines the magnetic permeability of the product material.

During the first series of excitation pulses, the electrical conductivity of the material of the product is measured, and during

0 of the second series - its magnetic permeability. The series of pulses are formed in the control unit 27 by means of a counter 49. When the most significant bit of the counter (in FIG. 2, trigger 50) is in the state O,

5, a first series of pulses is formed to measure the electrical conductivity of the material, which is estimated from the sum of the difference signals on the secondary winding of the transformer 4 on the leading front of the excitation pulse and on its flat part. When the most significant bit of the meter is in state 1, a second series of excitation pulses is formed to measure the magnetic permeability of the material of the product

5, which is estimated from the voltage of the differential signal over the time interval of the excitation pulse after the eddy currents have settled down before the pulse decays.

For optimal signal processing, a charge accumulation circuit is used.

At the beginning of each series, a control pulse is generated at the output 41 of the control unit, as a result of which the keys 13, 14 close, and the storage capacitors 9, 10 are charged before the voltage of the second power bus 31. After the keys 13, 14 are opened, the entire first pulse series during the time interval of the existence of induced eddy currents, i.e., at the leading edge of the excitation current pulse, the switch 11 closes and the generator current 21 enters the emitters of transistors 5, 6, as a result of which the latter are opened, the generator current 21 is redistributed between they are proportional to the voltage on their bases; and capacitors 9, 10 are discharged by the collector currents of transistors 5, 6 to different voltage levels.

After opening the key 11 on the flat part of the excitation current pulse, the switch 12 closes the signal at the output 43 of the control unit, the branch current of the generator 21 to the emitters of transistors 7 and 8, as a result of which the latter are opened and a further discharge of capacitors 9, 10 occurs, proportional voltage on the bases of the transistors 7, 8. But since the transistors 5, 6 and 7, 8 are connected to each other, then during the closure of the key 12, the charge of the capacitor is summed to the first result entered during the closure of the key 11. So as the signal voltage at the first and second time intervals of the excitation current pulse have opposite polarity, then the charges of each capacitor at the first and second time intervals are summed. Thus, the resulting voltage at the capacitors 9.10 corresponds to the sum of the signal voltages at the leading edge excitation pulse and on its flat part. During the subsequent pulses of the first series, the closing sequence of the keys 11 and 12 is maintained, the discharge of the capacitors continues, with the result that at the end of the series the charging voltage of the capacitors 9. The 10 becomes equal to the sum of the charges in the time interval of one pulse. To increase the gain of the input stage, consisting of amplifying transistors, storage capacitors, emitter switches and a current generator 21, the device uses a charging circuit of storage capacitors containing switches 15, 16 and current generators 22, 23. Switches 15, 16 are closed along The signals from the output 44 of the control unit 27 simultaneously with the closure of the keys 11 and 12.

The current of the generators 22, 23 is set so that the voltage of the charge of capacitors 9, 10 at the end of a series with a balanced circuit, i.e., in the absence of the product in the magnetic field of the first conductor 2, is equal to half the voltage of the second power bus 31 i.e. E / 2, and the difference in voltage between the charges of capacitors 9 and 10, corresponding to the maximum voltage of the information signal, was also equal to Е / 2. The output transistors 19, 20 voltage from the storage capacitors is transmitted through the source repeaters on the field-effect transistors 17, 18. The output 5 transistors 19, 20, connected in a differential amplifier circuit, serve to convert the difference voltage on the storage capacitors 9, 10 to a voltage relatively common tires. The voltage accumulated at the collector of transistor 20 at the end of a series is charged to the sample and hold cell 25 by the signal from the output 45 of the control unit. If the device requires a digital equivalent of measured parameter tapes, an ADC is used instead of the sample and hold cell. An analog voltage at the input of which is converted to a digital code by a signal from the output 45 of the control unit;

0 is stored until the next access to the ADC. Thus, the voltage at the output of the sample and storage cell (or the code at the output of the ADC) 25 is equivalent to the electrical conductivity of the material being monitored

5 products.

At the beginning of the second series of excitation pulses, the keys 13, 14 are closed by the signal from the output 41 of the control unit, through which the storage capacitors close to the voltage of the second power bus 31. After opening the keys 13. 14 during the time interval of the excitation pulse after the eddy currents calm down key 12, causing the current

5, the generator 21 enters the emitters of the transistors 7, 8, redistributing between them in proportion to the voltage on the bases of the transistors, which is determined in this time interval by the magnetic permeability of the material of the product. The capacitors 9, 10 are discharged by the collector currents of the transistors 7, 8. Simultaneously with the key 12, the keys 15, 16 are closed, through which the capacitors 9, 10 are charged by the currents of the generators 22, 23. During the second series of excitation pulses of the capacitors 9 , 10 accumulates, and at the end of a series, the voltage at the output of transistor 20 becomes proportional to the difference magnetizing current

Claims (1)

the material of the product, that is, the magnetic proportionality of the material. According to the signal from the output 46 of the control unit 27, the collector voltage of transistor 20 is entered into a sample and hold cell 26 (or converted into a digital code if an ADC is used), and a voltage (or digital code) appears at output 39, unambiguously determines the value of the magnetic permeability of the product. Apparatus of the Invention A device for measuring electrical conductivity and magnetic permeability, comprising two conductors forming inductances, is distinguished so that, in order to improve accuracy, sequentially connected control unit and a square voltage pulse shaper, a subtracting transformer, are inserted into it. two pairs of amplifying transistors, two storage capacitors, three pairs of controllable keys, four current generators, two source repeaters on field-effect transistors, two outputs x transistors and two cells of sampling and storage, the output of the driver connected to the beginnings of two conductors, the ends of which are connected to two terminals of the transformer primary winding, the midpoint of which is connected to the common bus, to which the first and second transformer secondary windings are connected through resistors , also connected to the bases of the first, fourth and second and third amplifying transistors, respectively, the emitters of the first, third and fourth transistors are pairwise combined and through the first and second the swarm of keys is connected to the output of the first current generator, whose input is connected to the first power bus, pairwise combined collectors of the first, third and second, fourth amplifying transistors are connected to the gates of the first and second field-effect transistors, respectively, connected to the first and second storage capacitors, the second terminals of which are connected to the common bus through the third and fourth keys, are connected with the second power bus and through the fifth and sixth keys are connected to the outputs of the BTopojQ and the third current generator, the inputs of which are connected to the second power supply, to which the drains of the first are connected The second field-effect transistors, whose sources through the first and second load resistors are connected to a common bus and connected to the bases of the first and second output transistors, the emitters of which are connected through separation resistors to the output of the fourth current generator, whose input is connected to the second power bus, output collectors transistors through the third and fourth load resistors are connected to the first power line, the collector of the second output transistor is connected to the information inputs of the first and second cells the samples and the storage, the outputs of which are connected to the first and second outputs of the device, the control inputs of the first and second keys are connected respectively to the second and third outputs of the control unit, the pairwise combined control inputs of the third, fourth, fifth and sixth keys are connected respectively to the fourth and the fifth outputs of the control unit, the sixth and seventh outputs of which are connected to the control inputs of the first and second sample and storage cells, respectively. 3 Phi21