RU2149418C1 - Digital device for measuring intensity of magnetic field - Google Patents

Abstract

FIELD: magnetic measurements. SUBSTANCE: device has first generator of rectangular pulses, ferromagnetic probe with core, which is made from permalloy, which hysteresis loop has rectangularity rate which is close to 1. Output circuit of ferromagnetic probe is connected to threshold unit, which output is connected to first input of first AND gate. In addition device has serial circuit of first pulse counter, digital-to- analog converter, controlled current source, gate and ferromagnetic probe excitation circuit. Second input of first AND gate is connected to output of first generator of rectangular pulses. Goal of invention is achieved by introduced first and second RS flip-flops, second generator of rectangular pulses, T flip-flop, second AND gate, second pulse counter, OR gate and third AND gate. EFFECT: increased precision of measurements due to elimination of analog signal processing elements. 2 dwg

Description

 The invention relates to magnetic measurements and is intended to measure magnetic field strength.

 A known magnetometer comprising a generator, a nuclear magnetic resonance sensor, an amplifier, a frequency controller, a code-voltage converter, an error signal receiver, a level discriminator, a reversible counter, a recording device (AS USSR 580536, class G 01 R 33/08 , 1977). However, due to the large size of the nuclear magnetic resonance sensor, the device does not allow measuring magnetic fields in small volumes and at a small distance from the surface of ferromagnetic bodies, i.e. This device cannot be used to test samples of ferromagnetic materials.

 A device containing a flux-gate is also known, in the magnetizing winding of which is included a square-wave generator and series-connected variable and reference resistors, in parallel with which a measuring device is connected, and a series-connected amplifier, integrator, threshold unit, and indicator device are connected in series to the output winding of the flux-gate. The device allows you to measure large fields near the surface of ferromagnetic bodies by the compensation method (A. S. USSR 525902, class G 01 R 33/02, 1976). The disadvantage of this device is the large measurement error due to analog methods of processing the output signal.

 The closest in technical essence to the claimed device is the selected device for measuring magnetic field strength (AS USSR N 815690, class G 01 R 33/02, 1981), containing a rectangular pulse generator, a flux gate with a core made from permalloy with a hysteresis loop with a squareness coefficient close to unity, to the output winding of which an integrator is connected, with an output connected to the input of the amplifier, the output of which is connected to the input of the threshold block, and a measuring device, as well as ice-connected elements AND-NOT, a reversible pulse counter, a digital-to-analog converter, a controlled current source and a key, the second input of a reversible pulse counter and the first input of a logical element AND-NOT connected to the output of the threshold block, the second input of the logical element AND-NOT connected to the output generator of rectangular pulses, the output of the digital-to-analog converter is connected to the input of the measuring device. The second key input is connected to the output of the rectangular pulse generator, and the key output is connected to the magnetizing winding of the flux gate.

 The disadvantage of the known device is a prototype is the following. The prototype device includes an analog integrator and amplifier. These blocks have a number of disadvantages, the most significant of which is the temperature and time drift of the output voltage (in this case, proportional to the increment of induction in the core of the flux gate). In addition, the inaccuracy in determining the required setting for the threshold device also leads to additional measurement error. You can get rid of these disadvantages by excluding the procedures of analog integration, amplification and comparison with the set point.

 An object of the invention is to increase the accuracy of measurements by eliminating the elements of analog signal processing.

 The problem is solved using a digital device for measuring the magnetic field containing the first rectangular pulse generator, a flux gate with a core made of permalloy with a hysteresis loop with a square factor close to unity, to the output winding of which a threshold block is connected, the output of the threshold block is connected to the first the input of the first logical element AND, connected in series to the first pulse counter, digital-to-analog converter, controlled current source, key and a flux-gate excitation winding, the second input of the first logical element And connected to the output of the first rectangular pulse generator, additionally equipped with a first and second RS-trigger, a second rectangular pulse generator, a T-trigger, a second logical element And, a second pulse counter, OR logic element, and the third logical element And, and the output of the second rectangular pulse generator is connected to the first input of the second RS-trigger and the second inputs of the first and second pulse counters, second the second input of the second RS-trigger and the first input of the first RS-trigger is connected to the output of the second logical element And, the first, second and third inputs of which are connected respectively to the outputs of the first RS-trigger, the first square-wave generator and threshold element, the input of the T-trigger and the second input of the first RS-trigger is connected to the output of the threshold block, the first and second inputs of the OR gate are connected to the outputs of the T-trigger and the first logical gate And, the output of the OR gate is connected to the first input of the second counter and pulses, the output of the second RS-trigger is connected to the second input of the key, to the third input of the first logical element And and the first input of the third logical element And, the second input of the third logical element And is connected to the output of the first generator of rectangular pulses, the output of the third logical element And is connected to the first input of the first pulse counter.

 Comparative analysis with the prototype shows that the inventive device is characterized by the presence of new units: two RS-flip-flops, a second rectangular pulse generator and a pulse counter, two logical elements AND, a T-trigger, a logical element OR and their connections with other elements of the circuit.

 Thus, the claimed device meets the criteria of the invention of "novelty."

 A comparison of the proposed solution with other technical solutions shows that RS and T-flip-flops, a square-wave pulse generator, AND and OR logic elements, and a pulse counter are widely known.

 However, when they are introduced in this connection with the other elements of the circuit into the inventive digital device for measuring the magnetic field strength, the above blocks exhibit new properties, which leads to increased measurement accuracy by eliminating the elements of analog signal processing. This allows us to conclude that the technical solution meets the criterion of "significant differences".

 In FIG. 1 shows a block diagram of a digital device for measuring magnetic field strength; in FIG. 2 - time diagrams of the operation of the device.

 A digital device for measuring the magnetic field strength (Fig. 1) contains a first rectangular pulse generator 1, a flux gate 2 with a core made of permalloy with a hysteresis loop with a square coefficient close to unity, to the output winding of which 3 a threshold block 4 is connected, a threshold output unit 4 is connected to the first input of the first logical element And 5, the first pulse counter 6, the digital-to-analog converter 7, the controlled current source 8, the key 9 and the excitation coil 10 are connected in series ozond 2, the second input of the first logical element And 5 connected to the output of the first rectangular pulse generator 1, the same device contains the first 11 and second 12 RS-triggers, the second rectangular pulse generator 13, T-trigger 14, the second logical element And 15, the second pulse counter 16, the logical element OR 17 and the third logical element And 18. Moreover, the output of the second generator of rectangular pulses 13 is connected to the first input of the second RS-trigger 12 and the second inputs of the first 6 and second 16 pulse counters, the second input of the second RS-t igger 12 and the first input of the first RS-trigger 11 is connected to the output of the second logical element And 15, the first, second and third inputs of which are connected respectively to the outputs of the first RS-trigger 11, the first square-wave generator 1 and threshold element 4, the input of the T-trigger 14 and the second input of the first RS-trigger 11 are connected to the output of the threshold block 4, the first and second inputs of the OR gate 17 are connected to the outputs of the T-trigger 14 and the first logical element AND 5, the output of the OR gate 17 is connected to the first input of the second counter as pulses 16, the output of the second RS-flip-flop 12 is connected to the second input of the key 9, to the third input of the first logical element And 5 and the first input of the third logical element And 18, the second input of the third logical element And 18 is connected to the output of the first rectangular pulse generator 1, the output of the third logical element And 18 is connected to the first input of the first pulse counter 6.

The device operates as follows. In the initial state, at the output of the second RS-flip-flop 12, the voltage level is prohibiting: the passage of current from the output of the controlled current source 8 through the key 9 to the excitation winding 10 of the flux-gate 2 and pulses from the output of the first rectangular pulse generator 1 through the first 5 and third 18 logic elements , at the output of the first RS-trigger 11, the voltage level prohibits the passage of pulses from the output of the first generator of rectangular pulses 1 through the second logical element And 15, at the output of the threshold block 4 voltage level, without interfering th passage of pulses from the output of the first square wave generator 5 through the first and second logic elements 15 IA ferroprobes 2 was placed in a constant or varying over time measured field H _rev (Fig. 2). The state of the core of the flux-gate 2 is determined by the magnitude of the field N _ISM and the value of the compensating field N _k created by the current in the excitation winding 10 of the flux-gate 2. The magnitude of the compensating field is proportional to the current of the controlled current source 8, switched by key 9. For normal operation of the device, the measured and compensating fields are directed in the opposite direction.

Consider the measurement cycle. The pulse from the output of the second rectangular pulse generator 13 is fed to the second inputs of the first 6 and second 16 pulse counter, turning them into a zero state, and to the first input of the second RS-trigger 12, as a result of which the voltage level is set at the output of the RS-trigger 12: the current flowing from the output of the current source 8 to the excitation winding 10 of the flux gate 2 through the key 9 and passing through the first 5 and third 18 logic elements AND pulses from the output of the first rectangular pulse generator 1, respectively, to the input of the second counter and pulses 16 through the OR gate 17 and the first pulse counter 6. The output code of the first pulse counter 6, as a result of summing the pulses from the output of the first rectangular pulse generator 1, increases progressively, which leads to a stepwise change in the voltage at the output of the digital-to-analog converter 7 and, as a result current of the controlled current source 8. The formation of a stepwise increasing compensating field N _to (Fig. 2). At the same time, the code of the second pulse counter 16 increases. The EMF induced in the output winding 3 of the flux gate 2 during the magnetization reversal of its core (U3 in Fig. 2) is proportional to the rate of change of induction in the core of the flux gate 2. The core of the flux gate 2 is made of permalloy with a hysteresis loop with a square coefficient close to unity, i.e. the rate of change of induction in the region from -Bm-Br is practically zero. Therefore, the output signal U3 in the portion t0-t1 is equal to zero. From time t1 to time t2, each step of the compensating field H _k will correspond to an EMF pulse induced in the output winding 3 of the flux gate 2, since the core induction will vary from -Br to Br. These pulses lead to the triggering of threshold block 4. The first pulse from the output of threshold block 4, arriving at the second input of the first RS-trigger 11, causes a signal at its output to allow 15 pulses from the output of the first square-wave generator to pass through the second logical element AND. However, they do not enter it because the same pulse from the output of the threshold block 4, arriving at the third input of the second logical element And 15, prevents this. This situation continues until voltage pulses occur at the output of threshold block 4, i.e. during the time t1-t2. In addition, in the same period of time, the signal from the threshold block 4 prevents the passage of pulses from the output of the first rectangular pulse generator 1 through the first logic element AND 5 to the first input of the second pulse counter 16 through the OR gate 17. During the time interval t1-t2 by the first input of the second pulse counter 16 receives pulses from the output of the threshold unit 4, passing through the T-trigger 14 (U14 in Fig. 2) and the logic element OR 17, which leads to the calculation of every second pulse during this time. At time t2, the induction of pulses in the output coil 3 of the flux gate 2 will stop, which means that they will disappear at the output of the threshold unit 4, so at time t2, the pulse from the output of the first pulse generator 1 through the second logic element And 15 will lead the first 11 and second 12 RS- triggers in the initial state. The change in the codes of the first 6 and second 16 pulse counters and the flow of current through the key 9 along the excitation winding 10 of the flux-gate 2 will stop. The threshold unit 4 provides the symmetry of the occurrence and disappearance of pulses (U _then Fig. 2) relative to the zero point on the coordinate axes B (H).

In view of the fact that the code of the second pulse counter 16 will be equal to the sum of the steps of the compensating field for the time interval t0-t1 and half the sum of the steps of this field during the time interval t1-t2, and the hysteresis loop of the core of the flux-gate 2 is symmetrical with respect to the coordinate center 0, this the code will be proportional to H _meas .

The blocks included in the digital device for measuring the magnetic field can be performed, for example:
first and second rectangular pulse generator, threshold block, first, second and third logical elements AND, first and second pulse counter, digital-to-analog converter, key, first and second RS-triggers, T-trigger, OR logic element, as described in ( Yakubovsky S.V., Barkanov N.A., Kudryashov B.P. Analog and Digital Integrated Circuits. - M.: Sov. Radio, 1979. - 336 p.);
a flux gate, as two windings on a core made of permalloy with a hysteresis loop with a rectangular coefficient close to unity;
controlled current source as an amplifier with current feedback according to Falkenberry L. Application of operational amplifiers and linear ICs: Transl. from Eng. - M .: Mir, 1985 .-- 572 p.

 Experimental studies of the layout of the inventive digital device for measuring magnetic field strength showed that, compared with a device of a similar purpose (prototype), the inventive device provides improved measurement accuracy by eliminating the elements of analog signal processing.

Claims (1)

 A digital device for measuring the magnetic field strength, containing the first generator of rectangular pulses, a flux gate with a core made of permalloy with a hysteresis loop with a square coefficient close to unity, to the output winding of which a threshold block is connected, the output of the threshold block is connected to the first input of the first logic element And, connected in series with the first pulse counter, a digital-to-analog converter, a controlled current source, a key and an excitation winding of a flux gate, the second input of the first logical element And is connected to the output of the first rectangular pulse generator, characterized in that it is equipped with a first and second RS-trigger, a second rectangular pulse generator, a T-trigger, a second logical element And, a second pulse counter, an OR logical element and a third a logical element And, and the output of the second rectangular pulse generator is connected to the first input of the second RS-trigger and the second inputs of the first and second pulse counters, the second input of the second RS-trigger and the first the input of the first RS-trigger is connected to the output of the second logical element And, the first, second and third inputs of which are connected respectively to the outputs of the first RS-trigger, the first square-wave generator and threshold block, the input of the T-trigger and the second input of the first RS-trigger are connected to the output of the threshold block, the first and second inputs of the OR gate are connected to the outputs of the T-trigger and the first logical gate And, the output of the OR gate is connected to the first input of the second pulse counter, the output of the second RS-trigger and connected to the second input of the key, to the third input of the first logical element And and the first input of the third logical element And, the second input of the third logical element And is connected to the output of the first rectangular pulse generator, the output of the third logical element And is connected to the first input of the first pulse counter.

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