JP4369909B2 - Magnetic property measuring method and measuring instrument - Google Patents

Description

  The present invention relates to a magnetic property measuring method and a measuring instrument for measuring a magnetic property of a magnetic material sample using a detection coil, and in particular, a response signal corresponding to a change in magnetization of a magnetic material sample detected by the detection coil exhibits a damped vibration. The present invention relates to a method for correcting a response signal when accompanied.

  A detection coil is generally used to detect the magnetization of the magnetic material. When the detection coil is arranged so that the magnetic flux inside the detection coil changes due to a change in magnetization or position of the magnetic material, an electromotive force proportional to the change in magnetic flux is generated in the detection coil. This electromotive force is output from both ends of the detection coil as a response signal corresponding to the change in magnetization of the magnetic sample. In the present application, in the following description, the output signal of the detection coil corresponding to the magnetization change of the magnetic sample is referred to as a response signal. By detecting the response signal and performing signal processing such as integration, a magnetization signal can be obtained.

  Hereinafter, an outline of an AC magnetization detection device using a detection coil, which is considered to be the most common among conventional magnetization detection devices, will be described with reference to FIG. The AC magnetization detection apparatus shown in FIG. 13 includes magnetic field coils 1a and 1b for applying a measurement magnetic field to a magnetic sample 5 as a sample to be measured, an excitation power source 2 for supplying an excitation current to the magnetic field coils 1a and 1b, and measurement thereof. A detection coil 3 for detecting the magnetization of the magnetic sample 5 that changes with the magnetic field, a response signal output from the detection coil 3 is integrated, an integrator 4 that outputs the integrated signal as a magnetization proportional voltage, and a measurement magnetic field is detected. A measurement magnetic field detection unit 6 that outputs a magnetic field proportional voltage, and a display unit 7 that displays the magnetization proportional voltage and the magnetic field proportional voltage as an XY graph. As an example, the measurement magnetic field detection unit 6 may measure the excitation current flowing in the magnetic field coils 1a and 1b and convert it into a magnetic field proportional voltage.

When an alternating current is passed through the magnetic field coils 1 a and 1 b by the excitation power supply 2, a measurement magnetic field is applied to the magnetic material sample 5. Following the change in the measurement magnetic field, the magnetization of the magnetic sample 5 changes, the amount of magnetic flux passing through the detection coil 3 changes, an electromotive force is generated in the detection coil 3, and response signals are output from both ends of the detection coil 3. The When this response signal is taken in and integrated by the integrator 4, a magnetization proportional voltage can be obtained. If the magnetic field proportional voltage obtained by the measurement magnetic field detection unit 6 is plotted on the horizontal axis, the magnetization proportional voltage obtained by the integrator 4 is plotted on the vertical axis, and output to the display unit 7 as an XY graph, the magnetic characteristics of the magnetic material are expressed. A hysteresis loop (MH loop) is displayed.

Here, since the magnetic flux penetrating the detection coil 3 is a superposition of the component caused by the magnetization of the magnetic sample 5 and the component caused by the measurement magnetic field, a device for extracting only the component caused by the magnetization is necessary. It is. As an example of the device, as shown in FIG. 14, a method of canceling a component caused by a measurement magnetic field by connecting a compensation coil 8 having a reverse winding, the same number of turns, and the same cross-sectional area to the detection coil 3 in series with the detection coil 3. There is.

  In the conventional magnetic property measuring instrument described above, the problem is that the detection coil 3 has a certain resonance frequency. This is because if the number of turns of the detection coil 3 is increased in order to increase the detection sensitivity, the stray capacitance between the windings cannot be ignored, and resonance occurs at a certain frequency with the inductance of the detection coil 3 and the stray capacitance between the windings. by. As a result, especially when the change in magnetic flux in the detection coil 3 has a frequency component equal to or higher than the resonance frequency, the response signal of the detection coil 3 often includes a damped oscillation waveform. FIG. 15 shows the measurement result (hysteresis loop) when this vibration waveform occurs. As shown in FIG. 15, when the response signal from the detection coil 3 includes a damped vibration waveform, the measurement result is not reliable and is a problem in accurate magnetic characteristic measurement.

  Therefore, the present invention corrects the influence of stray capacitance on a response signal measured using a detection coil in which stray capacitance between windings is a problem, and can measure more accurate magnetic characteristics. The purpose is to provide.

According to a first aspect of the present invention, there is provided a magnetic characteristic measuring method comprising: an impulse response measuring step for obtaining an impulse response of a detection coil for detecting a magnetic characteristic of a magnetic sample; a magnetic field applying step for applying a measurement magnetic field to the magnetic sample; A detection step of detecting a response signal corresponding to a change in magnetization of the magnetic sample by a detection coil; and a correction step of correcting the response signal obtained in the detection step by deconvolution with an impulse response.
According to this method, it is possible to appropriately correct the output of the detection coil affected by the stray capacitance and to measure more correct magnetic characteristics.
In the impulse response measurement step of the magnetic characteristic measuring method according to claim 2, the impulse response is obtained from the response waveform of the detection coil when a step magnetic field is applied to the detection coil.
In the impulse response measurement step of the magnetic characteristic measuring method according to claim 3, the impulse response is obtained from the response waveform of the detection coil when the impulse current is injected into the detection coil.
According to these methods, the impulse response of the detection coil necessary for correcting the response signal can be accurately obtained.
In the magnetic characteristic measuring method according to the fourth aspect, the impulse response is approximated by an approximate impulse response including a product of an amplitude term, an exponential function term, a cosine function term, and a unit step function term.
In the magnetic characteristic measuring method according to the fifth aspect, the approximate impulse response is obtained from the response signal detected in the detection step.
In the magnetic characteristic measuring method according to the sixth aspect, the approximate impulse response is obtained from the frequency analysis spectrum of the response signal.
In the magnetic characteristic measuring method according to the seventh aspect, the approximate impulse response is obtained from the damped oscillation waveform representing the response signal on the time axis.
According to these methods, the impulse response of the detection coil is approximated by a relatively simple expression having an attenuation amplitude, and the adjustment parameter of the approximate expression can be obtained from the frequency analysis spectrum of the actually measured response pulse or the attenuation vibration waveform. I can do it. As a result, an approximate impulse response that can be widely applied to a normal detection coil can be obtained.
The magnetic property measuring instrument according to claim 10 is a magnetic field coil for applying a measurement magnetic field to a magnetic sample, an excitation power source for passing an excitation current for generating the measurement magnetic field to the magnetic field coil, a measurement magnetic field, and a magnetic field proportional voltage. A magnetic field detector that outputs, a detection coil that outputs a response signal corresponding to the change in magnetization of the magnetic sample with respect to the measurement magnetic field, and a response signal that is corrected by deconvolution with the impulse response of the detection coil, and a correction signal is output A correction unit that integrates the correction signal and outputs a magnetization proportional voltage proportional to the amount of magnetization of the magnetic sample, and a magnetic field sample M-H using the magnetic field proportional voltage and the magnetization proportional voltage. A display unit for displaying a loop.
According to this configuration, it is possible to provide a magnetic characteristic measuring instrument that can appropriately correct the response signal of the detection coil that is affected by the stray capacitance and measure more correct magnetic characteristics.

  According to the present invention, a magnetic characteristic measuring method capable of correcting the influence of stray capacitance and measuring more accurate magnetic characteristics with respect to a response signal measured using a detection coil in which stray capacitance between windings is a problem. And a measuring instrument can be provided.

(Deconvolution method)

Prior to the description of a specific embodiment, a method for deconvolution of the output signal of the detection coil, which is the key of the present invention, will be briefly described.

When an impulse is input to the detection coil, the response output of the detection coil includes a damped vibration waveform due to the influence of the distributed capacity. In the present application, the response output of the detection coil that takes into account the influence of the distributed capacitance on the impulse input is referred to as an impulse response. This impulse response generally has a waveform unique to each detection coil.

Here, an ideal detection coil that is not affected by the distributed capacitance is assumed. This ideal detection coil is referred to as an ideal detection coil in the present application. Since there is no influence of the distributed capacity, the response signal output from the ideal detection coil can be said to be a “true” response signal that does not include a damped oscillation waveform. The subject of the present invention is to approximately estimate a response signal that does not include a damped vibration waveform when the coil is an ideal detection coil from a response signal that includes a damped vibration waveform output from an actual detection coil. There is.

Here, if the impulse response is h (t), the response signal of the ideal detection coil due to actual magnetization reversal is x (t), and the response signal of the actual detection coil due to actual magnetization reversal is y (t), these A convolution integral of “Equation 1” is established between the response signals. The symbol “*” appearing in the formula of “Equation 1” is an arithmetic symbol representing convolution integration.

In general, in numerical analysis, it is easier to use a discrete function rather than a continuous function. Therefore, “Expression 1” is expressed by a discrete function. If the sampling period in the discrete system is T, t = nT, and the continuous functions h (t), y (t), x (t) are the discrete system functions h (n), y (n), x (n). Can be replaced. Therefore, if “Equation 1” is expressed by a discrete function, the convolution sum of “Equation 2” is established.

Here, the z transformation of each term of “Equation 2” is Y (z), H (z), and X (z). The definition of z-transform is as “Equation 3”. z is an operator used in a discrete transfer function. By using this z transformation, numerical analysis of a transient response in a discrete system is facilitated.

When “Equation 2” is z-transformed and arranged using “Equation 3”, the state equation “Equation 4” of the transfer functions Y (z), H (z), and X (z) can be obtained.

Here, an inverse function of the impulse response H (z) is described by a general formula as shown in “Formula 5”.

By substituting this into “Equation 4” and arranging it, the relational expression “Equation 6” between X (z) and Y (z) is obtained.

When “Equation 6” is inversely z-transformed and represented by a discrete system function again, a difference equation “Equation 7” representing the inverse circuit of the detection coil is obtained. The constant group aj, bi of “Equation 7” can be determined by measuring the impulse response h (n) and z-transforming it. By substituting the measured response signal y (k) into “Equation 7”, the response signal x (k) of the ideal detection coil, that is, the response signal of the detection coil without the influence of stray capacitance can be obtained.

(First embodiment)

  FIG. 1 is a block diagram of a magnetic property measuring instrument according to the first embodiment of the present invention. The magnetic property measuring instrument of this embodiment detects magnetic field coils 11a and 11b for applying a measurement magnetic field to the magnetic material sample 15, an excitation power source 12 for flowing an excitation current through the magnetic field coils 11a and 11b, a measurement magnetic field, A magnetic field detection unit 16 that outputs a magnetic field proportional voltage, a detection coil 13 that outputs a response signal corresponding to a change in magnetization of the magnetic sample 15 with respect to the measurement magnetic field, and a response signal generated in the detection coil is opposite to the impulse response of the detection coil. A correction unit 19 that corrects by convolution and outputs a correction signal, an integrator 14 that integrates the correction signal and outputs a magnetization proportional voltage proportional to the amount of magnetization of the magnetic sample 15, a magnetic field proportional voltage and a magnetization proportional voltage And a display unit 17 for displaying the MH loop of the magnetic material sample 15.

The excitation power supply 12 and the magnetic field coils 11a and 11b are connected so that the excitation current from the excitation power supply 12 is supplied to the magnetic field coils 11a and 11b. The detection coil 13 is disposed in a region where the measurement magnetic field generated by the magnetic field coils 11a and 11b is substantially uniform (within a uniform magnetic field range). Further, the magnetic sample 15 as the object to be measured is arranged in a uniform magnetic field range and at a position where the magnetic flux penetrating the detection coil 13 is changed by the magnetization change of the sample. The response signal output from the detection coil 13 is processed by the correction unit 19 and the integrator 14 and then output to the display unit 17, and the output from the magnetic field detection unit 16 is also sent to the display unit. When the signal levels of the magnetic field proportional voltage and the magnetization proportional voltage are low, signal amplifiers such as preamplifiers are appropriately inserted into these signal lines.

As a method for detecting the measurement magnetic field by the magnetic field detection unit 16, there is a method for directly detecting the measurement magnetic field with a gauss meter, a flux coil, or the like. In addition, since the measurement magnetic field generated by the magnetic field coils 11a and 11b is proportional to the excitation current that is passed through the magnetic field coils 11a and 11b, the measurement magnetic field is indirectly estimated by detecting the excitation current. There is also a method. For detection of the excitation current, a shunt resistor or a current transformer connected in series with the magnetic field coils 11a and 11b is used.

The operation of the magnetic property measuring instrument of this embodiment will be described according to the flowchart shown in FIG.
(Impulse response measurement step S1) Impulse is input to the detection coil 13, the impulse response of the detection coil 13 with respect to the input is measured, and constant groups ai and bj of the difference equation “Equation 7” are calculated from the measurement result, The difference equation “Formula 7” is formulated.

Here, a method for obtaining the constant group of the difference equation “Equation 7” from the impulse response h (n) will be described below. The impulse response measured in the impulse response measurement step S1 can be written down in a numerical sequence represented by “Equation 8” by expressing it as a discrete system function. Here, M is the number of samples until the impulse response, which is a damped oscillation waveform, converges to almost zero.

“Equation 9” is obtained by z-transforming “Equation 8”.

Here, the inverse function of “Equation 9” is “Equation 10”.

When the correspondence relationship between the mathematical expressions of “Equation 6” and “Equation 7” is adapted to “Equation 10”, a differential equation “Equation 11” for correction is obtained. In the correction step S4 to be described later, the response signal is corrected by deconvolution using the difference equation “Equation 11”.

Note that the differential equation “Equation 11” obtained once can be used for correction at the time of subsequent measurement as a regular correction expression, except when the detection coil 13 is replaced or deformed. That is, the impulse response measurement step S1 does not necessarily need to be performed for each subsequent measurement because once the difference equation “Equation 11” is obtained, the obtained correction equation may be used. .

In the present application, the process from measuring the impulse response described above to determining the differential equation for deconvolution is referred to as an impulse response measurement step.

  (Magnetic field application step S2) A measurement magnetic field is applied to the magnetic sample 15. After the magnetic material sample 15 is set, an excitation current is applied to the magnetic field coils 11a and 11b from the excitation power source 12 to generate a measurement magnetic field. The excitation current generally uses an alternating current having a sinusoidal waveform. Further, the measurement magnetic field is detected, and a magnetic field proportional voltage proportional to the measurement magnetic field is output to the display unit. This series of processing steps relating to the measurement magnetic field application is referred to as a magnetic field application step in the present application.

(Detection step S3) A response signal output from the detection coil 13 corresponding to the change in magnetization of the magnetic sample 15 is detected. Due to the measurement magnetic field applied to the magnetic sample 15 in the magnetic field application step S2, the internal magnetization of the magnetic sample 15 changes, and accordingly, the amount of magnetic flux inside the detection coil 13 changes, and an electromotive force is generated in the detection coil 13. The response signal corresponding to the magnetization change of the magnetic sample 15 is generated. In general, when the magnetic material sample 15 is a thin film or the like, the response signal is very weak, and therefore, it is necessary to amplify the signal with an amplifier such as an operational amplifier. This series of processing steps for detecting the response signal of the detection coil 13 is referred to as a detection step in the present application.

(Correction step S4) The response signal of the detection coil 13 obtained in the detection step S3 is corrected. The response signal of the detection coil 13 includes a damped vibration waveform due to the influence of the distributed capacity. The response signal is corrected to obtain a response signal that would be obtained when using a detection coil that is not affected by the distributed capacitance. As a correction method, a deconvolution process using the difference equation “Equation 11” obtained in the impulse response measurement step S1 is used.

More specifically, a correction circuit based on the difference equation “Equation 11” is configured to perform deconvolution. That is, FIG. 3 is a block diagram of a correction circuit used in the magnetic property measuring instrument of this embodiment. The response signal y (k) input from the input terminal 51 is multiplied by 1 / p0 by the amplifier 52 and sent to the adder 53. Here, p0 is a constant in the difference equation “Equation 11”. The output of the adder 53 is sent to the delay element 54-1. The signal sent to the delay circuit 54-1 is output to the delay circuit 54-2 with a delay of the sampling period T. Since the output signal of the delay circuit 54-1 is delayed by one sampling time (= T) from the output signal x (k) output from the output terminal 56, it can be expressed as x (k-1). As in the case of the delay circuit 54-1, the signal x (k-1) sent to the delay circuit 54-2 is further sent to the next delay circuit with a delay of the sampling period T. k-2). Similarly, the signal passes through M delay circuits, and in the final stage 54-M, a signal x (k−M) with a delay of T × M is output.

The M signals x (k−N) (N is an integer from 1 to M) with a delay output from each delay circuit 54-1 to M are respectively amplifiers 55-N (N is from 1 to M). PN / p0 times. pN (N is an integer from 1 to M) is a constant in the difference equation “Equation 11”. Thereafter, the signals amplified by the amplifier 55 -N are added by the adder 53 and output from the output terminal 56 as the correction signal x (k).

A series of correction processing steps for the response signal is referred to as a correction step in the present application. FIG. 4 shows waveforms before and after applying this correction, and shows the effect of this correction. In FIG. 4, a waveform F is a response signal waveform before correction, and corresponds to y (k) in FIG. It can be seen that a damped oscillation waveform is included due to the influence of the distributed capacity. A waveform G is a response signal waveform (that is, a correction signal waveform) after correction by the correction circuit, and corresponds to x (k) in FIG. The attenuation signal waveform is removed by the action of the correction circuit, and a “true” response waveform is obtained.

(Integration Step S5) The response signal corrected by the correction step, that is, the correction signal is further subjected to integration processing. The integration includes a method using an integrator or a method of performing numerical calculation using a computer or the like as a means to perform integration. The signal obtained by this integration process is output to the display unit as a magnetization proportional voltage that is proportional to the magnetization. This step of integrating the series of correction signals is referred to as an integration step in the present application.
FIG. 5 shows a waveform obtained by this integration process. The waveform H does not include a correction step, that is, a waveform of a magnetization proportional voltage detected by a measurement method based on the prior art. The influence of the damped oscillation waveform included in the response signal also appears in the integrated waveform. A waveform I is a waveform of a magnetization proportional voltage detected by the measurement method based on the present invention. Note that the effect of the damped oscillation waveform as seen in waveform H has been removed.

(Display Step S6) An XY graph is displayed on the display with the magnetization proportional voltage output in the integration step S5 as the vertical axis and the magnetic field proportional voltage output in the magnetic field application step S2 as the horizontal axis. In general, display is performed using a multi-channel oscilloscope or the like. As a display result, an MH loop is obtained. A series of processing steps for displaying the MH loop is referred to as a display step in the present application. Thus, a series of operations of the magnetic property measuring instrument of this embodiment is completed.

(Second embodiment)

The block diagram of the magnetic property measuring instrument and the flowchart of the measurement operation in the second embodiment are the same as those in the first embodiment described above, but in this embodiment, the impulse input method in the impulse response measurement step S1 A method of applying a step magnetic field to the detection coil 13 is used.
The impulse response measurement step S1 of this embodiment will be described more specifically with reference to FIG. A pulse magnetic field generating coil 21 is used as a pulse magnetic field generating coil. In order to suppress the inductance of the pulse magnetic field generating coil 21, the inner diameter is made as small as possible and the number of turns is minimized. If it is difficult to supply current from the current source 22 because the load impedance is low, a resistor or the like is connected in series with the pulse magnetic field generating coil 21 in accordance with the output impedance of the current source 22. The pulse magnetic field generating coil 21 is connected to a current source 22 having good current rising characteristics. In the impulse response measurement step S1, a stepped magnetic field is generated by supplying a stepped current from the current source 22 to the pulse magnetic field generating coil 21. By applying the step magnetic field, an impulse electromotive force is generated in the detection coil 23, and the impulse response can be detected.

(Third embodiment)

The block diagram of the magnetic property measuring instrument and the flowchart of the measurement operation in the third embodiment are the same as those in the first embodiment described above, but in this embodiment, the impulse input method in the impulse response measurement step S1 A method of supplying an impulse current to the detection coil is used.
This will be described more specifically with reference to FIG. A resistor 34 is connected in series to the detection coil 33, and a pulse voltage source 32 is connected in parallel to the resistor 34. In the impulse response measurement step S1, an impulse current is supplied to the detection coil 33 by supplying a pulse voltage from the pulse voltage source 32, and the impulse response at that time is measured. This impulse response is a response including the influence of the stray capacitance of the detection coil 13.

(Fourth embodiment)

The block diagram of the magnetic property measuring instrument and the flowchart of the measurement operation in the fourth embodiment are the same as those of the first embodiment described above, but the flowchart of the measurement operation is different. Below, the difference of this measurement is demonstrated.
In this embodiment, a measurement operation according to the flowchart shown in FIG. 8 is performed.
(Magnetic field application step S11) A measurement magnetic field is applied to the sample. The specific contents of this magnetic field application step S11 are the same as the magnetic field application step S2 described in the first embodiment.
(Detection step S12) A response signal is detected by the detection coil 13. The specific content of this detection step S12 is the same as the detection step S3 described in the first embodiment.
(Impulse response measurement step S13) The major difference between this embodiment and the first embodiment is in the impulse response measurement step S13 described below. In this embodiment, an approximate impulse response is calculated from the response signal detected in the detection step S12 and used for the deconvolution process.

The waveform of the impulse response can be approximated by an approximate expression consisting of the product of the amplitude term, the exponential function term, the cosine function term, and the unit step function term expressed by “Equation 12”. FIG. 9 shows the impulse response waveform and the approximate waveform obtained from “Equation 12” in an overlapping manner. A waveform D is an impulse response obtained by actual measurement, and a waveform E is an approximation of this by “Equation 12”. As shown in this figure, the approximate value of the impulse response waveform can be obtained with high accuracy by using the approximate expression of the impulse response represented by “Equation 12”. In addition, the response signal detected in the detection step S12 includes a damped vibration waveform due to the influence of the distributed capacity, and this damped vibration waveform is close to the impulse response waveform of the detection coil. That is, an approximate impulse response can be obtained by fitting the approximate expression “Equation 12” of the impulse response to the damped oscillation waveform included in the response signal. In the present application, this approximate impulse response is referred to as an approximate impulse response. According to this method, as indicated by “Equation 12”, the impulse response characteristic of the detection coil 13 can be approximately represented by the binary value of the characteristic value ω that determines the period of vibration and α that is the time constant of attenuation. it can. In “Equation 12”, u (n) is a step function (a function where n <0 and u (n) = 0, n> = 0 and u (n) = 1), T is a sampling period of AD conversion, A0 indicates an initial amplitude proportional to the magnitude of the impulse input. In the impulse response measurement step S13, an approximate impulse response is obtained by fitting the response signal detected in the detection step S12 to “Equation 12”, and a difference equation for correction is obtained from the obtained approximate impulse response. The calculation method of this difference equation is described below.

“Expression 13” is obtained by z-transforming the approximate expression “Expression 12” of the impulse response.

The inverse function of “Equation 13” is expressed by “Equation 14”. It should be noted that “Expression 14” is rewritten into an expression corresponding to “Expression 5” by constant definition in order to derive a differential equation later.

Therefore, if the correspondence between the mathematical expressions of “Equation 6” and “Equation 7” is applied to “Equation 14”, a differential equation “Equation 15” for correction is obtained. In a correction step S16 to be described later, the response signal is deconvolved using the difference equation “Equation 15”. The constant group of the difference equation “Equation 15” can be easily calculated from the constants ω and α of the approximate expression “Equation 12” of the impulse response. The difference equation “Equation 15” obtained here can be used for subsequent correction as a commonly used expression except when the detection coil 13 is replaced or deformed. That is, in the impulse response measurement step S13, once the difference equation “Equation 15” is obtained, the obtained difference equation “Equation 15” may be used thereafter. There is no need to do it.

(Magnetic field application step S14) In order to move to actual magnetic measurement, a measurement magnetic field is again applied to the sample. The specific contents of this magnetic field application step S11 are the same as the magnetic field application step S2 described in the first embodiment.
(Detection step S15) A response signal is detected from the detection coil 13. The specific content of this detection step S12 is the same as the detection step S3 described in the first embodiment.

(Correction step S16) The response signal obtained in the detection step S15 is corrected to obtain a response signal equivalent to that obtained when a detection coil not affected by the distributed capacity is used. As a correction method, a deconvolution process using the difference equation “Equation 15” obtained in the impulse response measurement step S13 is used.

More specifically, a correction circuit based on the difference equation “Equation 15” is configured to perform deconvolution. That is, FIG. 10 is a block diagram of a correction circuit used in the magnetic property measuring instrument of this embodiment. The response signal y (k) input from the input terminal 61 is sent to the delay circuit 62-1. The signal sent to the delay circuit 62-1 is output to the delay circuit 62-2 with a delay of the sampling period T. Since the output signal of the delay circuit 62-1 is delayed by one sampling time (= T) from the input signal y (k) input from the output terminal 61, it can be expressed as y (k-1). As in the case of the delay circuit 62-1, the signal y (k−1) sent to the delay circuit 62-2 is transmitted from the delay circuit 62-2 to the signal y (k−) with a delay of the sampling period T. 2). Next, the input signal y (k), the output y (k-1) from the delay circuit, and y (k-2) are respectively a0 times by the amplifiers 63-1, 63-2, 63-3, It is multiplied by a1 and a2. Here, a0, a1, and a2 are constants in the difference equation “Equation 15”. Next, the signals amplified by the amplifiers 63-1, 63-2, and 63-3 are added by the adder 64 and output to the adder 65.

The output from the adder 65 is output to the amplifier 67 by the delay circuit 66 with a delay of the sampling period T. Since the output from the delay circuit 66 is delayed by one sampling time (= T) from the output signal x (k) output from the output terminal 68, it can be expressed as x (k-1). The signal x (k−1) output to the amplifier 67 is multiplied by (−b1) by the amplifier 67 and output to the adder 65. The adder 65 outputs the output from the adder 64, that is, a0 · y (k) + a1 · y (k−1) + a2 · y (k−2), and the output from the amplifier 67, that is, (−b1) · x. Add (k−1) and output from the output terminal 68.

(Integration Step S17) The response signal corrected by the correction step, that is, the correction signal x (k) is further subjected to integration processing. The specific content of the integration step S17 is the same as that of the integration step S5 described in the first embodiment.
(Display Step S18) The magnetization proportional voltage output in the integration step S17 is displayed on the display as an XY graph with the vertical axis representing the magnetization proportional voltage and the horizontal axis representing the magnetic field proportional voltage output in the magnetic field application step S2.

  (Fifth embodiment)

The block diagram of the magnetic property measuring instrument and the flowchart of the measurement operation in the fifth embodiment are the same as those in the fourth embodiment described above, but in this embodiment, from the response signal in the impulse response measurement step S13. As a method for calculating the approximate impulse response, the frequency analysis spectrum of the response signal is used. Hereinafter, this technique will be described with reference to FIG. The response signal 41 is subjected to processing 42 such as FFT to obtain a frequency analysis spectrum 43 of the response signal. Since the response signal 41 includes a damped oscillation waveform due to the stray capacitance of the detection coil 13, the frequency analysis spectrum 43 has a peak at the resonance frequency f of the detection coil 13. This 2π times the resonance frequency f corresponds to ω in the expression “Equation 12” of the approximate impulse response. By this method, one of the two constants ω and α of “Equation 12” is obtained, so that fitting for obtaining an approximate impulse response is facilitated.

(Sixth embodiment)

The block diagram of the magnetic property measuring instrument and the flowchart of the measurement operation in the sixth embodiment are the same as those in the fourth embodiment described above, but in this embodiment, from the response signal in the impulse response measurement step S13. As a method for calculating the approximate impulse response, a damped oscillation waveform representing the response signal on the time axis is used. This technique is shown using FIG. FIG. 12 illustrates a damped oscillation waveform representing the response signal on the time axis. From this damped oscillation waveform, the two constants ω and α of the approximate impulse response “Equation 12” can be obtained. First, the value of ω can be obtained as ω = 2π / 2A from the point where the damped vibration waveform intersects the axis of y = 0, that is, the interval A between the zero cross points. If the peak value of the first peak is B and the peak value of the second peak is C, α = (ln (B) −ln (C)) / 2A, and the transition of the peak of each damped vibration α can be obtained. Here, ln (X) is a natural logarithm function for the variable X. Therefore, it is possible to easily calculate the approximate impulse response from the damped vibration waveform representing the response signal on the time axis.

In the above six embodiments, if software for causing a computer to execute a correction step, an integration step, a display step, and the like is used, it is possible to make the computer carry many functions related to the present invention. In order to execute these steps in a computer, it is necessary to perform AD conversion to convert an analog signal into a digital signal, and to import this into the computer. An AD conversion board that can be built into a computer is used for AD conversion.

In the correction step, by solving the differential equation for deconvolution by numerical calculation by a computer, the same correction as the correction circuit shown in FIGS. 3 and 10 can be performed on the response signal.

In the integration step, an integration result similar to that obtained by integrating with an analog integrator can be obtained by performing numerical integration by a computer on the correction signal obtained in the correction step.

In the display step, the magnetic field proportional voltage and the magnetization proportional voltage captured by the computer by AD conversion may be displayed as an XY graph on a display connected to the computer.

Apparatus configuration of the present invention Measurement operation flow 1 of the present invention Correction circuit obtained from impulse response Effect of correction Integration result after correction Impulse response measurement by step magnetic field Impulse response measurement by impulse current Measurement operation flow 2 of the present invention Approximation of impulse response by "Equation 12" Correction circuit using approximate impulse response Approximate impulse response calculation using frequency analysis spectrum Damped vibration waveform of response signal on time axis Conventional technology Shape of detection coil using compensation coil MH loop with damped vibration waveform

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Magnetic field coil 2 Excitation power supply 3 Detection coil 4 Integrator 5 Magnetic substance sample 6 Measurement magnetic field detection part 7 Display part 8 Compensation coils 11a and 11b Magnetic field coil 12 Excitation power supply 13 Detection coil 14 Integrator 15 Magnetic substance sample 16 Measurement magnetic field Detection unit 17 Display unit 19 Correction unit 21 Pulse magnetic field generating coil 22 Current source 23 Detection coil 31a, 31b Magnetic coil 32 Pulse voltage source 33 Detection coil 34 Resistance 35 Correction unit 41 Response waveform 42 Signal processing 43 such as FFT 43 Frequency analysis spectrum 51 Input Terminal 52 Amplifier 53 Adders 54-1, 54-2, 54-M Delay Circuits 55-1, 55-2, 55-M Delay Circuit 56 Output Terminal 61 Input Terminals 62-1 and 62-2 Delay Circuit 63 -1, 63-2, 63-3 Amplifier 64 Adder 65 Adder 66 Delay circuit 67 Amplifier 68 Output terminal

Claims (11)

An impulse response measurement step for obtaining an impulse response of a detection coil for detecting a magnetic property of the magnetic sample;
A magnetic field applying step for applying a measurement magnetic field to the magnetic sample;
A detection step of detecting, from the detection coil, a response signal corresponding to a change in magnetization of the magnetic sample with respect to the measurement magnetic field;
A magnetic property measurement method comprising: a correction step of correcting the response signal obtained in the detection step by deconvolution with the impulse response. The magnetic characteristic measurement method according to claim 1, wherein in the impulse response measurement step, the impulse response is obtained from a response waveform when a step magnetic field is applied to the detection coil. The magnetic characteristic measurement method according to claim 1, wherein in the impulse response measurement step, the impulse response is obtained from a response waveform when an impulse current is injected into the detection coil. The magnetic characteristic measuring method according to claim 1, wherein the impulse response is approximated by an approximate impulse response including a product of an amplitude term, an exponential function term, a cosine function term, and a unit step function term. The magnetic characteristic measurement method according to claim 4, wherein the approximate impulse response is obtained from the response signal detected in the detection step. The magnetic characteristic measurement method according to claim 5, wherein the approximate impulse response is obtained from a frequency analysis spectrum of the response signal. The magnetic characteristic measurement method according to claim 5, wherein the approximate impulse response is obtained from a damped oscillation waveform representing the response signal on a time axis. The correction step comprises: forming an inverse circuit having a transfer function obtained from z-transform of the impulse response, and correcting the response signal detected in the detection step by passing through the inverse circuit. Magnetic property measurement method. 5. The correction step includes configuring an inverse circuit having a transfer function obtained from z-transform of the approximate impulse response, and correcting the response signal detected in the detection step by passing the inverse circuit. Magnetic property measurement method. A magnetic field coil for applying a measurement magnetic field to a magnetic sample;
An excitation power source for passing an excitation current for generating the measurement magnetic field to the magnetic field coil;
A magnetic field detector that detects the measurement magnetic field and outputs a magnetic field proportional voltage;
A detection coil that outputs a response signal corresponding to a change in magnetization of the magnetic sample with respect to the measurement magnetic field;
A correction unit that corrects the response signal by deconvolution with the impulse response of the detection coil, and outputs a correction signal;
An integrator that integrates the correction signal and outputs a magnetization proportional voltage proportional to the magnetization of the magnetic sample;
A magnetic characteristic measuring instrument comprising: a display unit that displays an MH loop of the magnetic sample using the magnetic field proportional voltage and the magnetization proportional voltage. The magnetic property measuring instrument according to claim 10, wherein at least one of the correction unit and the integration unit is realized by software.