JPS631254Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a magnetic property detection circuit that measures the magnetic property of a magnetic material in response to an alternating current signal.

As is well known, various devices have been developed for measuring the magnetic properties of magnetic materials in response to alternating current signals, that is, the B-H characteristics or the M-H characteristics. Figure 1 shows the configuration of this type of device, where 11 is a sine wave oscillator, 12 is a constant current amplifier, L _D is a terminal 13,
A sample to be measured, such as a coil with a magnetic core, is connected to terminal 14, and reference objects, such as an air-core coil and a _resistor , are connected to terminals 15 _and 16, respectively.
R _D is a resistance for exciting current detection. Also, R ₁ , R ₂
~ _R9 are connected to the operational amplifiers _O1 , _O2 , _O3, respectively, and the first, second, and third differential amplifiers _D1 , _D2 , _D3
The resistors RV ₁ , RV ₂ , and RV ₃ are variable resistances for adjusting the balance of the first, second, and third differential amplifiers D ₁ , D ₂ , and D _{3 ,} respectively. The amplifier D ₁ takes out the voltage across the sample L _D to be measured, and the second differential amplifier D ₂ takes out the voltage across the reference object R _s or L _s . Furthermore, the third differential amplifier D ₃ extracts the differential voltage between the outputs _of the first and second differential amplifiers D _{1 and} D ₂ . The output signal of the third differential amplifier _D3 is supplied to an integrator 17, which outputs a signal corresponding to the magnetic flux density B or the magnetization M of the magnetic core according to the reference object to an output terminal 18. Ru. Further, 19 is a current-voltage conversion amplifier connected to both ends of the current detection resistor R _D , and this amplifier 1
9 outputs a signal corresponding to the magnetizing force H to the output terminal 20.
is output to. Note that 21 is a ground terminal.

In the above configuration, for example, the terminals 13, 14, 1
Assuming that voltages V ₁ , V ₂ , V ₃ , and V ₄ are generated at D 5 and 16, respectively, the output voltage V ₅ of the first differential amplifier D ₁ is V ₅ = (R ₁ + R ₂ /R ₃ + RV ₁ ) RV ₁ /R ₁ V ₂ -R ₂ /R ₁ V ₁ , and assuming that R ₁ , R ₂ , R ₃ , and RV ₁ are the same resistance value R, the previous equation becomes V ₅ = (R + R / R+R) R/RV ₂ −R/RV ₁ =V ₂ −V ₁
...(1) becomes. Also, the output voltage of the second differential amplifier D ₂
V ₆ becomes V ₆ = (R ₄ + R ₆ / R ₅ + RV ₂ ) RV ₂ / R ₄ V ₄ − R ₆ / R ₄ V ₃ , and R ₄ , R ₅ , R ₆ , and RV ₂ are connected to the same resistance. Assuming the value R, the previous equation is V ₆ = (R + R / R + R) R / RV ₄ - R / RV ₃ = V ₄ - V ₃
...(2) becomes. Furthermore, _the output voltage _V7 of the third differential amplifier _D3 is _V7 =( _R7 + _R8 / _R9 + _RV3 ) _{RV3 /R7V6-R8 / R7V5 ,} and _R7 , Assuming that R ₈ , R ₉ , and RV ₃ have the same resistance value R, the previous formula is V ₇ = (R + R / R + R) R / RV ₆ - R / RV ₅ = V ₆ - V ₅ ...
…(3) becomes. Here, by substituting equations (1) and (2) above into equation (3), we get V ₇ = (V ₄ − V ₃ ) − (V ₂ − V ₁ ), and since V ₃ = V ₂ , this is expressed as V ₂ , the previous equation becomes V ₇ =V ₄ −2V ₂ +V ₁ . That is, the output voltage of the third differential amplifier _D3
V ₇ is the voltage between terminals 13 and 14 and terminals 15 and 16
It can be seen that the voltage difference between the two is taken.
However, the above equation is based on a theoretical value, and in reality, measurement errors occur because the impedance of the object to be measured is taken into account.

Therefore, for example, if the impedance seen from the first differential amplifier D ₁ at the terminal 13 is r ₁ and the terminals 14, 15, and 16 are similarly set to r ₂ , r ₃ , and r ₄ , the first difference The output voltage V ₅ of the dynamic amplifier D ₁ is V ₅ = {(R ₁ + r ₁ ) + R ₂ / (R ₃ + r ₂ ) + RV ₁ } (RV ₁ / R ₁ + r ₁ ) V ₂ − (R ₂ / R ₁ +r ₁ )V ₁ , and assuming that R ₁ , R ₂ , R ₃ , and RV ₁ have the same resistance value R, the previous equation becomes V ₅ = (R+r ₁ +R/R+r ₂ +R) (R/R+r ₁ )V ₂ -(R/R+ _V1 ) _V1 =(2R+ _r1 /2R+ _r2 )(R/R+ _r1 ) _V2- (R/R+ _V1 ) _V1 ...(4). Similarly, the output voltage of the second differential amplifier D ₂
V ₆ becomes V ₆ = {(R ₄ + r ₃ ) + R ₆ / (R ₅ + r ₄ ) + RV ₂ } (RV ₂ / R ₄ + r ₃ ) V ₄ − (R ₆ / R ₄ + r ₃ ) V ₃ , Assuming that R ₄ , R ₅ , R ₆ , and RV ₂ have the same resistance value R, the previous formula is V ₆ = (R + r ₃ + R/R + r ₄ + R) (R/R + r ₃ ) V ₄ - (R/R + r ₃ ) V ₃ = (2R + r ₃ / 2R + r ₄ ) (R/R + r ₃ ) V ₄ - (R/R
+r ₃ )V ₃ ...(5). Also, the output voltage of the third differential amplifier _A3
V ₇ is determined by using equations (4) and (5) from the relationship of equation (3) above, V ₇ = {(2R+r ₃ /2R+r ₄ )(R/R+r ₃ )V ₄ −(R/R+r ₃ )V ₃ } −{(2R+r ₁ /2R+r ₂ )(R/R+r ₁ )V ₂ −(R/
R+r ₁ ) V ₁ }. Here, since V ₃ = V ₂ and r ₃ = r ₂ ,
If we unify this into V ₂ and r ₂ , the previous equation becomes V ₇ = (2R + r ₂ / 2R + r ₄ ) (R/R + r ₂ ) V ₄ - (R/R
+r ₂ )V ₂ −(2R+r ₁ /2R+r ₂ )(R/R+r ₁ )V ₂ +(R/R
+r ₁ ) V ₁ . As is clear from this equation, since r ₁ , r ₂ , and r ₃ vary depending on the sample, terminals 13, 14,
It is difficult to accurately measure the voltage between terminals 15 and 16. Therefore, the variable resistors RV ₁ to _{RV 3} are adjusted to apparently eliminate the influence of the sample. However, performing this adjustment every time the sample is changed requires a large amount of man-hours, and even after adjustment, the active impedance of the sample changes, resulting in errors.

This idea was made based on the above circumstances, and it separates the constant current amplifier that supplies the excitation current from the ground line of the oscillator, and connects the voltage of the sample and reference object to which the excitation current is supplied to the first The configuration and adjustment are extremely simple, as the output voltages of the first and second amplifiers are combined and integrated, and the excitation current is detected by the third amplifier. It is an object of the present invention to provide a magnetic property detection circuit that can measure the B-H characteristic or the M-H characteristic of a magnetic material with high precision.

An embodiment of this invention will be described below with reference to the drawings.

In FIG. 2, numeral 31 is, for example, a sine wave oscillator capable of generating any frequency. This oscillator 31
One output end is connected to one end of the primary winding of the isolated transformer 32, and the other output end is grounded together with the other end of the primary winding of the transformer 32. The secondary winding of the isolation transformer 32 is connected to an input terminal and a ground terminal of an isolated constant current amplifier 33. This constant current amplifier 33
The output end of is connected to terminal 35 of terminals 35 and 36 to which a magnetic core coil 34 of a sample to be measured, such as a magnetic head, is connected. The terminal 36 is connected to the terminal 39 of the terminals 39 and 40 to which a reference resistor 37 equal to the DC resistance of the sample to be measured or a reference air-core coil 38 having the same shape and number of turns as the sample is connected. The reference resistor 37 is used when measuring the B-H characteristic of the sample to be measured.
Connected to cancel the DC resistance of the sample to be measured,
The air-core coil 38 is connected to cancel the inductance of the sample to be measured when measuring the MH characteristic of the sample to be measured.

The terminal 40 is, for example, a through-type current transformer 4 whose one end is connected to the terminal 41 and the other end is grounded.
2 and is grounded. Also,
A grounding end of the constant current amplifier 33 is connected to a terminal 43, and this terminal 43 is grounded via an excitation current detection resistor 44. Therefore, constant current amplifier 33 is separated from the ground line of oscillator 31 by resistor 44.

On the other hand, the input terminal of a first amplifier 45, which is a phase inversion amplifier, for example, is connected to the terminal 35. Further, a second amplifier 46 is connected to the terminal 39.
is connected to the input terminal of this second amplifier 4.
6 and the output signal of the first amplifier 45 have a phase difference of 180°. The first and second amplifiers 4
5 and 46 are combined via a balance resistor 47 and a balance adjustment variable resistor 48, respectively, and are connected to an output terminal 49 and an input terminal of an integrator 50. When a reference resistor is connected to the output terminal 49, the differential dB/dt of the magnetic flux density B of the magnetic core in the sample to be measured with respect to time t is output, and when an air-core coil for reference is connected, the differential dB/dt of the magnetic flux density B of the magnetic core in the sample to be measured is output. Differentiation of magnetization M with respect to time t at
dM/dt is output.

Further, the integrator 50 integrates the differential output and outputs a voltage proportional to the magnetic flux density B or magnetization M, and its output terminal is connected to an output terminal 51. Further, the input terminal of a third amplifier 52 is connected to the terminal 41. This amplifier 52
is composed of, for example, a current-voltage conversion amplifier, and outputs a voltage proportional to the magnetizing force H from the excitation current detected by the current transformer 42,
This output end is connected to an output terminal 53. Further, the first, second, and third amplifiers 45, 46,
52 and the ground terminal of integrator 50 are each connected to output terminal 54.

The operation in the above configuration will be explained. For example, the voltages at terminals 35, 36, 39, and 40 are V ₁ ,
V ₂ , V ₃ , V ₄ and the potential difference between V ₁ and V ₂ as V ₅ ,
When the potential difference between V ₃ and V ₄ is V ₆ , V ₂ −V ₁ =V ₅ and V ₄ −V ₃ =V ₆ hold. Here, since V ₆ −V ₅ =V ₄ −V ₃ −V ₂ +V ₁ , and V ₂ =V ₃ and V ₄ =0, −2V ₃ +V ₁ =V ₆ −V ₅ ……(6 ) must hold true.

On the other hand, if the output voltage of the first amplifier 45 is V ₇ , the output voltage of the second amplifier 46 is V ₈ , and the gain of the second amplifier 46 is twice that of the first amplifier 45, then V ₇ = V ₄ −V ₁ (because V ₄ =0) V ₇ =V ₁ V ₈ =2(V ₃ −V ₄ )(because V ₄ =0) V ₈ =2V ₃ . Further, if the combined output voltage of the balance resistor 47 and the balance adjustment variable resistor 48 is _V9 , and it is assumed that both are balanced, then _V9 = _2V3 - _V1 (7). Now, comparing the above equations (6) and (7), we get
It can be seen that the absolute values of both equations are the same, only the signs are reversed. Therefore, by finding the combined voltage (differential pressure) of the first and second amplifiers 45 and 46, the magnetic flux density B or magnetization M can be obtained, and the third
The amplifier 52 generates a magnetizing force H proportional to the excitation current.
By determining the B-H characteristic or M-
H characteristics can be measured.

In addition, if the characteristics of the sample to be measured and the reference coil 38 do not match and deviate at a ratio of 1:N, if NV ₆ −V ₅ =NV ₂ −V ₁ , then the balance resistor 47 and the balance adjustment variable If the ratio of the resistor 48 is adjusted to 1/N, V ₇ +V ₈ /N=V ₉ , and since V ₉ =V ₂ /N-V ₁ , the deviation by N times becomes 1/N at the output V ₈ . It becomes N times larger and can be easily corrected. Therefore, if the difference in conditions between the sample to be measured and the reference object is within the allowable range, adjustment can be easily performed and errors can be reduced.

According to the above embodiment, the constant current amplifier 33 is separated from the ground line of the oscillator 31 using the isolation transformer 32 and the current detection resistor 44, and the terminal 40
is grounded. Therefore, the terminal voltages of the sample connection terminal to be measured and the reference connection terminal can be detected using the ground level as a reference by the first and second amplifiers 45 and 46, without using a differential amplifier.
Both terminal voltages can be detected accurately and the configuration can be simplified.

Furthermore, since no differential amplifier is used, no complicated adjustment is required, and measurement can be simplified.
Moreover, since the influence of the impedance of the sample to be measured and the reference object can be removed, highly accurate measurement is possible.

Note that this invention is not limited to the above embodiment; for example, if a constant current amplifier 33 with low noise is used, the current transformer 42 is unnecessary; in this case, the input terminal of the third amplifier 52 is If connected to the terminal 43, the amount of change in current can be taken out.

Of course, various other modifications can be made without changing the gist of the invention.

As described in detail above, according to this invention, it is possible to provide a magnetic property detection circuit which is extremely simple in configuration and adjustment and is capable of measuring the B-H characteristic or M-H characteristic of a magnetic material with high accuracy.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the basic circuit configuration of a magnetic property measuring device, and FIG. 2 is a circuit diagram showing an example of the magnetic property detection circuit according to the invention. 31... Sine wave oscillator, 32... Isolated transformer, 33... Constant current amplifier, 34... Sample to be measured, 37, 38... Reference object, 45, 46, 5
2...first, second, and third amplifiers, 50...integrator.

Claims (1)

[Scope of utility model registration request] A sine wave oscillator capable of generating any frequency, an isolation transformer to which the output signal of this sine wave oscillator is supplied, and a constant current constant for the output of the sine wave oscillator supplied via this isolation transformer. A test sample consisting of a current amplifier, a resistor that separates the input voltage of the constant current amplifier from the ground line, a magnetic material to which the output current of the constant current amplifier is supplied, and a coil wound around the magnetic material is connected. a reference connection terminal connected between the sample-to-be-measured connection terminal and ground to which a resistor or coil corresponding to the sample to be measured is connected, and a connection terminal between the sample-to-be-measured connection terminal and ground. a first amplifier provided between the reference connection terminal and ground, a second amplifier having a phase different from that of the first amplifier, and a combined output signal of the first and second amplifiers. an integrator that outputs a signal corresponding to the magnetic flux density B of the sample to be measured and the magnetization M of the magnetic core according to the resistor or coil connected to the reference connection terminal; A magnetic property detection circuit comprising: a detector for detecting a current flowing in a series circuit of connecting terminals; and a third amplifier for outputting a signal corresponding to a magnetizing force H from the output of the detector.