JPH0980134A - Colpitts oscillator type magnetic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve a stable oscillation even if an input voltage fluctuates and amorphous magnetic body impedance scatters in a Colpitts oscillator type magnetic sensor exist. SOLUTION: An inductor Lα 12 is arranged in series with an amorphous magnetic body 1. When the amorphous magnetic body is regarded as an element where a resistor Rw and an inductor Lw are connected in series, the inductor is arranged so that an expression (ωLW+ωLα)<2> >Rw<2> +ARw is satisfied, where A is equal to Rp.hie /Rp+hie , hie is input resistance of a transistor, Rp is all synthetic resistance in parallel with hie , and ω is angular frequency on oscillation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a Colpitts oscillator type magnetic sensor in which an amorphous magnetic substance composed of an amorphous magnetic substance wire, an amorphous magnetic substance ribbon, an amorphous magnetic substance film and the like is inserted in an inductance portion of a Colpitts oscillator. . Here, the Colpitts oscillator is an oscillator of a type in which two capacitors of a parallel tuning circuit are arranged in series to perform voltage division.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional Colpitts oscillator type magnetic sensor. Amorphous magnetic wire 1 is connected in series with power supply Vcc via resistor 2 on one side thereof. Furthermore, the amorphous magnetic wire 1
It is grounded via the capacitor 3 on the other side. Further, the base of the transistor 4 is connected to the amorphous magnetic wire 1. The emitter of the transistor 4 is grounded via the resistor 5, and the collector of the transistor 4 is connected to the power supply Vcc via the resistor 2. A coil 6 that applies a bias magnetic field is wound around the amorphous magnetic wire 1.
Is connected to the power supply Vcc on one side through a resistor 7 for adjusting the magnitude of the bias magnetic field, and is grounded on the other side. A capacitor 8 is connected to the amorphous magnetic wire 1.

The oscillating section is composed of the amorphous magnetic wire 1,
It is composed of a resistor 2, a capacitor 3, a transistor 4, a resistor 5 and a capacitor 8, and an inductance part is composed of an amorphous magnetic wire 1. The oscillating unit is separated from the power supply Vcc by a resistor 2 in an AC manner. The oscillating unit oscillates by resonance with the amorphous magnetic wire 1 and the capacitors 3 and 8 to generate an oscillating signal V _osc . The oscillating signal V _osc enters the direct current conversion (detection / LPF) circuit 9 connected to the oscillating unit, and then is input to the amplifying circuit 10, and the output as the magnetic sensor is transmitted from the terminal 11. The bias magnetic field is applied by the resistor 7 and the coil 6.

[0004]

As described above, the conventional Colpitts oscillator type magnetic sensor has a structure in which the amorphous magnetic wire 1 is inserted into the inductance portion of the Colpitts oscillator. The amorphous magnetic wire 1
It has the property of changing its resistance and inductance depending on the magnetic field. Therefore, the amplitude of the oscillator changes according to the magnetic field. By converting this change in amplitude into a direct current and amplifying it, it can be used as a magnetic sensor.

The conventional Colpitts oscillator type magnetic sensor has a problem that the oscillation is stopped when the input voltage fluctuates by about 0.1 volt. In addition, depending on the amorphous magnetic wire inserted in the inductance portion, it may not oscillate at all. That is, the conventional Colpitts oscillator type magnetic sensor has a problem that stable oscillation cannot be performed.

The present invention has been made in view of the problems of such a conventional Colpitts oscillator type magnetic sensor, and it is stable and stable even if the input voltage fluctuates and the impedance of the amorphous magnetic wire varies. An object is to provide a Colpitts oscillator type magnetic sensor capable of oscillating.

[0007]

In order to achieve this object, a Colpitts oscillator type magnetic sensor according to the present invention is a Colpitts oscillator type magnetic sensor in which an amorphous magnetic material is inserted in an inductance portion of a Colpitts oscillator.
The inductor Lα is arranged in series with the amorphous magnetic material.

Further, in a preferred embodiment of the present invention, when the amorphous magnetic material is regarded as an element in which a resistor Rw and an inductor Lw are connected in series, the following stable oscillation condition expression (1) is satisfied. To the inductor L
It is characterized by arranging α. (ΩLw + ωLα) ² > Rw ² + ARw (1) In the equation (1), A = Rp · h _ie / Rp + h _ie h _ie : input resistance of the transistor Rp: combined resistance in parallel with h _ie ω: during oscillation Is the angular frequency of.

[0009]

FIG. 1 shows an embodiment of a Colpitts oscillator type magnetic sensor according to the present invention. Amorphous magnetic wire 1 is connected in series with power supply Vcc via resistor 2 on one side thereof. Further, the amorphous magnetic wire 1 is grounded on the other side via the inductor Lα12 and the capacitor 3.
Furthermore, the amorphous magnetic wire 1 is connected to the inductor L
It is connected to the base of the transistor 4 via α12. The emitter of the transistor 4 is grounded via the resistor 5, and the collector of the transistor 4 is connected to the power supply Vcc via the resistor 2.

A coil 6 that applies a bias magnetic field is wound around the amorphous magnetic wire 1.
Is connected to the power supply Vcc on one side through a resistor 7 for adjusting the magnitude of the bias magnetic field, and is grounded on the other side. A capacitor 8 is connected to the amorphous magnetic wire 1.

The oscillating portion is composed of the amorphous magnetic wire 1,
The inductor Lα12, the resistor 2, the capacitor 3, the transistor 4, the resistor 5 and the capacitor 8 are configured, and the inductance portion is configured by the amorphous magnetic wire 1 and the inductor Lα12. The oscillating portion oscillates due to the resonance of the amorphous magnetic wire 1, the inductor Lα12 and the capacitors 3 and 8 to generate an oscillating signal of V _osc . This oscillation signal V _osc enters the direct current conversion (detection / LPF) circuit 9 connected to the oscillation unit, and thereafter,
It is input to the amplifier circuit 10 and an output as a magnetic sensor is transmitted from the terminal 11. The bias magnetic field is applied by the resistor 7 and the coil 6.

That is, the Colpitts oscillator type magnetic sensor according to the present embodiment is different from the conventional Colpitts oscillator type magnetic sensor (FIG. 4) in that the inductor Lα12 is inserted in series in the amorphous magnetic wire 1. Is different.

The Colpitts oscillator type magnetic sensor according to the present embodiment configured as described above operates as follows. FIG. 2 shows an external magnetic field-dependent characteristic of the wire impedance obtained by applying a high-frequency current to both ends of the amorphous magnetic wire 1 from a high-frequency power source and applying a magnetic field with a Helmholtz coil in the longitudinal direction of the amorphous magnetic wire 1. It is a graph. As can be seen from FIG. 2, the resistance and reactance of the amorphous magnetic wire 1 change depending on the magnitude of the magnetic field. The composition is (Fe ₆ Co
_{94) 72.5 Si 12. 5 B 15} , the length between the electrodes that are soldered 50 [mu] m, the effective length (amorphous magnetic substance wire diameter)
Was used for the amorphous magnetic wire 1. In addition to the amorphous magnetic wire, an amorphous magnetic ribbon, an amorphous magnetic film, or the like can be used. The size of the amorphous magnetic wire is determined in relation to its impedance.

When the amorphous magnetic wire 1 having the characteristics shown in FIG. 2 was used in the conventional Colpitts oscillator type magnetic sensor shown in FIG. 4, no oscillation occurred regardless of the magnitude of the power supply voltage. The reason for this is as follows.

When the amorphous magnetic wire is regarded as an element in which a resistance and an inductance are connected in series, the stable oscillation condition of the Colpitts oscillator type magnetic sensor shown in FIG. 4 is obtained by the following equation (2). (ΩLw) ² > Rw ² + ARw (2) A = Rp · h _ie / Rp + h _ie h _ie : input resistance of transistor Rp: combined resistance in parallel with h _ie ω: angular frequency at oscillation

Oscillation did not occur at all in the conventional Colpitts oscillator type magnetic sensor because the amorphous magnetic wire having the characteristics shown in FIG. 2 has a resistance larger than the reactance and is represented by the above equation (2). This is because the stable oscillation condition is not satisfied. In the amorphous magnetic wire used in the Colpitts oscillator type magnetic sensor,
In most cases, the resistance component is larger than the reactance, and it is extremely difficult to stably oscillate with the configuration of the Colpitts oscillator type magnetic sensor as shown in FIG.

Therefore, in the Colpitts oscillator type magnetic sensor according to the present invention, as in the embodiment shown in FIG. 1, the inductance Lα12 is inserted in series with the amorphous magnetic wire 1 to increase the reactance. It oscillates stably. The oscillation condition of the Colpitts oscillator type magnetic sensor according to the present invention is expressed by the following equation (1). (ΩLw + ωLα) ² > Rw ² + ARw (1) A = Rp · h _ie / Rp + h _ie h _ie : input resistance of transistor Rp: combined resistance in parallel with h _ie All resistance ω: angular frequency during oscillation

As described above, by properly selecting the value of the inductor Lα12, the stable oscillation condition represented by the above equation (1) can be satisfied, and stable oscillation can be performed.

Examples The results of experiments conducted on the Colpitts oscillator type magnetic sensor according to the present invention will be described below. As the amorphous magnetic wire 1, the composition is (Fe ₆ Co ₉₄ ) _72.5 Si _12.5 B ₁₅ , the magnetostriction constant λ _S = −10 ⁻⁷ , the diameter is 50 μm, and the effective length is 5 m.
m. The coil 6 has 100 turns.
A resistor having a coil diameter of 5 mm was used and the resistance value of the resistor 7 was determined so as to generate a magnetic field of about 3 [Oe]. Resistor 2,
The values of 5 are 300Ω and 22Ω, respectively.
The values of 8 were 150 pF and 51 pF, respectively. As the transistor 4, 2SC2026 which can be used even at a high frequency is used. The inductor Lα12 used is one that satisfies the above-mentioned oscillation condition expression (1).

From the results shown in FIG. 2, the reactance ωLw of the amorphous magnetic wire is 18Ω, the resistance Rw is 40Ω,
If A = 1500Ω, the right side of the oscillation condition expression (1) is 6
It becomes 1600. By making the inductor Lα12 an inductor of 3.5 μH, reactance ωLα = 2π × 14 MHz × 3.5 μH =
It becomes 308Ω, and the left side of the oscillation condition expression (1) = 106276. That is, the value on the left side of the oscillation condition expression (1) becomes larger than the value on the right side, and stable oscillation can be performed. This oscillation signal is input to the DC conversion circuit 9,
By amplifying with the amplifier circuit 10, a sensor output is obtained.

The result of obtaining the magnetic field characteristic of the sensor output is shown in FIG. It was possible to determine the direction and magnitude of the magnetic field in the range of -1 [Oe] to 2 [Oe]. This magnetic field range can be expanded by further applying a bias magnetic field. Further, a feedback coil is wound around the amorphous magnetic wire 1 in the same manner as the bias coil,
By having a double coil structure and feeding back the sensor output as a magnetic field with a feedback coil, the range in which the magnetic field can be detected is further expanded and the linearity is also improved.

Further, several tens of Colpitts oscillator type magnetic sensors according to the present invention were prototyped, and an experiment as to whether or not stable oscillation was performed was performed. As a result, stable oscillation was confirmed in all the sensors. From this result, it can be concluded that the Colpitts oscillator type magnetic sensor according to the present invention has completely solved the problem of stopping the oscillation, which was a problem in the conventional sensor.

[0023]

As described above, according to the Colpitts oscillator type magnetic sensor of the present invention, it is possible to solve the problem of the conventional sensor that the oscillation is stopped, and even if the input voltage fluctuates by several volts, or Even if the amorphous magnetic material is changed, stable oscillation can be ensured.

Further, according to the Colpitts oscillator type magnetic sensor of the present invention, since all the sensors can stably oscillate, the Colpitts oscillator type magnetic sensor can be mass-produced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of a Colpitts oscillator type magnetic sensor according to the present invention.

FIG. 2 is a graph showing an example of magnetic field characteristics of impedance of an amorphous magnetic wire.

FIG. 3 is a graph showing an output magnetic field characteristic of the Colpitts oscillator type magnetic sensor according to the present invention.

FIG. 4 is a circuit diagram showing a structure of a conventional Colpitts oscillator type magnetic sensor.

[Explanation of symbols]

 1 Amorphous Magnetic Wire 2 Resistor 3 Capacitor 4 Transistor 5 Resistor 6 Coil 7 Resistor 8 Capacitor 9 DC Converter Circuit 10 Amplifying Circuit 11 Terminal 12 Inductor

Claims (2)

[Claims] 1. A Colpitts oscillator type magnetic sensor in which an amorphous magnetic body is inserted in an inductance portion of a Colpitts oscillator, wherein an inductor Lα is arranged in series with the amorphous magnetic body. 2. When the amorphous magnetic body is regarded as an element in which a resistor Rw and an inductor Lw are connected in series, the inductor Lα is arranged so as to satisfy the following stable oscillation conditional expression (1). 2. The Colpitts oscillator type magnetic sensor according to claim 1. (ΩLw + ωLα) ² > Rw ² + ARw (1) In the equation (1), A = Rp · h _ie / Rp + h _ie h _ie : input resistance of the transistor Rp: combined resistance in parallel with h _ie ω: during oscillation Is the angular frequency of.