JPS63120273A - Security sensor - Google Patents

Abstract

PURPOSE:To increase the precision in detection of a magnetic field and the reliability, to obtain excellent sensitivity to detect a magnet and the like, and thereby to protect a magnetic recording carrier in an electronic computer room and the like, by coupling a transmission coil and a reception coil magnetically to form a detecting element. CONSTITUTION:A reception coil 6 is fitted with a magnetic core 7 formed ribbon-like of an amorphous magnetic material and is provided in a state of magnetic coupling with a transmission coil 5, so as to form a detecting element 56. When a bias magnetic field generated by a magnet M acts on the element, harmonic components of even-numbered order for a received frequency (f) appear in the coil 6, and these components are extracted through BPF10, 11 of 2f, 3f respectively and compared with each other by a comparator 12. An output obtained through comparison is displayed 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention protects magnetic record carriers, such as magnetic tapes or magnetic disks, for example in computer rooms or computer rooms, from destruction due to the proximity of other magnetic possessions. Eavesdrop on the security sensor.

[Conventional technology]

Conventionally, in computer rooms, large amounts of information have been stored on magnetic recording carriers such as magnetic tapes or magnetic disks, and a wide variety of processes have been carried out, and the magnetic force required for recording and extraction has also increased. Their performance is gradually improving so that they can be made smaller. On the other hand, electric appliances or electronic appliances are becoming increasingly smaller and more portable due to improved performance of their component parts. Especially regarding magnets as equipment components,
Even though it is small, it has an extremely large magnetic force built into it.

[Problem that the invention seeks to solve]

Under the above circumstances, there is a risk that magnetic objects may be brought into the electronic room or computer room inadvertently, and if they come close to the magnetic recording carrier, the stored information may be lost or A situation of destruction occurs. In order to avoid this situation, attempts have been made to create prototype magnetic field detection means, but the detection sensitivity is low, the detection accuracy and reliability are unsatisfactory, and most are defenseless against the proximity of magnetic objects. There is a problem that.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems existing in the prior art described above, and to provide a security sensor that has significantly higher detection accuracy and reliability, and has good sensitivity.

[Means for solving problems]

In order to solve the above problems, in the present invention, A. The transmitting coil is connected to transmitting means configured to be able to apply an alternating current voltage having a frequency r.

B. The receiving coil is connected to receiving means whose components include means for extracting alternating current voltages corresponding to frequencies 21 and 3'' and means for comparing both received current voltages.

A magnetic core made of an amorphous magnetic material is attached to the C1 receiving coil.

D. The transmitter coil and the receiver coil are arranged in a magnetically coupled state to form a detection section.

E. The detected magnetic field acting on this detection section is detected as the output of the comparison means.

This technical method was adopted.

[Effect]

With the above configuration, when no magnetic field acts on the detection part, the output voltage is O, but when a magnetic field acts on the detection part,
AC voltages having frequencies of 2f and 3f are generated in the receiving coil, and a component of frequency 2f appears largely. Therefore, since it can be detected as an output from the comparison means, this output can be displayed as an alarm or other signal, or can be used as a trigger for a device for preventing entry of persons carrying magnetic possessions, thereby protecting the magnetic record carrier. It has an effect.

〔Example〕

FIG. 1 is an explanatory diagram of the equipment configuration showing an embodiment of the present invention.

In the figure, l is an oscillator, one end of which is grounded, and oscillates an alternating current voltage with a frequency f. Reference numerals 2 and 3 denote 2r and 3[notch filters, respectively, which are connected in series with the oscillator 1 and formed to remove harmonics of twice and three times the frequency r, respectively. Reference numeral 4 denotes an amplifier, which has a function of amplifying the alternating current voltage after the harmonics have been removed. 5
6 is a transmitter coil connected in series with the amplifier 4 and has one end grounded, and 6 is a receiver coil, which is equipped with a magnetic core 7 formed into a ribbon shape of an amorphous magnetic material. A detecting section 56 is formed by being arranged in a magnetically coupled state with the transmitting coil 5 . 8.9 is an If notch filter and an amplifier, respectively, which have functions of removing the alternating current voltage of the fundamental frequency of the frequency f and amplifying harmonics of an integral multiple of the frequency f, and are connected in series with the receiving coil 6. Connecting. Reference numerals 10 and 11 are a 2f bandpass filter and a 3f bandpass filter, respectively, which are arranged in parallel to extract harmonic voltages of frequencies 21 and 3'', respectively, from harmonic voltages that are integral multiples of the frequency f. It is configured so that it can be extracted and output to the comparator 12. Reference numeral 13 is a display device, which is connected in series with the comparator 12 and is a means for visualizing its output.

With the above configuration, if the detection unit 56 is installed, for example, at the entrance of a computer room or a computer room (not shown), an output is generated in the comparator 12 due to the action of the magnetic field of the magnet M, and is displayed on the display device. Therefore, it is possible to prevent people carrying Magnet M from entering the room. Further, the output of the comparator 12 can also be inputted as a trigger for, for example, a locking device for an entrance door or an alarm device. Note that when no magnetic field acts on the detection section 56, no output is generated from the comparator 12.

That is, the receiving coil 6 has a magnetic core 7 made of an amorphous M magnetic material.
, the B-H curve is shifted by the action of a bias magnetic field such as the magnet M, and even harmonics such as 2f and 4r- appear with respect to the receiving frequency f.

FIG. 2 is a diagram showing the above state, and is a diagram showing the relationship between the bias magnetic field acting on the receiving coil 6 in FIG. 1 and the output voltage using the drive magnetic field as a parameter. As is clear from the figure, even if the magnetic field exerted on the transmitting coil 5 and the receiving coil 6 by the magnet 7) M, which is the object to be detected in FIG. In Fig. 2, a driving magnetic field of 0.400 peak is applied (thereby, an output voltage of 2 to 3 cm is obtained. In other words, by the bias magnetic field from the magnet M acting on the receiving coil 6, the receiving frequency is f
Since even-order harmonics appear, these are extracted through the 2f and 3r bandpass filters 10 and 11, and compared by the comparator 12 to obtain an output. Note that the magnetic field of 0.080e in the above example is a magnetic field at a distance of about 50 cjl from the surface magnetic field 1000e of the magnet, and such a weak magnetic field cannot be detected by ordinary detection means. By displaying the output obtained as described above as an alarm or other (i), it is possible to prevent magnets or magnetic objects from being inadvertently brought into the storage room for magnetic recording media.

In this embodiment, an example is shown in which the transmitting coil and the receiving coil are arranged at a distance, but even if they are integrated, the effect is the same, and the two are in a magnetically coupled state. Any configuration is sufficient as long as the magnetic field to be detected can act as a bias magnetic field on the detection section formed by the transmitting coil and the receiving coil.

〔Effect of the invention〕

Since the present invention has the structure and operation as described above,
It has extremely high detection sensitivity and reliability, and is extremely sensitive, so it can detect even weak magnetic fields, and can prevent magnetic items from being inadvertently brought into the magnetic recording media storage room. There is an effect.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the equipment configuration showing an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the bias magnetic field acting on the receiving coil in FIG. 1 and the output voltage using the drive magnetic field as a parameter. 5: Transmitting coil, 6: Receiving coil, 7: Magnetic core, M: Magnet.

Claims (3)

[Claims] (1) A transmitting coil connected to a transmitting means configured to be able to apply an alternating current voltage of frequency f, a receiving means having as its components an extracting means for alternating current voltages corresponding to frequencies 2f and 3f, and means for comparing both alternating voltages; A receiving coil having a magnetic core made of an amorphous magnetic material connected thereto is arranged in a magnetically coupled state to form a detecting section, and the detected magnetic field acting on the detecting section is detected by the comparing means. A security sensor that detects the output of (2) The security sensor according to claim 1, wherein the magnetic core attached to the receiving coil is formed into a ribbon shape. (3) A security sensor according to claim 1 or 2, in which the transmitting coil and the receiving coil are integrally formed.