JPH03186781A - Magnetic detecting device - Google Patents

Abstract

PURPOSE:To automatically correct the sensitivity variance of a magnetic sensor in an extremely short time and with high accuracy by allowing an adjusting medium to pass through on the magnetic sensor detecting surface. CONSTITUTION:First of all, a prescribed value determined in advance, for instance, a digital value of the maximum output width being a target is a variable gain amplifier 5 is stored in a nonvolatile memory 9 in advance. Subsequently, a changeover switch is switched to a correction gain setting side, a correction gain setting signal is sent to a CPU 10 from an operation mode setting part 11, and the CPU 10 becomes a correction gain setting mode. Next, an adjusting medium having a wire rod 3 is carried at a constant speed V. The CPU 10 performs an operation to an output of a converter 6 obtained by carrying and the gain of an amplifier 5 at the time of obtaining the output, and derives the gain required for obtaining the output determined in advance. Thereafter, the derived value is stored in a memory 9 and the gain of the amplifier 5, and at the time of a regular operation mode, by setting this stored gain to a gain setting part 8, the sensitivity variance of a magnetic sensor 1 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic detection device, and particularly to a magnetic detection device suitable for use in a bill discriminating device that discriminates the type and authenticity of banknotes.

(Prior Art) For example, in a bill discriminating device that discriminates the type (denomination) and authenticity of a bill inserted into an automatic deposit/withdrawal machine or money exchange machine installed in a bank, etc., as one of the discriminating means, It is known that the denomination and authenticity can be determined by detecting the magnetic component of banknotes using a magnetic sensor and comparing the detection pattern and detection level with preset standard patterns and reference levels. .

However, magnetic sensors have sensitivity variations in their sensor elements, and these variations must be corrected in order to obtain a predetermined output.

In order to correct this variation, the present applicant has previously proposed an adjustment device for a banknote validating device (see Japanese Patent Application No. 88919/1988). An example of this is shown in FIG.

In the figure, a magnetic sensor 1, a resistor 14, a variable resistor 1
5 and operational amplifier 16 are components of a conventional magnetic detection device. 2 is an oscillator that outputs a sine wave of constant frequency and constant amplitude. 3 is a wire connected to the oscillator 2;
It is fixed to a sheet-shaped insulator 4 (hereinafter, the sheet-shaped insulator 4 to which the wire rod 3 is fixed is referred to as an adjustment medium). 1
Reference numeral 7 denotes an AC voltmeter that measures the output of an amplification circuit composed of a resistor 14, a variable resistor 15, and an operational amplifier 16.

First, a sinusoidal current i of a constant frequency and a constant amplitude is caused to flow through the cotton material 3 by the oscillator 2. This current i generates a magnetic field around the wire 3. If the strength of the magnetic field is expressed as H, it is known from Ampere's law that a magnetic field of 2ir is generated at a distance r from the wire 3.

Next, the adjustment medium is put into the bill discriminating device (bill discriminating device), the wire rod 3 fixed to the sheet-shaped insulator (insulating sheet) 4 is brought close to the detection surface of the magnetic sensor, and the AC voltmeter 17
The adjustment medium is fixed at a position where the indicated value E is maximum, that is, a position where the distance between the element of the magnetic sensor and the wire 3 is the minimum. At this time, it goes without saying that the output of the aforementioned amplifier circuit is a stationary sine wave.

Furthermore, the variable resistor 15 is adjusted so that the indicated value E of the AC voltmeter 17 becomes a predetermined value, and sensitivity variations in the magnetic sensor are corrected.

(Problem to be Solved by the Invention) However, in the device with the above configuration, when correcting sensitivity variations in the magnetic sensor, the distance between the wire through which current flows and the magnetic field is generated, and the magnetic sensor element is set at a certain distance. Since the variable resistor must be adjusted while the variable resistor is fixed and the value indicated by the voltmeter is checked, there is a problem that correction cannot be carried out in a short time.

Furthermore, due to the manual work, there is a problem in that the adjustment medium may be misaligned or the variable resistor may be misaligned, making it impossible to perform accurate correction.

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned problems, it is an object of the present invention to automatically correct variations in sensitivity of a magnetic sensor in an extremely short time and with high accuracy by simply passing an adjustment medium over the detection surface of the magnetic sensor. The object of the present invention is to provide a magnetic detection device capable of

(Means for Solving the Problems) In order to achieve the above object, a magnetic detection device of the present invention detects a magnetic component of a medium, in which the magnetic detection device is provided on an external medium conveying means, a detection means for detecting the component; a variable gain amplification means for amplifying the output of the detection means based on an arbitrarily set gain;
gain setting means for setting an arbitrary gain; conversion means for converting the output from the variable gain amplification means into a digital value; and either a correction mode or a normal operation mode for correcting sensitivity variations of the detection means. mode setting means for setting a mode; and only in the correction mode, an output of the conversion means, a gain of the variable gain amplification means when the output is obtained, and a predetermined target output value of the conversion means; and a non-volatile storage means for calculating a correction gain of the variable gain amplification means, wherein the magnetic field generating medium that generates a predetermined steady magnetic field is detected by the transport means in the correction mode. The calculation means calculates the output from the conversion means obtained by conveying the output over the detection section of the means and the gain of the variable gain amplification means when the output is obtained to obtain a predetermined output. The requested value is stored in the non-volatile storage means as the gain of the variable gain amplification means, and in the normal operation mode, the stored gain is set in the gain setting means and the detection means The feature is that it corrects the sensitivity variations of .

(Function) In the present invention, in the correction mode, the magnetic field generating medium that generates a predetermined steady magnetic field is conveyed by the conveying means over the detecting section of the detecting means. The calculation means performs calculations on the output and the gain of the variable gain amplification means when the output is obtained, calculates the gain necessary to obtain a predetermined output, and calculates the requested value as the variable gain. The gain of the amplification means is stored in the non-volatile storage means, and in the normal operation mode, the stored gain is set in the gain setting means to correct variations in sensitivity of the detection means.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram of a magnetic detection device showing one embodiment of the present invention.

In FIG. 1, l is a magnetic sensor, 2 is an oscillator, 3 is a cotton material, 4 is an insulating sheet, and 5 is a variable that amplifies the output e of the magnetic sensor 1 according to the gain G set by the gain setting section 8. The gain amplifier 6 is the output ex(:G
e+) into a digital value based on the sample signal from the PUIO, 7 is a register that temporarily stores the digital signal from the A/D converter 6, 8
C: a gain setting unit such as a latch circuit that supplies a signal for setting the gain to a specific value to the variable gain amplifier 5 based on the gain setting value signal from the PUIO; 9 is a predetermined value Dr to be described later; Correction gain Gr found by CPUl0
10 is a CPU (central processing unit) that controls a series of operations according to each operation mode set by the operation mode setting unit 11, and 11 is composed of an oscillator 2, a wire 3, and an insulating sheet 4. As will be described later, there is a correction gain setting mode, which is an operation mode in which the adjustment medium is passed over the detection surface of the magnetic sensor 1 by a conveying means (not shown) to determine the correction gain Gr, and a normal medium detection mode. This is an operation mode setting unit that sets the CPLIIO to either the normal operation mode or the normal operation mode in which it operates.

Here, the variable gain amplifier 5 and the gain setting section 8 are, for example,
The circuit configuration is as shown in FIG.
It is connected to l0, and the input signal is latched on the output side by a latch signal from cpuio. The input (D, ~D,) of the D/A converter 19 is connected to the output of the latch circuit 18, and a value proportional to the input (01~D,) and the reference input of the D/A converter 19 are connected to the output of the latch circuit 18. The product of D/A converter 1
It is output from the output section 9. Resistor 20.21. and an operational amplifier 22, which amplifies the output of the D/A converter 19 at a constant gain to the extent that it does not saturate in the subsequent A/D converter 6 and sufficient resolution can be obtained. Department.

Next, the operation of this embodiment will be explained with reference to FIGS. 1 and 2.

First, a predetermined value (in this embodiment, a digital value of the target maximum output width E2r in the variable gain amplifier 5) Dr is stored in the memory 9 in advance. Next, by switching a changeover switch (not shown) such as a toggle switch to the correction gain setting side, a correction gain setting signal is transmitted from the operation mode setting section 11 to the CPUTO, and the CPUTO enters the correction gain setting mode. . Then, the adjustment medium having the wire 3 generating a steady magnetic field by a sinusoidal current of a predetermined constant frequency and constant amplitude is conveyed at a constant speed V in the direction of the arrow by a conveying means (not shown).

Here, the relationship between the transport position of the wire 3 and the detection level of the magnetic sensor 1 is shown in FIG. In the figure, 2
The envelope curve of the book shows the amplitude of the detection level of the magnetic sensor 1 when the wire 3 is fixed at each position,
When the wire 3 is directly above the sensing element 13 of the magnetic sensor 1, its amplitude becomes the maximum amplitude Ep. The waveforms e° and e'' shown by the solid line and the dashed-dot line correspond to the conveyance speeds Vo and V''.
An example of the detection level of the magnetic sensor 1 when v'<v
In order to correct the sensitivity variations of the magnetic sensor in this embodiment without error, the maximum amplitude of the detection level of the magnetic sensor 1 must be equal to the maximum amplitude E described above.
p, but since the wire 3 is moving at a constant speed, the maximum amplitude is not necessarily detected. However, as shown in FIG. 3, by slowing down the conveyance speed, the maximum amplitude of the detection level of the magnetic sensor 1 can be brought closer to Ep. Therefore, the conveying speed V
is the maximum amplitude of the detection level of the magnetic sensor l (for example, the third
In the figure, the difference between Ep') and Ep is within the allowable error range, that is, the speed is such that the required correction accuracy is satisfied, or the transport speed is determined. If so, the frequency of the magnetic field generated by the adjustment medium may be relatively increased.

When the arrival of the adjustment medium is detected by a medium detection means (not shown) in which a detection section is arranged in line with the magnetic sensor 1 in the transport direction, a medium detection signal is transmitted to the CPUIG. C
Upon receiving this medium detection signal, PUl0 first sets the gain G0 of the variable gain amplifier 5 to a level that does not saturate the output of the A/D converter 6 and provides sufficient resolution. Then, the gain setting value signal is supplied to the gain setting section 8.

After that, the CPU10 reads the output of the A/D converter 6, and the positive peak value D of the output from the time of starting reading.
The amplitude Dp (D
p, -Dp-) and stores Dp in a register (not shown) built into CPU10.

When the rear end of the adjustment medium passes through the detection section of the medium detection means, a medium passage signal is transmitted to CPU10. C.P.
When Ul0 receives this medium passing signal, it first converts the A/D
Stop reading the output of the converter 6. Then CPUl
0 reads out the predetermined value Dr mentioned above from the memory 9 and calculates the correction gain Gr as follows. However, it is assumed that the variable gain amplifier 5 and the A/D converter 6 perform linear amplification (e2·Ge+) and linear conversion (D-de*) with respect to the gain G, respectively.

Go: Dp= Gr: Dr r,', Gr" Go- Dp Then, the CPU 10 sends the gain setting value signal to the gain setting unit 8 so that the gain of the variable gain amplifier 5 becomes the correction gain Gr obtained by the above calculation. and stores it in the non-volatile memory 9.Finally, by switching the aforementioned changeover switch (not shown) to the normal operation side, the normal operation signal is sent from the operation mode setting section 11 to the cputo. The correction gain setting operation is completed and normal operation resumes.

Note that when the magnetic sensor l can detect a static magnetic field, the wire rod 3
It is not necessary that the current flowing through the sensor is a sine wave, and it is possible to perform correction by flowing a direct current.

In the above embodiment, a non-volatile memory is used, but a configuration in which a volatile memory is used for a power supply buffer, etc. can be similarly applied.

(Effects of the Invention) As explained above, according to the present invention, sensitivity variations in the magnetic sensor can be automatically corrected by simply setting the mode and transporting the adjustment medium over the magnetic sensor detection surface. Therefore, corrections can be made in an extremely short time, and
Human adjustment errors are eliminated, and correction can be performed with extremely high precision.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a magnetic detection device showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the gain setting method of the variable gain amplifier in Fig. 1, and Fig. 3 shows the wire transport position and A diagram showing the relationship with the detection level of the magnetic sensor, FIG. 4 is a diagram for explaining a conventional example. 1: Magnetic sensor, 2: Oscillator, wire, variable gain amplifier, register, memory, operation mode setting section, detection element, D/A converter, operational amplifier. Insulating sheet, A/D converter, gain setting section, CPU. bus, latch circuit, 21: resistor,

Claims (1)

[Scope of Claims] A magnetic detection device that detects a magnetic component of a medium, comprising: a detection device that is provided on an external medium conveyance device and detects a magnetic component of the medium; and a gain that is arbitrarily set. variable gain amplification means for amplifying the output from the detection means; gain setting means for setting an arbitrary gain; conversion means for converting the output from the variable gain amplification means into a digital value; and sensitivity of the detection means. mode setting means for setting the mode to either a correction mode for correcting variations or a normal operation mode; and only in the correction mode, the output of the conversion means and the variable gain amplification means when the output is obtained; arithmetic means for calculating a correction gain of the variable gain amplification means from a gain and a predetermined target output value of the conversion means; and non-volatile storage means, the method comprising: a calculation means for calculating a correction gain of the variable gain amplification means from a gain and a predetermined target output value of the conversion means; and a nonvolatile storage means; The output from the converting means obtained by transporting the generated magnetic field generating medium over the detecting section of the detecting means by the transport means and the gain of the variable gain amplifying means when the output is obtained. performing a calculation by a calculation means to determine the gain necessary to obtain a predetermined output, and storing the determined value in the nonvolatile storage means as the gain of the variable gain amplification means;
A magnetic detection device characterized in that, in a normal operation mode, the stored gain is set in the gain setting means to correct variations in sensitivity of the detection means.