JPS63157082A - Method for adjusting sensitivity of magnetic sensor of paper currency discriminating device - Google Patents

Abstract

PURPOSE:To improve paper currency discrimination accuracy by producing a magnetic field at the periphery of a magnetic sensor, finding the sensitivity of the magnetic sensor from the output of the magnetic sensor and the intensity of the magnetism, and adjusting this sensitivity with an adjustment coefficient. CONSTITUTION:A magnetic head 1 consists of a core 1a which is provided with a coil 1c and constitutes a closed magnetic path and a magnetic gap 1b. When a current is supplied to a linear electric conductor 2 from a power source 3 by the switching of a switch 8 at the time of paper currency discrimination, a magnetic layer, etc., on the surface of paper currency are magnetized with a DC bias current right before the head 1 to produce residual magnetic flux. The density of this residual magnetic flux varies with time as the paper currency is conveyed and is inputted to the head 1 and outputs as voltage variation from both ends of the coil 1c. The output signal (voltage) of this head 1 is supplied to a microcomputer 9 through an amplifier 6, an A/D converter 7, and the switch 8. Then the computer 9 multiplies the output signal by the adjustment coefficient which is already stored in a memory according to the output value of the head 1 to make an adjustment. Thus the paper currency discrimination accuracy can be improved.

Description

[Detailed description of the invention] [Industrial application field]

This invention relates to a method for adjusting magnetic sensor sensitivity of a banknote validating device;
In particular, the present invention relates to a method of determining the sensitivity of a magnetic sensor by measuring the output of the magnetic sensor due to a magnetic field applied to the surroundings, and adjusting this sensitivity to an apparent predetermined level.

[Conventional technology] Conventionally, to adjust the sensitivity of this type of magnetic sensor, a piece of magnetic printing paper (with a magnetic layer formed on the surface) is conveyed in front of the magnetic sensor, the dynamic magnetic sensor output is measured, and this output is Based on the value, the sensitivity of the magnetic sensor has been adjusted to an apparently predetermined level. In general, since there is "variation" in the sensitivity of magnetic sensors, it is necessary to adjust the "variation" in sensitivity of each magnetic sensor to a predetermined level (reference value). By doing so, when the magnetic characteristics of the banknote to be discriminated are detected, the difference in the detected value due to the difference in sensitivity of the magnetic sensor is corrected, and subsequent data processing can be performed appropriately. Note that the magnetic properties of a banknote are often detected by a magnetic sensor □ magnetic head or a magnetoresistive element □ as an integral value for a certain passage time at each predetermined location on the surface. Then, the authenticity or type of the banknote is determined based on the pattern of the integrated values. [Problems to be solved by the invention]

In the conventional method as explained above, the magnetic properties of the magnetic printing paper itself change over time and are affected by environmental changes such as temperature and humidity; therefore, sensitivity measurement or output based on this There is a problem that an error occurs in the adjustment; or that it is troublesome to correct the error. The purpose of this invention is to solve the problems of the conventional technology, to measure the output of a magnetic sensor based on a magnetic state that is not affected by aging or environmental changes, and to Find the sensitivity of the sensor, and the apparent sensitivity is above,
An object of the present invention is to provide a method for adjusting the sensitivity of a magnetic sensor of a banknote validating device, which adjusts the sensitivity to a predetermined level (reference value).

[Means to solve the problem]

In order to achieve the above object, the present invention has the following configuration. (1) Create a magnetic field around a magnetic sensor installed in a bill validator, (2) Obtain the resulting output of the magnetic sensor, and (3) Calculate the magnetic sensor based on this output and the strength of the magnetic field. Find the sensitivity of (4) Adjust this sensitivity to a predetermined level (reference value), which is apparently above. Note that the magnetic field can be created by a linear current flowing parallel to the front surface of the magnetic sensor, or by a solenoid current that passes through the center of the front surface of the magnetic sensor and has an axis perpendicular to this front surface. When the magnetic sensor is a magnetic head, the magnetic field can be an alternating magnetic field whose intensity changes periodically over time. Further, when the magnetic sensor is a magnetoresistive element, the magnetic field can be a steady magnetic field whose strength is constant.

[For use]

Since the configuration is as explained above, the operation of the present invention is as follows. If the strength of the magnetic field created around the magnetic sensor is Hl, the output of the magnetic sensor generated by this is ■, and the magnetic sensor output when the magnetic field strength is zero (no magnetic field) is Vo, then the sensitivity of this magnetic sensor is S can be determined by S=(V-Vo)/H. However, it is assumed that the magnetic sensor output has a linear characteristic with respect to the strength of the magnetic field. In order to apparently adjust the magnetic sensor sensitivity S to a predetermined level (reference value) So, an adjustment coefficient K defined as follows can be determined. K=So/S This adjustment coefficient includes differences in the sensitivity of individual magnetic sensors, that is, "variations" that appear to be above a predetermined level (standard value) So
Represents the degree of adjustment required to adjust the In other words, the fact that the adjustment coefficient K is large means that because the inherent sensitivity S of the magnetic sensor is small, it is necessary to make a large adjustment in order to obtain the sensitivity at the predetermined level (reference value) So, although it looks good. do.

【Example】

An embodiment of the present invention will be described below with reference to the block diagram of the embodiment shown in FIG. In Figure 1, 1 is a magnetic head as a magnetic sensor, 2 is a straight wire for creating a magnetic field, 3 is a commercial power supply, 6 is an amplifier, 7 is an A/D converter, 8 is a switch, and 9 is a microcomputer. It is. The magnetic helad 1 basically consists of a core 1a having a coil 1c and forming a closed magnetic path made of a magnetic material, and a magnetic gap 1b provided in a portion of the core 1a facing the recording medium. The switch 8 supplies or stops the power supply from the power source 3 to the straight wire 2, and also amplifies the output signal (voltage) of the magnetic herad 1 through the amplifier 6 and the A/D converter 7. The converted data is input to the microcomputer 9 for a predetermined period of time. Since the configuration is as explained above, the operation of this embodiment is as follows. By supplying power from the power source 3, an alternating linear current flowing through the straight wire 2 forms a concentric alternating magnetic field around it. Since the magnetic head 1 operates based on a velocity differential type operation principle, a temporally varying magnetic flux due to an alternating magnetic field enters from the magnetic gap 1b, goes around the core 1a, and interlinks with the coil lc. As a result, a voltage induced across the coil lc according to the law of electromagnetic induction is extracted from both ends as an output signal (voltage). The magnitude of this output signal is approximately proportional to the temporal rate of change of the magnetic field created around the straight wire 2. ,. Temporal rate of change in the strength H of the magnetic field around the magnetic head l:
D=dH/d t, the magnetic head 1 comes out due to this, and the magnetic head 1 comes out when the current flowing through the straight wire 2 is zero, that is, the magnetic field strength H is zero (no magnetic field). Then, the sensitivity S of this magnetic head l can be found as S - (V - Vo)/D. However, it is assumed that the output (2) of the magnetic head 1 with respect to the temporal change rate of the magnetic field strength H has a linear characteristic. The sensitivity S of this magnetic head 1 is apparently higher than the reference value So.
In order to make the adjustment, the following adjustment coefficient K is determined. K=So/S This adjustment coefficient includes each adjustment factor that is used to adjust the difference in sensitivity of each of the plurality of magnetic heads incorporated in one banknote validator, that is, the "variation", to the standard value So, which is apparently good. Represents the degree of adjustment of sensitivity. A large adjustment coefficient K means that the inherent sensitivity S of the magnetic head is small, so the appearance is higher, and the sensitivity is increased to the standard value S. This means that adjustment is necessary □.The calculation for determining the adjustment coefficient K as explained above is performed by the microcomputer 9, and the resulting value of the adjustment coefficient corresponding to each magnetic head is calculated by the microcomputer 9. 9
stored in memory. When validating banknotes, the magnetic layer □ on the surface of the banknote, which has a magnetic strength and distribution pattern unique to the banknote, is magnetized by a direct current bias current immediately before the magnetic head, and a residual magnetic flux is formed. The density of this residual magnetic flux changes over time as the banknote is conveyed, and is captured by the magnetic head 1.
It is output as a voltage change from both ends of the coil 1c. This output value is corrected (adjusted) by the microcomputer 9 by multiplying it by an adjustment coefficient K already stored in the memory corresponding to the magnetic head l.Based on this correction (adjustment) value, Subsequent data processing is performed to determine whether one type of banknote is genuine or false. Another embodiment will be described with reference to FIG. This embodiment differs from the first described embodiment in that the magnetic sensor is a magnetoresistive element 11 and the magnetic field is generated by a solenoid 12. The magnetoresistive element 11 is a type of magnetoelectric conversion element, and is a solid electronic component configured to extract the strength of a magnetic field as a change in electrical resistance. As shown in FIG. 2, a magnetoresistive element 11, a battery 14, and a variable resistor 15 are connected in series, and a solenoid 12 is installed opposite the magnetoresistive element 11. Electric power is supplied from a battery 13 to this solenoid 12, and a steady current flows therethrough. This steady current forms a steady magnetic field whose main direction is the axial direction of the solenoid 12. The output signal (voltage) taken out from both ends of the magnetoresistive element 11 is approximately proportional to the strength of the magnetic field generated by the solenoid 12. This output signal is transmitted to the amplifier 6, the A/D converter 7,
The signal is sent to the microcomputer 9 via the switch 8. The amplifier 6, A/D converter 7, switch 8, and microcomputer 9 are functionally the same as those shown in FIG. 1. Strength of the magnetic field around the magnetoresistive element 11: H1 The output of the magnetic head l caused by this V1 The output of the magnetoresistive element 11 when the current flowing through the solenoid 12 is zero, that is, the strength of the magnetic field is zero (no magnetic field), then the output of the magnetoresistive element 11 is Sensitivity S can be determined by S = (V-Vo)/H. However, it is assumed that the output of magnetoresistive element 11 with respect to the strength of the magnetic field has linear characteristics. Sensitivity S of this magnetoresistive element 11 In order to apparently adjust the reference value So, the following adjustment coefficient K is determined: K=So/S This adjustment coefficient K has already been explained in the first embodiment. Similarly, the calculation for determining the adjustment coefficient K is performed by the microcomputer 9, and the resulting value of the adjustment coefficient corresponding to each magnetoresistive element is stored in the memory. Symbols used, magnetic field strength H1 output V
For convenience, the same symbols as in the first embodiment are used for n Vo s G degree S, So, adjustment coefficient, etc. Now, when validating a banknote, the magnetic layer on the surface of the banknote is magnetized by a permanent magnet built into the banknote validating device immediately before the magnetoresistive element 11, and a residual magnetic flux is formed. The density of this residual magnetic flux is converted by the magnetoresistive element 11 and output as a voltage signal from terminals at both ends thereof. This output value is corrected (adjusted) by the microcomputer 9 by multiplying it by an adjustment coefficient K already stored in its memory, corresponding to the magnetoresistive element 11. Based on this correction (adjustment) value, subsequent data processing is performed to determine whether one type of banknote is genuine or false.

【Effect of the invention】

As explained above, in the present invention, a magnetic field is created around a magnetic sensor provided in a bill validator, the resulting output of the magnetic sensor is determined, and the output of the magnetic sensor is determined based on this output and the strength of the magnetic field. The sensitivity of the magnetic sensor was determined, and the sensitivity was adjusted to a predetermined level, which was apparently better. Therefore, the present invention has the following superior effects compared to the conventional technology. (11) The generated magnetic field is accurate in its strength and direction, and has excellent reproducibility.Since the magnetic sensor output is measured based on this magnetic field, the accuracy of the measured value is high, and therefore accurate sensitivity adjustment is possible. (2) Since the output of the magnetic sensor can be measured while it is attached to the actual device, conversion errors and errors due to differences in condition can be removed, and the measured value Of course, is accurate;
Measurement work is easy and can be done in a short time. (3) The method of creating the magnetic field can be conveniently selected depending on the situation at the time. (4) Means for Adjusting Sensitivity of Magnetic Sensor It is also possible to discover defects in the magnetic sensor by using the procedure 1 as is.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a block diagram of another embodiment. Code explanation 1: Magnetic to 7 de, lai core, lb: T61 kigi +7
1c: Coil, 2: Straight wire, 3: Power supply, 6: Amplifier, '7: A/D converter, 8: Switch, 9: Microcomputer, 11: [Air resistance element, 12: Solenoid, 13 .14: Battery, 15: Variable resistance.

Claims (1)

[Claims] 1) A magnetic field is created around a magnetic sensor provided in a bill validating device, the resulting output of the magnetic sensor is determined, and the output of the magnetic sensor is determined based on this output and the strength of the magnetic field. 1. A method for adjusting sensitivity of a magnetic sensor for a banknote validating device, characterized in that sensitivity is determined and the sensitivity is apparently adjusted to a predetermined level. 2) A method for adjusting the sensitivity of a magnetic sensor for a banknote validating device according to claim 1, wherein the magnetic field is caused by a linear current flowing parallel to the front surface of the magnetic sensor. 3) A method for adjusting the sensitivity of a magnetic sensor for a banknote validator, wherein the magnetic field is generated by a solenoid current that passes through the center of the front of the magnetic sensor and has an axis perpendicular to the front of the magnetic sensor. . 4) In the method according to any one of claims 1 to 3, the magnetic sensor is a magnetic head, and the magnetic field is an alternating magnetic field whose rate of change with respect to time is periodically changed. A method for adjusting sensitivity of a magnetic sensor of a banknote validating device, characterized by using a magnetic field. 5) In the method according to any one of claims 1 to 3, the magnetic sensor is a magnetoresistive element, and the magnetic field is a steady magnetic field whose strength is constant. A magnetic sensor sensitivity adjustment method for a banknote validating device.