JP2001264455A - Sensitiveness adjusting device in metal detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem such that adjustment to an optimum sensitiveness is prone to be affected by a temperature change or electric noise and very difficult in a conventional sensitiveness adjusting method varying amplitude magnitude of an amplifying circuit or a determination point in a determination circuit generally in a sensitiveness adjusting device in an oscillation type metal detector. SOLUTION: A metal object is brought close to an oscillation part in an oscillation circuit, and the metal object is fixed just before an oscillation limit point. Under this condition, the oscillation circuit shows a great change by an approach of other metals. Therefore, this sensitive adjusting device physically adjusts sensitiveness by varying a distance between the oscillation circuit and the sensitiveness regulating metal and can adjust the optimum sensitiveness in a metal detector without any influence of electric noise and a temperature change caused by electrical regulation such as an increase in magnitude of the amplifying circuit and an increase in a variable in determination point adjustment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensitivity adjusting device for an oscillation type metal detector.

[0002]

2. Description of the Related Art FIG. 1 shows a basic configuration of a general metal detector. An oscillating circuit 1 serving as a metal sensor, an amplifying circuit 2 for amplifying a waveform oscillated by the oscillating circuit 1, a determining circuit 3 for comparing a signal amplified by the amplifying circuit 2 with a determining point, and a determining circuit 3 When a signal is output, a metal detector having an alarm circuit 4 for notifying the detection of metal,
A series of operations up to metal detection will be described below.

When a metal body approaches the oscillation circuit 1 which is a metal sensor, a small change occurs in the amplitude of a waveform generated by the oscillation circuit 1. This minute change is amplified by the amplifier circuit 2 and a signal is output to the determination circuit. The decision circuit 3 outputs a signal to the alarm circuit 4 when the signal output from the amplifier circuit 2 exceeds the decision point. When this signal is input, the alarm circuit 4 issues an alarm lamp or an alarm sound, or operates a vibrator motor or the like to notify the detection of metal.

[0004] In the above-described metal detector, a sensitivity adjusting device has been conventionally added, and the adjusting method is to change an amplification factor of an amplifier circuit as described below,
This is to change the judgment point of the judgment circuit.

A method for adjusting the detection sensitivity by changing the amplification factor of the amplifier circuit will be described. By increasing the amplification factor using a variable resistor or the like, the amount of change in the amplitude of the waveform when the minute metal approaches the oscillation circuit can be calculated from the difference between the amplitudes of the waveform before the use of the controller and AB in FIG. Also in FIG.
-D is larger. The determination circuit 3 does not output a signal to the notification circuit and does not report the detection of the metal because AB does not exceed the determination point in AB of FIG. In the case of CD in FIG. 3 in which the difference between the changes in the amplitude has increased, a signal is output because the difference exceeds the judgment point G, and the alarm circuit operates to issue a metal detection.

A description will be given of a method for adjusting the detection sensitivity by changing the judgment point of the judgment circuit. By changing the judgment point using a variable resistor or the like, the judgment circuit 3 has a small change in the amplitude of the waveform when the minute metal approaches the oscillation circuit, and the change in the amplitude of the waveform input to the judgment circuit is small. When the difference AB is small, the signal does not exceed the judgment point G as shown in FIG. 2, so that no signal is output to the alarm circuit and no metal detection is issued, but the judgment point is changed from G to H. By
As shown in FIG. 4, a signal is output because the difference AB in the amplitude change in the waveform input to the judgment circuit exceeds the judgment point H, and the alarm circuit operates to issue a metal detection.

[0007]

When the sensitivity is adjusted to the maximum sensitivity using the conventional sensitivity adjusting device, the sensitivity adjusting device for adjusting the amplification factor of the amplifier detects that the amplification factor is increased as shown in FIG. Although the sensitivity is improved, the amount of change when the amplitude of the oscillating waveform changes due to temperature changes in the oscillation circuit and the electrical noise included in the oscillating waveform are also amplified, so the decision circuit is required. The input signal may exceed the judgment point as shown in FIG.
For this reason, it is necessary to take a large difference between the signal input to the decision circuit and the decision point, and it is difficult to adjust the sensitivity to the maximum.

In a sensitivity adjusting device for adjusting the judgment point of the judgment circuit, when the signal inputted to the judgment circuit is brought close to the judgment point as shown in FIG. 4, the detection sensitivity is improved.
The judgment point changes from H to K due to temperature change and electrical noise
, The decision point may exceed the signal input to the decision circuit. For this reason, as described above, the difference between the signal input to the decision circuit and the decision point must be made large, and it is difficult to adjust the sensitivity to the maximum.

[0009]

Means for Solving the Problems In order to solve the aforementioned problems,
In the sensitivity adjusting device of the present invention, a metal object for sensitivity adjustment is brought close to the oscillating portion of the oscillation circuit 1 and the distance is adjusted, so that when other metal objects approach the oscillating portion, the oscillation amplitude is reduced. The amount of change is set to be larger than when there is no metal object for sensitivity adjustment.

[0010]

Embodiments of the present invention will be described below. As described above, when a metal object is brought close to the oscillation circuit which is a metal sensor, the waveform oscillated by the oscillation circuit changes. Here, when the distance between the oscillation circuit and the metal object is further reduced, there is a point where oscillation in the oscillation circuit stops. The point immediately before the oscillation stops is defined as an oscillation limit point.

The change in the oscillation amplitude when a metal object approaches the oscillation circuit oscillating at the oscillation limit point is the change in the oscillation amplitude when the metal object approaches the normally oscillating circuit. Several times larger than For this reason, it is not necessary to increase the amplification factor of the amplifier circuit, and it is possible to prevent the amount of change in oscillation amplitude and electric noise due to temperature change from being wasted unnecessarily while improving the detection sensitivity. Also, since the change amount of the oscillation amplitude becomes large, it is not necessary to bring the signal inputted to the judgment circuit close to the judgment point, and it is possible to eliminate a false alarm of metal detection due to a change in the judgment point due to a temperature change or the like. is there.

However, the oscillation amplitude of the waveform oscillating in the oscillation circuit slightly changes depending on the temperature as described above.
Similarly, the oscillation amplitude of the waveform oscillating at the oscillation limit point also changes. That is, since the oscillation limit point fluctuates due to a change in temperature, the sensitivity adjustment device of the present invention can be used with an oscillation circuit, which is a metal sensor, according to the change in the oscillation limit point as shown in the embodiment of FIGS. By changing the distance between metal objects, the sensitivity can be easily adjusted to the highest sensitivity.

[0013]

As described above, the sensitivity adjusting device according to the first aspect of the present invention has a sensitivity higher than that of the conventional sensitivity adjusting device by bringing the metal object for adjusting the sensitivity close to the oscillation circuit. It is possible to improve.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of a metal detector.

FIG. 2 shows an oscillation waveform A output from an amplification circuit 2, an oscillation waveform B when a metal object approaches the oscillation circuit 1, and a decision point G.

FIG. 3 shows an oscillation waveform C output from an amplification circuit 2 with an increased amplification factor, an oscillation waveform D when a metal object approaches the oscillation circuit 1, and a decision point G.

FIG. 4 is an oscillation waveform A output from an amplifier circuit 2 in a judgment circuit 3, an oscillation waveform B when a metal object approaches the oscillation circuit 1, and a changed judgment point H.

FIG. 5 is an output from an amplifier circuit 2 having an increased amplification factor.
Oscillation waveform E including electrical noise and decision point G

FIG. 6 shows an oscillation waveform A output from an amplifier circuit 2 in a decision circuit 3, a decision point H, and a decision point K that fluctuates due to a temperature change.

FIG. 7 is a metal detector 1 using the sensitivity adjusting device of the present invention.

FIG. 8 is a sensitivity adjustment method of the sensitivity adjustment device of the present invention.

FIG. 9 shows a metal detector 2 using the sensitivity adjusting device of the present invention.

FIG. 10 shows a metal detector 3 using the sensitivity adjusting device of the present invention.

[Explanation of symbols]

1. Oscillation circuit 2. 2. Amplifier circuit Judgment circuit Alarm circuit 5. 5. Metal object for sensitivity adjustment Control board 7. Battery 8. Main body case 9. Power switch 10. Sensitivity adjustment knob A. Oscillation waveform output from amplifier circuit 2 B. B. Oscillation waveform when a metal object approaches oscillation circuit 1 C. Oscillation waveform output from amplification circuit 2 with increased amplification factor G. Oscillation waveform when a metal object approaches oscillator circuit 1 Decision point H. Changed decision point K. Judgment point changed by temperature change

Claims (1)

[Claims] 1. A sensitivity adjusting device, wherein a metal object is brought close to a metal sensor to mechanically adjust the metal detection sensitivity.