CN103427764A - Oscillator for metal detector - Google Patents
Oscillator for metal detector Download PDFInfo
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- CN103427764A CN103427764A CN2013103815048A CN201310381504A CN103427764A CN 103427764 A CN103427764 A CN 103427764A CN 2013103815048 A CN2013103815048 A CN 2013103815048A CN 201310381504 A CN201310381504 A CN 201310381504A CN 103427764 A CN103427764 A CN 103427764A
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- 239000002184 metal Substances 0.000 title claims abstract description 15
- 230000010355 oscillation Effects 0.000 abstract description 10
- 230000035945 sensitivity Effects 0.000 abstract description 6
- 230000001939 inductive effect Effects 0.000 abstract 2
- 230000000630 rising effect Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000010276 construction Methods 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 238000004804 winding Methods 0.000 description 1
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Abstract
The invention discloses an oscillator for a metal detector. The oscillator structurally comprises a comparator circuit, a setting circuit and a switching circuit, wherein the comparator circuit is used for comparing voltage signals, the setting circuit is used for generating a reference signal voltage, and the switching circuit switches an inductance signal to the voltage. The oscillator is characterized in that the setting circuit forms a reference voltage uj at the inverting input end of a voltage comparator, the switching circuit is composed of a coil Lq and a resistor R and forms an inductive signal voltage ur at the non-inverting input end of the voltage comparator, the inductive signal voltage ur changes according to the index curve, the oscillator outputs a square wave signal uo, and the frequency of the oscillator is determined by the specific value r/1h of the resistance value r of the resistor R and the inductance value 1h of the coil Lq. Compared with an existing inductance and capacitance parallel resonance oscillator, the oscillator has the advantages that under the situation that the oscillation frequency, the inductance value and the inductance variation value are equal respectively, the frequency deviation of the oscillator is once larger than that of the existing oscillator, the oscillator has the higher sensitivity, the waveform of an output signal of the oscillator is square, the signal amplitude is stable, and the anti-jamming capability is strong.
Description
Technical field
The present invention relates to a kind of oscillator, this oscillator is for metal detecting device.
Background technology
In metal detector, usually adopt inductance, Capacitance parallel connection resonant oscillator as the transducer of surveying metal, it is several that the circuit types of described inductance, Capacitance parallel connection resonant oscillator mainly contains transformer feedback sine-wave oscillator, capacitive feedback sine-wave oscillator etc., described inductance is a coil, when the close metallic object of coil, the inductance value of coil can change, thereby resonance frequency is offset, according to the variation of frequency is detectable, goes out metallic object.The sensitivity that the frequency of oscillation of this oscillator changes inductance value is lower, and the frequency offset produced when inductance value changes is less, simultaneously the frequency signal of this oscillator generation a little less than, interference free performance is low.
Summary of the invention
The technical problem to be solved in the present invention is, improves sensitivity and the interference free performance of the oscillator that metal detection uses.
The technical scheme of technical solution problem of the present invention is to provide the oscillator that a kind of metal detector is used, the structure of this oscillator comprises, a comparison circuit that voltage signal is compared, one produces the initialization circuit of reference signal voltage, and one is converted to the change-over circuit of voltage by the inductance signal; Described comparison circuit consists of voltage comparator A1, inverter, and the output of voltage comparator is connected with the input of inverter, the output that the output of inverter is this oscillator; It is characterized in that, described initialization circuit consists of resistance R 1, R2, RF, the end of resistance R 1, R2, RF is connected with the voltage comparator inverting input, and the other end of resistance R 1, R2 is connected with power Vcc, power supply ground respectively, and the other end of resistance R F is connected with the output of inverter; Described change-over circuit consists of coil Lq, resistance R, and an end of coil Lq, resistance R is connected with the in-phase input end of voltage comparator, and the other end of coil Lq is connected with the output of inverter, another termination power ground of resistance R; Described initialization circuit forms reference voltage uj at the inverting input of voltage comparator, described change-over circuit forms at the in-phase input end of voltage comparator the inductance signal voltage ur changed exponentially, when inductance signal voltage ur is less than reference voltage uj, the output of inverter is high level Vog, when the inductance signal voltage is greater than reference voltage, the output of inverter is low level Vod, make oscillator export a square-wave signal uo, the inductance value l of the frequency of square-wave signal and the resistance r of resistance R and coil Lq
hRatio r/l
hBecome a proportional relationship.
With existing inductance, Capacitance parallel connection resonant oscillator, compare, at frequency of oscillation, inductance value, inductance variable quantity, respectively under equal condition, oscillator frequency side-play amount of the present invention exceeds one times than existing oscillator, has higher sensitivity; The signal output waveform of oscillator of the present invention is square wave simultaneously, and with sine wave signal ratioing signal amplitude stabilization, antijamming capability is strong; The line construction of oscillator of the present invention is simple, low cost of manufacture.
The accompanying drawing explanation
The circuit theory diagrams that Fig. 1 is first embodiment of the invention.
The circuit theory diagrams that Fig. 2 is second embodiment of the invention.
Oscillogram when Fig. 3 is circuit working of the present invention.
In Fig. 3, heavy line means the waveform of this oscillator output signal uo, and fine line means the waveform of inductance signal voltage ur, and dotted line means the waveform of reference voltage uj.
Embodiment
Existing accompanying drawings the specific embodiment of the present invention.
The oscillator that a kind of metal detector is used comprises, a comparison circuit that voltage signal is compared, and one produces the initialization circuit of reference signal voltage, and one is converted to the change-over circuit of voltage by the inductance signal; Described comparison circuit consists of voltage comparator A1, inverter, and the output of voltage comparator A1 is connected with the input of inverter, the output that the output of inverter is this oscillator; It is characterized in that, described initialization circuit consists of resistance R 1, R2, RF, the end of resistance R 1, R2, RF is connected with the inverting input of voltage comparator A1, and the other end of resistance R 1, R2 is connected with power Vcc, power supply ground respectively, and the other end of resistance R F is connected with the output of inverter; Described change-over circuit consists of coil Lq, resistance R, and an end of coil Lq, resistance R is connected with the in-phase input end of voltage comparator, and the other end of coil Lq is connected with the output of inverter, another termination power ground of resistance R; Described initialization circuit is to the inverting input input reference voltage uj of voltage comparator, described change-over circuit inputs to the in-phase input end of voltage comparator the inductance signal voltage ur changed exponentially, when inductance signal voltage ur is less than reference voltage uj, the output of inverter is high level Vog, when the inductance signal voltage is greater than reference voltage, the output of inverter is low level Vod, make oscillator export a square-wave signal uo, the inductance value l of the frequency f of square-wave signal and the resistance r of resistance R and coil Lq
hRatio r/l
hBecome a proportional relationship, that is:
F=k * r/l
h, f is frequency, k is a setting coefficient, relevant with the difference size of the high and low level of reference voltage uj.
In the first embodiment shown in Fig. 1, described voltage comparator A1 is an operational amplifier integrated circuit or voltage comparator integrated circuit, in the present embodiment, select the operational amplifier integrated circuit, its model is OP07, described inverter is that its model of inverter circuit A2 is CD4069, and the input of inverter circuit A2 is connected with the output of voltage comparator A1, the output that the output of inverter circuit A2 is oscillator.
In the second embodiment shown in Fig. 2, described voltage comparator A1 is the first voltage comparator in a pair of voltage comparator integrated circuit (its model is LM339), the output of voltage comparator A1 is connected to power Vcc by resistance R 5, the second voltage comparator A3 of described inverter in two voltage comparator integrated circuits, resistance R 3, R4, R6 forms, the inverting input of second voltage comparator A3 is connected with the output of the first voltage comparator A1, resistance R 3, the in-phase input end of the termination second voltage comparator of R4, resistance R 3, the other end of R4 connects respectively power Vcc, power supply ground, the output of second voltage comparator A3 is connected to power Vcc by resistance R 6.Resistance R 3, R4 provide a bias voltage for the in-phase input end of second voltage comparator A3, and this bias voltage is slightly larger than the low level voltage of inverter output.Inverter consists of stability and the carrying load ability of the output signal that can further improve oscillator voltage comparator in a second embodiment.
The stabilized voltage power supply that described power Vcc is output voltage+5V, for oscillator provides working power.
The operation principle of this oscillator is described referring now to the oscillogram of Fig. 3:
T0 section on time shaft: work as powered on moment, electric current in coil can not sport 0, no current in resistance R, inductance signal voltage ur is 0, reference voltage uj is greater than inductance signal voltage ur, the output of inverter is high level Vog, feedback by resistance R F is further raised reference voltage uj, and the value of reference voltage uj is 2/3 Vog, subsequently the Current rise in coil, also directly proportional rising of inductance signal voltage ur, the rising rule as shown in Equation 1:
ur＝Vog ×（1－e
-t/τ） （1）
In formula 1, the high level of Vog-oscillator output; The time that t-inductance signal voltage ur changes; τ-time constant; τ=l
h/ r, l
hFor the inductance value of coil, the resistance that r is resistance R.
T1 section on time shaft: when inductance signal voltage ur is greater than reference voltage uj, the output of inverter is low level Vod, feedback by resistance R F is dragged down reference voltage uj, the value of reference voltage uj is reduced to 1/3 Vog, electric current in coil descends subsequently, also directly proportional decline of inductance signal voltage ur, because the amplitude of low level Vod very I is considered as 0, so inductance signal voltage ur decline rule can mean by formula 2:
ur＝2/3 Vog ×（e
-t/τ） （2）
In formula 2, the high level that 2/3Vog is reference voltage uj.
T2 section on time shaft: when inductance signal voltage ur is less than reference voltage uj, the output of inverter is again high level Vog, and the feedback by resistance R F is raised reference voltage uj, and the value of reference voltage uj is 2/3 Vog, inductance signal voltage ur rises, and the rising rule means by formula 3:
ur＝ （Vog－1/3Vog）×（1－e
-t/τ）＋ 1/3Vog （3）
In formula 3, the low level that 1/3Vog is reference voltage uj.
T3 section on time shaft, the wave form varies situation is identical with the T1 section on time shaft, the T4 section on time shaft, the wave form varies situation is identical with the T2 section on time shaft, so analogizes, and known oscillator output signal uo is a square-wave pulse signal.
The inductance value l of the frequency f of the square-wave pulse signal of this oscillator and the resistance r of resistance R and coil Lq
hRatio r/l
hBecome a proportional relationship, that is:
F=k * r/l
h, k is a setting coefficient, relevant with the variation difference size of reference voltage uj, changes the larger frequency of oscillation of difference lower; Can set high level and the low level of reference voltage uj by the resistance of selecting resistance R 1, R2, RF.The amplitude of this oscillator output high level Vog is 4.5V, and when the resistance of resistance R 1, R2, RF equates, the high level of reference voltage uj, low level are set to respectively 2/3 and 1/3 of inverter output high level Vog, and setting coefficient k is 0.72; The resistance r of resistance R gets 560 Ω, the inductance value l of coil Lq
hGet 15mH, the frequency of oscillation of this oscillator is 27kHZ.The setting adjustment of the frequency of oscillator for convenience, the resistance of described resistance R F is made as adjustable.Described coil Lq is coiled into the coil of diameter 30cm, the number of turns 150 circles with wire diameter 0.49mm enamelled wire.
The LC oscillator that oscillator in existing metal detecting device is inductance, Capacitance parallel connection resonance, the expression formula of its frequency of oscillation f1 ' is:
f1’ ＝1 / [2π(l
h1’ × C)
1/2] （4）
L in formula 4
H1' be the winding inductance quantity of LC oscillator, the capacitance that C is electric capacity.
When the close metal of LC oscillator coil, its inductance value increases, and the inductance increment is Δ l
h', at this moment inductance value is l
H2', l
H2'=l
H1'+Δ l
h', the frequency of oscillation f2 ' of LC oscillator is:
f2’ ＝1 / [2π(l
h2’ × C)
1/2] （5）
Its frequency shift (FS) ratio is:
Δf’/ f2’ ＝(f2’ －f1’) / f2’
＝1 － (1+ Δl
h’/ l
h1 ’)
1/2
＝1 － (1+ 0.5Δl
h’/ l
h1 ’)
＝﹣0.5Δl
h’/ l
h1’ (6)
Formula 6 is at ratio (Δ l
h'/l
H1' (Δ l usually in the situation of)<=1
h' be less than l
H1') the approximate expression value that draws, the frequency offset that can have oscillator according to formula 6 is:
Δf’ ＝﹣0.5 f2’Δl
h’ / l
h1’ （7）。
The expression formula of the frequency of oscillation f1 of oscillator of the present invention is:
f1＝k r / l
h1 （8）
In formula 8, k is that a setting coefficient is relevant with the variation difference size of reference voltage uj, the resistance that r is resistance R, l
H1For the inductance value of coil Lq, set coefficient k and resistance R and be constant.
When the close metal of coil Lq, its inductance value increases, and the inductance increment is Δ l
h, at this moment inductance value is l
H2, l
H2=l
H1+ Δ l
h, the expression formula of the frequency of oscillation f2 of oscillator of the present invention is:
f2＝k r / l
h2 （9）
Its frequency offset is:
Δf＝f2－f1
＝(k r / l
h2) －(k r / l
h1)
＝k r [1/ (l
h1+Δl
h ) －1/ l
h1]
＝﹣[k r / (l
h1+Δl
h )] Δl
h / l
h1 (10)
Formula 10 is arranged, can be obtained:
Δf＝﹣f2Δl
h / l
h1 （11）。
At frequency of oscillation (f2, f2 '), inductance value (l
H1, l
H1'), inductance variable quantity (Δ l
h, Δ l
h') respectively under equal condition, formula 7 and formula 11 are contrasted, the frequency offset Δ f of known oscillator of the present invention exceeds one times than the oscillator frequency offset Δ f ' of prior art.It should be noted that the coefficient " 0.5 " in formula 7 is at ratios delta l
h'/l
H1' trend towards deriving in 0 situation, if ratios delta l
h'/l
H1' increase, the coefficient in formula 7 is less than 0.5.Therefore oscillator of the present invention is compared and is had higher sensitivity with the oscillator of prior art.
This oscillator can support the use with a frequency meter, because the output signal of this oscillator is square-wave pulse, therefore without this output signal is amplified, shaping, can directly connect the input of frequency meter.Because this vibration utensil has higher sensitivity, its investigative range is larger, when the coil of oscillator during away from metallic object, frequency meter display frequency f1, in the scope of 4 square metres, when the coil of oscillator is close to metallic object, gradual changes can occur in the frequency f 2 that frequency meter detects, and can position metallic object.
Claims (3)
1. the oscillator that metal detector is used, it comprises a comparison circuit that voltage signal is compared, and one produces the initialization circuit of reference signal voltage, and one is converted to the change-over circuit of voltage by the inductance signal; Described comparison circuit consists of voltage comparator A1, inverter, and the output of voltage comparator is connected with the input of inverter, the output that the output of inverter is this oscillator; It is characterized in that, described initialization circuit consists of resistance R 1, R2, RF, the end of resistance R 1, R2, RF is connected with the voltage comparator inverting input, and the other end of resistance R 1, R2 is connected with power Vcc, power supply ground respectively, and the other end of resistance R F is connected with the output of inverter; Described change-over circuit consists of coil Lq, resistance R, and an end of coil Lq, resistance R is connected with the in-phase input end of voltage comparator, and the other end of coil Lq is connected with the output of inverter, another termination power ground of resistance R; Described initialization circuit is to the inverting input input reference voltage uj of voltage comparator, described change-over circuit inputs to the in-phase input end of voltage comparator the inductance signal voltage ur changed exponentially, when inductance signal voltage ur is less than reference voltage uj, the output of inverter is high level Vog, when the inductance signal voltage is greater than reference voltage, the output of inverter is low level Vod, make oscillator export a square-wave signal uo, the inductance value l of the frequency of square-wave signal and the resistance r of resistance R and coil Lq
hRatio r/l
hBecome a proportional relationship.
2. the oscillator that metal detector according to claim 1 is used, it is characterized in that, described voltage comparator A1 is an operational amplifier integrated circuit, described inverter is an inverter circuit A2, the input of inverter circuit A2 is connected with the output of voltage comparator A1, the output that the output of inverter circuit A2 is oscillator.
3. the oscillator that metal detector according to claim 1 is used, it is characterized in that, described voltage comparator A1 is the first voltage comparator in a pair of voltage comparator integrated circuit, the output of voltage comparator A1 is connected to power Vcc by resistance R 5, the second voltage comparator A3 of described inverter in two voltage comparator integrated circuits, resistance R 3, R4, R6 forms, the inverting input of second voltage comparator A3 is connected with the output of voltage comparator A1, resistance R 3, the in-phase input end of the termination second voltage comparator A3 of R4, resistance R 3, the other end of R4 connects respectively power Vcc, power supply ground, the output of second voltage comparator A3 is connected to power Vcc by resistance R 6.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109981083A (en) * | 2019-03-19 | 2019-07-05 | 上海林果实业股份有限公司 | Waveform shaping circuit and electronic equipment |
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|---|---|---|---|---|
| US4323847A (en) * | 1979-06-11 | 1982-04-06 | Triple Dee Electronics Inc. | Oscillator type metal detector with switch controlled fixed biasing |
| CN86104310A (en) * | 1985-07-08 | 1987-01-07 | 戈林·克尔公司 | Metal detector |
| JPH05110412A (en) * | 1991-10-15 | 1993-04-30 | Omron Corp | Oscillator circuit and high frequency oscillation type proximity switch |
| EP1058094A2 (en) * | 1999-05-26 | 2000-12-06 | Matsushita Electric Works, Ltd. | Magnetic sensor |
| CN200959035Y (en) * | 2006-10-21 | 2007-10-10 | 孙锐钧 | Multifunctional metal detector with micro-inductor |
| US20090045813A1 (en) * | 2007-08-13 | 2009-02-19 | David Emery | Resonant pulse induction metal detector |
| CN101551469A (en) * | 2008-04-03 | 2009-10-07 | 鸿富锦精密工业（深圳）有限公司 | Metal detector |
-
2013
- 2013-08-29 CN CN201310381504.8A patent/CN103427764B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4323847A (en) * | 1979-06-11 | 1982-04-06 | Triple Dee Electronics Inc. | Oscillator type metal detector with switch controlled fixed biasing |
| CN86104310A (en) * | 1985-07-08 | 1987-01-07 | 戈林·克尔公司 | Metal detector |
| JPH05110412A (en) * | 1991-10-15 | 1993-04-30 | Omron Corp | Oscillator circuit and high frequency oscillation type proximity switch |
| EP1058094A2 (en) * | 1999-05-26 | 2000-12-06 | Matsushita Electric Works, Ltd. | Magnetic sensor |
| CN200959035Y (en) * | 2006-10-21 | 2007-10-10 | 孙锐钧 | Multifunctional metal detector with micro-inductor |
| US20090045813A1 (en) * | 2007-08-13 | 2009-02-19 | David Emery | Resonant pulse induction metal detector |
| CN101551469A (en) * | 2008-04-03 | 2009-10-07 | 鸿富锦精密工业（深圳）有限公司 | Metal detector |
Non-Patent Citations (1)
| Title |
|---|
| 张学勇 等: "一种金属探测器的设计", 《安徽建筑工业学院学报(自然科学版)》, vol. 15, no. 3, 30 June 2007 (2007-06-30) * |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109981083A (en) * | 2019-03-19 | 2019-07-05 | 上海林果实业股份有限公司 | Waveform shaping circuit and electronic equipment |
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Effective date of registration: 20211117 Address after: 276700 Zhongchuang space, Xingye street, economic development zone, Linshu County, Linyi City, Shandong Province Patentee after: Linshu Yixing steam supply maintenance service Co.,Ltd. Address before: 225500 C2-304 room, Kam do international garden, Jiangyan Town, Jiangyan District, Taizhou, Jiangsu. Patentee before: Gao Yuqin |