CN105785447A - Medium inductive channel target detection method - Google Patents

Abstract

The invention discloses a medium inductive channel target detection method. The method is realized by a plurality of parallel-plate capacitors. Two metal polar plates of each parallel-plate capacitor are arranged on the inside surfaces of a passageway parallelly and oppositely. A pedestrian passageway is divided into a plurality of spaces by all parallel-plate capacitors. According to the invention, the parallel-plate capacitors convert the medium change in the pedestrian passageway into a capacitance change, and the detecting result reflects a substantive characteristic of the medium. Because the capacitance change is detected, the detection method becomes simple, mature and reliable and the engineering installation requirement is lowered. The metal housing of a product can be sufficiently used to construct the parallel-plate capacitor in practical production and the production cost of the product is lowered. Because the pedestrian passageway is divided into a plurality of dependent spaces by the parallel-plate capacitors and the capacitance size of each space is corresponding to the medium characteristic of the space, so that the children and the luggage can also be detected and recognized effectively, which cannot be realized by an infrared light channel detection technology.

Description

A kind of medium vicarious channel targets detection method

Technical field

The present invention relates to electrolyte detection technique field, particularly relate to a kind of in the application of capacity plate antenna, the method that target current in walkway is detected.

Background technology

The application scenarios such as the gateway detection at such as station automatic fare collection, large stadium, infrared two-way emission type Air conduct measurement mode is applied in large quantities, generally multiple infrared tubes are arranged on the both sides of passage, when passage there being people pass through, have part pipe is blocked, by the rule blocked, controller just may identify which the size of the direction and goal volume of People's Bank of China.In concrete application process; to identify the volume of target exactly; being accomplished by arranging infrared receiving/transmission more closely to pipe, the operand of this cost that can increase equipment and controller, compromise consideration would generally be done between properties of product and product cost by manufacturer；Meanwhile, closely pipe can be caused interference by the infrared receiving/transmission of arrangement each other, increases the False Rate of equipment.The output signal of pipe is eventually connected to controller by the infrared receiving/transmission being distributed in passage both sides; multiple signals parallel transmission over long distances is not a good method; the controller of opposite side would generally be serially transmitted to again after first all signals of passage side being made state encoding; add intermediate connecting node, be unfavorable for the reliability of system；Infrared transmitter and the receptor of the integration in the commercially available infrared detection field that is specifically applied to have certain response speed, and when the pedestrian in passage quickly moves, system usually cannot detect the correct status of pedestrian.

In order to reduce adjacent infrared receiving/transmission influencing each other to pipe, generally carefully to adjust infrared receiving/transmission at the construction field (site) and to the setting angle of pipe or adopt extra light quarantine measures, generally cannot obtain desirable anti-jamming effectiveness.

Summary of the invention

It is an object of the invention to the deficiency existed for existing infrared two-way emission type Air conduct measurement mode, it is proposed that the current object detection method in walkway of a kind of space dielectric parameter detection.

It is an object of the invention to be achieved through the following technical solutions: a kind of medium vicarious channel targets detection method, the method is realized by multiple plane-parallel capacitors, and two metal polar plates of described plane-parallel capacitor are parallel just to the medial surface being positioned over passage；Walkway is divided into some spaces by all plane-parallel capacitors；By the change of the capacitance of plane-parallel capacitor in sense channel, obtain the relative dielectric constant of passage medium, thus realizing the detection of walkway target.

Further, described plane-parallel capacitor is driven by pulse signal.

Further, the frequency of described plane-parallel capacitor drive pulse signal is between 10kHz～10MHz.

Further, passage medial surface array fixes some plane-parallel capacitors, and the metal polar plate of plane-parallel capacitor is square, and walkway space uniform is split by all plane-parallel capacitors.

Further, described plane-parallel capacitor is as the frequency controlling elements of multi-resonant agitator, and when the medium character of plane-parallel capacitor changes, the output frequency of multi-resonant agitator can change accordingly.

Further, described multi-resonant agitator includes schmitt inverter, and plate condenser is connected with schmitt inverter by shielded cable.

Compared with prior art, the invention have the advantages that: the change of walkway medium is converted to the change of capacitance by plane-parallel capacitor, the result of detection embodies the substitutive characteristics of medium；Owing to being the change of detection capacitance, therefore detection means becomes simple, ripe, reliable, and project installation requires to reduce；In actual production, the metallic shell structure plane-parallel capacitor of product can be made full use of, reduce the production cost of product；Owing to walkway is divided into some independent spaces by plane-parallel capacitor, the capacitance size in each space all be correspond to the dielectric property in this space, therefore can also carrying out effective detection for child and luggage and identify, this is the infrared light Air conduct measurement irrealizable function of technology.

Accompanying drawing explanation

Fig. 1 is a kind of medium vicarious channel targets detection method schematic diagram；

Fig. 2 is based on the medium vicarious channel targets detection method circuit theory diagrams of Schmidt trigger；

Fig. 3 is the oscillogram of Schmidt trigger input and outfan.

Detailed description of the invention

The present invention being described in detail below according to accompanying drawing, the purpose of the present invention and effect will be apparent from.

A kind of medium vicarious channel targets detection method provided by the invention, the method is realized by multiple plane-parallel capacitors, and two metal polar plates of plane-parallel capacitor are parallel just to the medial surface being positioned over passage；Walkway is divided into some spaces by all plane-parallel capacitors.The detection of walkway target is converted into the detection of plane-parallel capacitor capacity by the present invention, infers the relative dielectric constant of passage medium by the change of capacitance in sense channel, thus effectively identifying the character of medium.

As it is shown in figure 1, to fix 15 pairs of plane-parallel capacitors in passage medial surface array, metal polar plate is square, and all metal plates are with S₁、S’₁, S₂、S’₂......S₁₄、S’₁₄, S₁₅、S’₁₅Numbering.Walkway space uniform is split by all plane-parallel capacitors.

For the capacitance of a plane-parallel capacitor, formula 1 determine:

$C={\mathrm{\ϵ}}^{\′}\×\frac{S}{d}$ (formula 1)

Wherein ε ' is the dielectric constant of medium between two pieces of pole plates of plane-parallel capacitor, and the right opposite that S is two pieces of pole plates of plane-parallel capacitor amasss, and d is the distance between two pieces of pole plates of plane-parallel capacitor.

When medium when between pole plate is vacuum, it is called permittivity of vacuum ε₀(or permittivity of vacuum), ε₀=8.854 × 10^-12F/m.With permittivity of vacuum for benchmark, other dielectric permittivity is called relative dielectric constant ε relative to the ratio of permittivity of vacuum, i.e. ε '=ε × ε₀, formula 1 can be expressed as:

$C=\mathrm{\ϵ}\×{\mathrm{\ϵ}}_0\×\frac{S}{d}$ (formula 2)

The relative dielectric constant of some Common materials of nature is as shown in table 1.

The relative dielectric constant of table 1 Common materials

Material	Relative dielectric constant	Material	Relative dielectric constant	Material	Relative dielectric constant
						Vacuum	1	Hard rubber	4.3	Paraffin wax	2.0～2.1
Air	1.000585	Rubber	2～3	Paper	2.5
						Water vapour	1.00785	Wood	2.8	Sal	7.5
Hydrogen sulfide	1.004	Yellow phosphorus	4.2	Muscle	66.2
						Water	81.5	Glass	4.1	Fat	12.7
Ice	3～4	Marble	6.2	Bone	2
						Glycerol	45.8	Granite	8.3

Owing to most of composition of tissue is water, also having various ionic species, relative dielectric constant significantly high (relative dielectric constant of water is 81.5), these materials make human body become good electric conductor.When detecting the frequency difference of signal, the relative dielectric constant slightly difference of each tissue.Such as: when frequency is 100kHz, the relative dielectric constant of muscle is 66.2, the relative dielectric constant of fat is 12.7；When frequency is 400kHz, the relative dielectric constant of muscle is 58.0, and the relative dielectric constant of fat is 11.6；When frequency is 900kHz, the relative dielectric constant of muscle is 56.0, and the dielectric constant of fat is 11.3.Visible, when frequency is relatively low, the value of relative dielectric constant is somewhat larger.

For a pair capacitor plate S shown in Fig. 1₁、S’₁, it is assumed that its area is 0.1m², relative distance d₁For 0.5m, the capacitance obtained under its normal temperature air state can be calculated according to formula 2 and be about 1.8pF.

Generally, the composition that human body is respectively organized is as shown in table 2, according to the numerical value shown in table 2, can calculate the equivalent relative dielectric constant obtaining human body and be about 64.1.

The composition of table 2 tissue

When human body is in the passage shown in Fig. 1, the material proportion composition in passage can be changed.With the capacitor plate S in Fig. 1₁、S’₁For example, work as S₁、S’₁Area be 0.1m²Time, its length of side is 0.33m, S₁、S’₁Between space be 0.05m³, the volume (adult) of human body is about 0.06m³, when human body is in S₁、S’₁Between time, take S₁、S’₁Between space be(assuming that the height of people is 1.75m), now S₁、S’₁Between the equivalent relative dielectric constant of medium be $64.1\×\frac{0.0113}{0.05}+\frac{(0.05-0.0113)}{0.05}\×1.0006=15.26,$ According to formula 2, now plane-parallel capacitor S₁、S’₁Capacitance be 27.04pF.

Visible, when human body enters S₁、S’₁Between space time, plane-parallel capacitor S can be caused₁、S’₁Capacitance change from 1.8pF to 27.04pF, capacitance increase 15 times, electric capacitance change is obvious.

Embodiment, based on the medium vicarious channel targets detection method of Schmidt trigger

As shown in Figure 2, medium vicarious channel targets detection method based on Schmidt trigger, adopt the Digital Logic integrated circuit 74HC14 with Schmidt trigger circuit as main circuit devcie, Schmidt trigger circuit has voltage identification function, when the voltage of input exceedes forward threshold level V_T+Time output low level, when the voltage of input is lower than negative sense threshold level V_T-Time output high level, V_T+And V_T-Between have a voltage difference, be called threshold voltage V_H.When supply voltage difference, even same chip, V_HAlso differ.Table 3 illustrates the voltage-transfer characteristic of high-speed cmos Schmidt hex inverter 74HCl4, lists when supply voltage is the threshold voltage of Schmidt trigger in tri-kinds of situations of 2.0V, 4.5V, 6.0V.Generally, our power supply is all select V_CC=5V, the electronic system to ensure us can compatible TTL logical signal.When supply voltage is 5V, actually measured threshold voltage is as follows:

Output logic high level V_OH=5.0V

Output logic low level V_OL=0.0V

Forward threshold level V_T+=2.5V

Negative sense threshold level V_T-=1.5V

The voltage-transfer characteristic (25 DEG C) of table 374HCl4

For each schmitt inverter shown in Fig. 2, all constitute an astable multivibrator with its peripheral circuit, one pole plate of input termination plate condenser, another pole plate ground connection of plate condenser, considering the requirement of actual installation, plate condenser is connected with schmitt inverter by shielded cable.Below with plate condenser S₁、S₁' operation principle of circuit is described for example.

When the circuit is energized, plate condenser S₁、S₁' and electric capacity C₁In there is no electric charge (plate condenser S₁、S₁' and electric capacity C₁It is connected in parallel), therefore schmitt inverter IC_1AInput terminal voltage be 0, the voltage of its outfan is high level (i.e. supply voltage V_CC), therefore plate condenser S₁、S₁' and electric capacity C₁By V_CCBy resistance R₁Charging, its voltage u_CChanging Pattern be:

$u_C\left(t\right)=V_{CC}(1-e^{-\frac{t}{R_{1}C}})$ (formula 3)

Wherein:

u_CT () is elapsed time t rear plate capacitor S₁、S₁' and electric capacity C₁The magnitude of voltage at two ends.

V_CCFor capacitor initial voltage and difference (i.e. supply voltage) between voltage after reaching steady statue.

E is the radix (2.718) of natural logrithm.

T is the charging interval of capacitor.

R₁, resistance, unit is ohm.

C, plate condenser S₁、S₁' and electric capacity C₁Capacitance sum, unit is farad.

When the voltage at capacitor two ends is charged to VT+, schmitt inverter IC1A outfan becomes low level (i.e. 0V), now plate condenser S1, S1 ' and electric capacity C1 resistance R1 electric discharge, its voltage u_CChanging Pattern be:

$u_C\left(t\right)=V_{T+}{e}^{-\frac{t}{R_{1}C}}$ (formula 4)

When the tension discharge at capacitor two ends is to V_T-Time, schmitt inverter IC_1AOutfan is become high level from low level (i.e. 0V), now plate condenser S₁、S₁' and electric capacity C₁Again by V_CCBy resistance R₁Rule charging shown in formula 3, IC_1AThe time t of output low level_OLAs follows:

$t_{OL}=R_{1}C\ln \left(\frac{1}{1-\frac{V_{T+}-V_{T-}}{V_{T+}}}\right)=R_{1}Cln\left(\frac{1}{1-\frac{1.0V}{2.5V}}\right)=0.5108R_{1}C$ (formula 5)

As plate condenser S₁、S₁' and electric capacity C₁The voltage at two ends is from V_T-Rule shown in formula 3 is charged to V_T+Time, schmitt inverter IC_1AOutfan becomes low level (i.e. 0V), IC from high level again_1AThe time t of output high level_OHAs follows:

$t_{OH}=R_{1}Cln\left(\frac{1}{1-\frac{V_{T+}-V_{T-}}{V_{CC}-V_{T-}}}\right)=R_{1}Cln\left(\frac{1}{1-\frac{1.0V}{3.5V}}\right)=0.3365R_{1}C$ (formula 6)

IC_1AThe waveform of input and outfan is as shown in Figure 3.

IC_1AThe cycle T of output pulse:

T=t_OH+t_OL=0.3365R₁C+0.5108R₁C=0.8473R₁C (formula 7)

IC_1AThe frequency f of output pulse:

$f=\frac{1}{T}=\frac{1}{0.8473R_{1}C}=\frac{1.18}{R_{1}C}$ (formula 8)

By formula 8, can obtain(formula 9)

As long as therefore IC measured by controller_1AThe frequency of output pulse, whether through type 9 just can calculate the equivalent capacity of walkway, thus judging the dielectric property of walkway, it is judged that have pedestrian to pass through on current walkway.

The invention provides a kind of medium vicarious channel targets detection method, the change of walkway medium is converted to by plane-parallel capacitor the change of capacitance, detection means is simple, ripe, reliable, and project installation requires to reduce；Walkway is divided into multiple independent space, the capacitance size in each space all be correspond to the dielectric property in this space, therefore can also carry out effective detection for child and luggage and identify.

A kind of medium vicarious channel targets detection method that the present invention describes; described details is only preferably embodiment; but it is not intended to be limited to this; its embodiment is also not restricted to the described embodiments; other any based on the change made under the principle of the invention, modification, combination, simplification; it is accordingly to be regarded as the substitute mode of equivalence, is all contained within protection scope of the present invention.

Claims (6)

1. a medium vicarious channel targets detection method, it is characterised in that the method is realized by multiple plane-parallel capacitors, two metal polar plates of described plane-parallel capacitor are parallel just to the medial surface being positioned over passage；Walkway is divided into some spaces by all plane-parallel capacitors；By the change of the capacitance of plane-parallel capacitor in sense channel, obtain the relative dielectric constant of passage medium, thus realizing the detection of walkway target.

2. a kind of medium vicarious channel targets detection method according to claim 1, it is characterised in that described plane-parallel capacitor is driven by pulse signal.

3. a kind of medium vicarious channel targets detection method according to claim 2, it is characterised in that the frequency of described plane-parallel capacitor drive pulse signal is between 10kHz～10MHz.

4. a kind of medium vicarious channel targets detection method according to claim 1, it is characterized in that, passage medial surface array fixes some plane-parallel capacitors, and the metal polar plate of plane-parallel capacitor is square, and walkway space uniform is split by all plane-parallel capacitors.

5. a kind of medium vicarious channel targets detection method according to claim 1, it is characterized in that, described plane-parallel capacitor is as the frequency controlling elements of multi-resonant agitator, and when the medium character of plane-parallel capacitor changes, the output frequency of multi-resonant agitator can change accordingly.

6. a kind of medium vicarious channel targets detection method according to claim 5, it is characterised in that described multi-resonant agitator includes schmitt inverter, and plate condenser is connected with schmitt inverter by shielded cable.