What is the simple principle of screen of mobile phone capacitance?

We are using the electronic device that touchs screen everyday, for instance computer of mobile phone, flat. Does everybody know what the working principle that touchs screen is? The place that how knows our hand points to is it? Why the mobile phone stuck film to be able to be used euqally, and taking a glove to cannot be used normally?

Current, the feeling screen majority that uses on market is screen of capacitance mood feeling. To understand its working principle, we explain what capacitance is above all.

1745, holand Lai pauses college professor Masenbuluoke invented Lai to pause bottle, with will store charge.

Lai pauses the fundamental of bottle is: The metallic bar that passes an electric conduction and metallic chain guide charge in bottle, bottle inside and outside is stuck respectively have tinsel. Such, charge can store in bottle. We know now: Guide when positive electrical charge when going up into the tinsel in bottle, if ground connection of tinsel of the side outside bottle, on tinsel of the side outside waiting for the negative electric charge of the quantity to be able to be attracted. negative electric charge is attracted each other, but because vitreous bottle is dielectric, block up their neutralization, so charge stores came down.

1752, the cacique of American absolute war, the rich Lan Kelin that imprints on 100 yuan of US dollar uses Lai to pause bottle was done famous " kite experiment " , use kite entered thunder conductance of the sky Lai to pause in bottle, the report on the lightning that proved the sky and ground is same kind of material.

Actually, should store charge, do not need bottle certainly. As long as two are isolated from each other and close conductor can have similar action, we say for capacitor. The simplest capacitor is smooth andante capacitor. two plate each other are stood by, a plate carries positive electricity, another plate carries negaive electricity, as a result of the attraction between charge action, the circuit outside wanting two electrode to was not passed only connects, charge won't run.

Insulation is in the center of capacitor, theoretic say electric current is to cannot pass capacitor. But, in the process that capacitor charges and discharges, volume of the charge on capacitor plate can have change, can be being regarded is electric current passed capacitor.

For instance, we will be original not electrified capacitor and batteries are polar and conterminous, capacitor can charge, namely positive electrical charge swarms into capacitor go up plate, negative electric charge swarms into next plate of capacitor. In circuit besides capacitor between two plate outside the part, others has electricity, voltaic direction regulation is the direction with directional and mobile positive electrical charge, so we can say, the charging current of suitable hour hand appeared in circuit. This electric current is the instant, when the voltage of the voltage of capacitor and batteries is identical, electric current disappeared. Be similar to to connect implement, original and left water is higher, water can flow. When two side water is euqally high, surface flowed no longer.

After filling report when capacitor, although we disconnect power source, the charge on capacitor also won't disappear. But, if we capacitor two plate are linked together directly with lead, the access that negative electric charge found to be able to be counteracted, then, positive electrical charge and negative electric charge can be counteracted through this access, anticlockwise electric current appears in circuit, this electric current calls discharge electric current. Discharge electric current also is the instant, charge is counteracted after ending, discharge electric current disappeared.

If capacitor undertakes charge and discharging repeatedly, charging current and discharge electric current can appear repeatedly in circuit, and the direction of charging current and discharge electric current is contrary. This kind of electric current is the alternating current that has told before us. We knew now, alternating current can pass capacitor.

We know, test pencil is to be able to measure a lead electrified. Whether had you thought, if stand on the chair to contact live wire with test pencil, can test pencil shine?

Because person and earth are conductor, and the chair is dielectric, and family expenses report is alternating current, because this can pass capacitor, although stand on the chair to touch front line with test pencil, test pencil still can be measured, express to still electric current passed test pencil and human body. Just this electric current is smaller, human body does not have what feeling.

We can explain capacitance feels screen principle eventually now. Simple capacitance screen is 4 compound glass board, have layer ITO stuff among them. ITO is material of stannum of indium of a kind of oxidation, it is transparent, and OK and electric, agree with production feeling screen.

When finger contacts on screen a certain place, make coupling capacitor with respect to meeting and ITO material, change the capacitance volume that contact handles. 4 horn of screen can have lead, because alternating current can pass capacitor, the electric current of 4 lead can run quickly to contact, and voltaic size and the distance to contact are concerned. The chip of mobile phone interior can analyse the electric current of 4 horn, pass computation to be able to get the seat of contact.

More careful capacitance screen is screen of projectile style electric capacity. It uses the ITO array that is illuminated by corrode, these ITO layers form many levels and perpendicular electrode through corrode of eat by moth. The ITO component of each part also is contained conduct feeling function.

When finger feels a certain place, undertake coupling with array capacitance, changed the electric field on screen, through sensor and chip analysis electric circumstance electric current changes, can feel contact position. Before comparing Yu Zhi quadrilateral voltaic capacitance screen, screen of this kind of capacitance can realize much dot to touch accuse, application is more wide.

The person's finger is conductor, ability can affect capacitance screen, and screen of capacitance of lay a finger on of use insulation material does not have a law to operate a mobile phone. The mobile phone sticks film to also can be used, because finger and ITO layer also do not need to contact originally,this is, intermediate itself has vitreous insulation layer, the action that sticks insulation film just is equivalent to glass thick little, electric current still can have shed the capacitor that the conductor place in finger and screen forms. Nevertheless, if the glove is too thick, the conductor be apart in the finger when lay a finger on touchs screen and screen too far, electric capacity is smaller, can't be felt by sensor, wearing muffler so cannot operate a mobile phone.

Actually, capacitance sensor still has a lot of in the life, wait than using the toilet the common automatic strong water unit, automatic dry mobile phone in place, a lot of it is to had used capacitance to pass of feeling. When human body is stood by or leaving formerly, the capacitor that human body and device make produced change, sensor feels this kind of change, control circuit has some kind of operation.

Sensor is in the life, it is nowhere is absent simply!