It can be measured to accurately determine the exactly touch location.Īll projected capacitive touch (PCT) solutions have three key features in common:Īpplying voltage to the array creates a grid of capacitors.īringing a finger or conductive stylus close to the surface of the sensor changes the local electrostatic field, the electronic circuit sees a capacitor formed by the activated electrode “x” and the series facing electrode “y” with the capacity of the human body. The capacitance can be changed at every individual point on the grid (intersection). If another conductive object, in this case a finger, bridges the gap, the charge field is interrupted and detected by the controller.Īll PCT touch screens are made up of an electrode – a matrix of rows and columns. As the human finger (is also a conductor) touching the surface of the screen results in a distortion of the local electrostatic field, measurable as a change in capacitance.Now PCT used mutual capacitance, which is the more common projected capacitive approach and makes use of the fact that most conductive objects are able to hold a charge if they are very close together. Foil 1.2 Projected Capacitive Touch (PCT)Ī PCT screen consists of an insulator such as glass or foil, coated with a transparent conductor – sensing (Copper, ATO, Nanocarbon or ITO).Glass window (integrated in glass sheet).Does not immune to electromagnetic interference.Touch detection does not happen before physical contact with the screen.Cannot be used on curved surfaces (flex).Does not require a construction area behind the screen.Surface coating overlays are not necessary.Does not requires periodic recalibration.Unaffected by moisture, rain or temperature.
#Ftir multitouch screen free
The sensor’s controller can determine the location of the touch indirectly from the change in the capacitance as measured from the four corners of the panel.Ĭapacitive touchscreens provide: accurate drift free operation that is unaffected by temperature, humidity and can be operated by gloved fingers even in battery powered equipment. When a conductor, such as a human finger, touches the uncoated surface, a capacitor is dynamically formed. A small voltage is applied to the layer, resulting in a uniform electrostatic field. In this basic technology, only one side of the insulator is coated with a conductive layer. As the human body is also a conductor, touching the surface of the screen results in a distortion of the local electrostatic field, measurable as a change in capacitance. Frustrated Total Internal Reflection (FTIR) / Diffused Surface Illumination (DSI)įorce-Based Sensing 1 Capacitive Technology 1.1 Surface Capacitive TechnologyĪ capacitive touch screen panel consists of an insulator such as glass, coated with a transparent conductor.Infrared Grid Technology (opto-matrix) / Digital Waveguide Touch (DWT)™ / Infrared Optical Waveguide.
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