|Resistive Touch |
The resistive touchscreen consists of a glass panel with a resistive coating plus a coversheet with a conductive coating. The two layers are separated by tiny insulating dots.
When the screen is touched, the coversheet flexes to make electrical contact with the coating on the glass. The controller alternately drives the X and Y axes on the glass layer with a +5V current and reads the resulting voltage from the cover sheet, which is the analog representation of the position touched.
Surface capacitive technology consists of a uniform conductive coating on a glass panel. Electrodes around the panel's edge evenly distribute a low voltage across the conductive layer, creating a uniform electric field. A touch draws current from each corner. The controller measures the ratio of the current flow from the corners and calculates the touch location.
Surface Acoustic Wave (SAW) Touch
The Surface Acoustic Wave (SAW) touchscreens consist of a glass overlay with transmitting and receiving piezoelectric transducers for the X and Y axes.
The controller sends a five-megahertz electrical signal to the transmitting transduce, which converts the signal into ultrasonic waves within the surface of the glass. These eaves are directed across the touchscreen by an array of reflectors. Reflectors on the opposite side gather and direct the waves to the receiving transducer, which reconverts them into an electrical signal. The process is repeated for each axis.
When you touch the screen, you absorb a portion of the waves traveling across it. The received signals for X and Y are compared to the stored digital maps, the change is recognized, and a coordinate is calculated.
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