Resistive Multi-Touch Technology
Conventional resistive touch screens are unable to detect more than one contact at one time whether it concerns a 4-, 5-, or 8-wire. In 2008, AMT broke through this limit by presenting Multi-Finger to the market. MF makes it possible to detect and track up to 12 contacts on a touch screen at one time. However, starting from last year, you might have heard about other resistive technology that supports multi touch input, they are the AMR (Analog Matrix Resistive) and DMR (Digital Matrix Resistive) touch screens. They are both developed based on 4-wire resistive technology. In this issue of AMT news express, we will share with you the advantages and disadvantages and also the applications of these resistive touch screens (whether dual-touch or multi-touch).
Let's start with the touch theory of AMR and DMR. AMR and DMR are both constructed based on the standard 4-wire resistive structure. The coordinate axes X and Y are laid out onto each upper and bottom transparent electrically conductive film (ITO Film) and conductive glass (ITO Glass). The upper and bottom electrodes are separated by many dot spacers between them. When we apply force to the upper electrode with a finger, stylus, or other medium, the two electrical conductive layers are pressed together and voltage gradient is caused, and signals indicating voltage change are sent to controller through buses, so that controller can calculate the coordinates of the position that is touched.
For AMR touch screens, X and Y coordinates are laid out to the electrically conductive layers by the interval of about 1 cm. These coordinates form a lot of zones when the upper and lower layers are stacked together. Each zone is a 4-wire resistive touch area, after we apply force to these zones with our fingers, styli or other media, signals are sent to the controller, then the controller can calculate the coordinates of the touched position according to the proportion of the voltage dropped. As to the question how many touches can be operated simultaneously, it depends on the speed of the controller.
DMR divides the touch screen to even smaller zones, it is divided by 1mm~3mm intervals. When a zone is touched, it will be activated to work similarly to an ON/OFF switch. Then the digital signal indicating ON or OFF is sent to the controller. The controller will calculate the coordinates of the position touched.
Unlike DMR and AMR, AMT's Multi-Finger is developed based on 5-wire resistive touch technology. Its upper conductive film (ITO Film) is divided to multiple zones. As each touch zone functions like an individual analog touch screen of single touch input, the entire touch screen accepts simultaneous multiple touches. A Multi-Finger touch screen can be divided to 2 zones or up to 12 zones with each zone size and zone position definable by customer's application.
AMR and DMR share the advantage that touch zones can be made very small so that software applications have more flexibility. However, the applications are more practical for small-sized products due to material readiness and production complexity. MF, on the contrary, although has less touch zones than AMR or DMR, it requires much less circuit lines than AMR or DMR and is therefore a good choice for products of bigger sizes or for the products with defined software application, such as the industrial use to reconfirm safety.
MF is currently in mass production, sizes available from 3" to 22". Each touch zone size and zone position is definable for you. We'd be happy to discuss with you about developing the appropriate MF touch screens for your products. Should you have any question and requirement for MF products, please contact Omni Displays LLC.
Advance to the future with Omni Displays touch solutions.
