The Relationship between Activation Force and Sensitivity for A Resistive Touch Screen

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A resistive touch screen operates by the "force" applied on it. PenMount occasionally receives requests from customers asking if it is possible to adjust the sensitivity of a resistive touch screen through the controller. To this question, we'd like to raise another question in reply: what has decided the sensitivity of a resistive touch screen? Is it the controller or the touch screen? In this issue of PenMount Bulletin, we will make it clarified that the operation of a resistive touch screen actually depends on its constituent materials and its design.

A touch screen operates by the force applied on it. The force that makes the touch screen work is the so called "sensitivity" of a touch screen. In the following, we will detail "sensitivity" in three phases :

1. See the figure below. It shows the state before force is applied to the touch screen. The finger is simply placed on the touch screen. The finger contacts the touch screen surface, but ITO film and ITO glass haven't contacted each other. No action is triggered since the two electrical conductive layers aren't pressed together and no voltage gradient is caused.

2. When force is gradually applied to the touch screen, the upper ITO film layer is pressed but isn't fully pressed to the bottom ITO glass, and therefore the ITO film and ITO glass are only slightly contacting each other (due to uneven force application). The rise and fall of resistance are great at this moment. This is the moment when signals haven't reached stability, and also the moment some users might mistakenly think as a time to adjust the sensitivity. We'd like to clarify that if the controller receives and sends out these unstable signals, the touched position detected will be wrong. However, PenMount has overcome such problem by filtering the unstable signals when signals haven't got stable yet.

3. When the force applied increases to certain extent, say 10 g or more, the ITO film and ITO glass are steadily contacted and signals are stable. The controller receives normalized signals.

A regular touch on the touch screen is usually a combination of the 3 phases mentioned above. For example, the line drawn on the touch screen with your finger pulp breaks easily. This is mainly due to 2 reasons. On one hand, your finger pulp, the contact area, is big. The bigger the contact area is, the smaller the pressure is. On the other hand, the angle of your operating finger isn't always consistent. Whether due to the incomplete contact between ITO glass and ITO film as mentioned in (B) or due to lack of contact between ITO glass and ITO film as mentioned in (A), PenMount drivers ensure you the best touch experiences by the optimized sensitivity of the touch screen.

PenMount series of touch software and hardware are designed to meet market demands. If customized specifications are needed, we are always ready and available to help customer to complete their project. For more PenMount controllers and drivers information,  contact Omni Display