BLOG: What is PCAP technology?

23. 10. 2019

PCAP touch screen is the type of display that uses projected capacitive technology. It is one of the most common types of touch screen technology, and currently, it is the first option for most of the smartphones, tablets, and other small-medium sized devices equipped with a touch sensor. 

How does PCAP technology work? 

Mutual Capacitance

When we talk about PCAP, we usually mean mutual capacitance technology, which applies the phenomenon that most conductive objects can carry a charge if they are very close together. The touch panel is composed of a grid (array) where it consists of an X by Y array of traces, forming X*Y units of capacitors. It generates a mutual capacitance between the elements of the columns and rows. The controller measures each node independently, changing the distortion of the electric field of the touch position. Thus, it can detect more than one simultaneous touches and does not cause the ghost touches problem.

Self-capacitance

The self-capacitance technology is based on measuring the capacitance of a single electrode concerning ground. When the finger gets close to the electrode, the human-body capacitance changes the self-capacitance of the electrode, and the controller detects the touch. It is usually constructed from two layers of electrodes arranged in a layer of rows and columns, where the intersections represent unique touch coordinates pairs. It works great with a single touch, but if you touch the screen on the two different locations, the changes in the self-capacitance of the electrodes create four various intersections, and thus controller detects four different touchpoints. Therefore, the more popular and more used one is the mutual capacitance PCAP.