By ADMetro In
, Posted
Waterproof Touch Screens

PCAP or ULTRA Resistive: Which Touch Screen is Ideal for Waterproof Solutions?

With the ever-increasing demand for waterproof solutions in touchscreen applications, manufacturers are focused on evolving related technology to provide the best solutions. The literal meaning of waterproof gives the sense that the touch screen would be able to work reliably under water for a significant period. But it is not as simple as it sounds. When it comes to touch sensors, they can be described better as water resistant.

Waterproof touch screens refer to the sealed sensor face and housing that prevent dust, dirt and moisture. The device seal quality is, typically, identified through Ingress Protection (IP) rating such as IP-67, which is a common standard. But a good seal does not mean the device will work underwater.

A D Metro understands this gap between waterproof and water resistant and thus offer two primary touch screen solutions:

  • Projected Capacitive (PCAP) Touch Screen
  • ULTRA Resistive Touch Screen

Both these touch screens come with distinctive features and provide specific solutions as required by the applications. Hence, the answer to “which touch screen is better for waterproof solution” totally depends on what feature – waterproof or water resistant. Which of these are you are looking to integrate into the touch application.

So how to decide which touch screen will be ideal to use with a particular application? The following is the waterproof feature of PCAP and ULTRA Resistive touch technology explained.

Projected Capacitive (PCAP) Touch Screens
PCAP touch sensor construction encloses several “channels”, placed in separate X and Y configurations to form a grid. These channels are made of transparent conductive coating on film or glass plates. A PCAP touch sensor typically works by sending Radio Frequency (RF) through each of the channels on one axis of the grid.

So the RF mechanism itself makes the waterproof limitation obvious for PCAP touch screens. RF is just another form of electricity, and water is a fair conductor of electricity. It provides conductive paths for RF. When there is a significant amount of water on the surface of the PCAP touch sensor, it can result in the coupling of X and Y channels, just like a finger touch, causing the sensor to activate without human touch. Additionally, when you touch one spot on the screen surface, water can couple that spot with another one on the screen, causing erratic operations.

However, a smaller amount of water like mist or small droplets usually does not affect the operation. In fact, water droplets less than 4mm do not hinder operations on the PCAP touch screen.

So, there is nothing like waterproof PCAP operation. But A D Metro provides a few signal processing techniques that can help address the water-related issues in PCAP touch screens to some extent.

  • Water Rejection- controller is programmed to reject inputs from the sensor until it finds something similar to normal touch. This technique ensures the touch screen will not falsely activate when wet.
  • Wet Tracking- controller is programmed to ignore the amount of RF leakage.

Moving to the next touch technology that is in line with the several innovations by A D Metro.

ULTRA-Resistive Touch Screen
When it comes to operating a touch sensor underwater, it is only A D Metro’s patented ULTRA Resistive Touch Screen you can rely on. It’s a thin glass-faced resistive touch sensor that is completely immune to water exposure. The ULTRA Resistive touch screen sensor is constructed with a micro-thin sheet of borosilicate glass that is laminated to an indium tin oxide (ITO) coated polyethylene terephthalate (PET) top sheet. This innovative design makes the external glass layer water and moisture-proof and not just moisture resistant.

Unlike PCAP touch screen, ULTRA Resistive is a pressure-activated touch screen sensor, which means it is independent of electrical changes in capacitance for operations and eliminates the chances of false coupling or touch.

Given the above discussion, it becomes clear that for an application requiring to work flawlessly underwater or with a considerably wet surface, A D Metro’s ULTRA Resistive touch screens will be the ideal waterproof touch screen solution. But, in case you need multi-touch sensors, A D Metro has a line of PCAP products, including its own controller enabled with water rejection and wet tracking capability that you can consider for waterproof touch screens.

However, A D Metro has also elevated the function of ULTRA Resistive touch screens through the innovation of a 2-touch resistive controller. This state-of-the-art controller allows multi-touch operations using ULTRA-Resistive touch screens, making it the most preferred selection for rugged and waterproof applications.


Ask the touch screen experts at A D Metro