Making the First Capacitive Touchscreen Meet Waterproofing Needs

Since before the introduction of the first capacitive touchscreen, exposure to water and moisture has posed problems for most electronics. That is until manufacturers started coming up with efficient waterproofing methods. Moisture and water causes damage to electronics and make operation of such devices in wet environments that much harder.

International Waterproofing Standards

Still, it would be wrong for companies to simply brand their products as waterproof. This is why there are international standards set for waterproofing. According to the International Electrotechnical Commission (IEC), devices that can be classified as waterproof must meet high Ingress Protection (IP) ratings. The highest achievable is IP-67 and such devices can be immersed in water up to 1m as well as handle exposure to dust.

Water Rejection and Wet Finger Tracking

There are primarily two subset definitions of waterproofing: water rejection and wet finger tracking. Water rejection is defined as the capacitive touch screen’s ability to reject false touches from occurring when liquid makes contact with the screen. At the same time, the screen should recover once the liquid has been removed.

Wet finger tracking, on the hand, refers to the touch screen’s capacity to track the position of a user’s finger even with the presence of water. It is well known that water on the screen affects the accuracy of touch when the screen is wet, and true waterproof screens will always maintain accuracy. The ideal number for tracking requirement in the presence of water is generally 1-2 mm.

Explaining Water Physics

Capacitive touch screen technology works through conductive touch. Because water is also conductive, this will make it more difficult for operation. To remedy this, waterproof touch screens make use of “self-cap” physics that allows the screen sensors to apply excitation signals to accurately sense the amount of charge it takes for the receiver.

Source:

The Basics of Waterproofing Capacitive Touchscreens, EE Times
Making Capacitive Touch Sensors Water Tolerant, Embedded

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