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My experience is that when I'm running, my fingers "don't work" on my phone screen.

My understanding was that the sensor on a touch screen works on static-charge, ie that you act as an 'earth' to the screen and it can sense the difference in charge.

Surely sweat on your finger would increase the conductivity of electric current?

My question is: Why does a sweaty finger neutralise the touch-sensor on my phone screen?

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    \$\begingroup\$ It never does on mine, maybe your phone is crappy? \$\endgroup\$ – PlasmaHH Apr 16 '15 at 11:34
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Most phone screens are capacitive. They work by sensing the change in capacitance due to a nearby conductive object.

I can't imagine a way in which simply having some sweat on a fingertip would interfere with this mechanism. I can't reproduce the problem with my phone and a glass of salty water.

However, I'll offer a guess as to what's happening: if you get enough sweat on the screen, the phone will have difficulty distinguishing what is a finger, and what is a gob of sweat. To the phone, broad contact over large areas of the phone look a lot like the side of your face, so the phone ignores these touches since mashing keys with your face is usually not desirable.

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    \$\begingroup\$ I believe your guess is wrong, since phones have proximity sensors to avoid hanging up the call with your face or taking photos with your ear while you talk. Large amount of sweat on the screen can nevertheless reduce response accuracy to the point where the user will think it doesn't work anymore. \$\endgroup\$ – Dmitry Grigoryev Apr 16 '15 at 13:12
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    \$\begingroup\$ @DmitryGrigoryev Not all phones are far as I know, I think some have face touch detection... \$\endgroup\$ – Tim Apr 16 '15 at 18:56
  • \$\begingroup\$ Cypress touch sense controllers advertise face detection. They also advertise sweat immunity, so it seems this is an issue on the minds of manufacturers \$\endgroup\$ – regdoug Apr 16 '15 at 20:53
  • \$\begingroup\$ Apart from using a proximity-sensor to ignore accidental touch events, another common method used to detect accidental touches is to ignore any touch event that is part of a large block/area. This method eliminates cases where the cheek/palm-rest comes in contact with the touch-screen of a phone or tablet. \$\endgroup\$ – TheCodeArtist Apr 20 '15 at 9:14
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I've experienced your problem too. My hands sweat a little bit more than average, and while my phone screen is 'wet' its ability to tell my actions touch/swipe diminish. So, I just tested this on my Samsung S3 (which has a capacitive touch screen).

All it took for this problem to arise was sparkling some water on its screen and trying to do any actions like going back, pressing apps, etc. It got either confused or refused to act upon my actions.

So, first we have to know how capacitive touchscreens work. To quote "Good Gear Guide":

Capacitive touchscreens work by sensing the conductive properties of an object, usually the skin on your fingertip. A capacitive screen on a mobile phone or smartphone usually has a glass face and doesn't rely on pressure.

That means that if you get a conductive substance, like water or sweat, in the way, it fails to detect your actions properly.

Borrowing an explanation from Embedded for capacitive devices that are neither water tolerant or waterproof, like my cellphone (and I guess yours too):

Fingers [and Water] are conductive, so they interact with the electric field that is set up around the touch sensors. [Water drops can produce] the same signal level as a finger for a touch sensor that lacks any features for water tolerance, even when no finger is present. (See the image below.)

Example of a finger touch and drops of water.

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i think that perhaps more than the sweat itself, the phone is reacting to the humidity of your hand

the touchscreen device have problems with performing in high humidity, also collect condensation inside when going from an air-cooled environment to the hot & humid outer world

they make special gloves for runners to wear (year-round, so yes! they have a summer version)

the gloves wick away the perspiration & have Touch screen compatibility

Good luck to you :)

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protected by Community Aug 12 '18 at 6:26

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