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Ghost in touch screen laptop (Read 6129 times)

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#1 Ghost in touch screen laptop
July 28, 2013, 09:51:39 PM
Symptom: The laptop screen shows random selections that almost look like bubbles.

Suspect cause: The laptop touch screen angle has a sweet spot where the surface pressure generates phantom touch events/triggers.

Background: I was running some tests on my dad's Windows 8 Asus laptop going back and forth between his and one of my computers and noticed at one point that these gray expanding dots started appearing on his laptop screen.  At first I thought it was his screen saver but he didn't have one set up. Virus? Ran a check and found nothing. I should mention that I was operating the laptop with a bluetooth mouse so I was not physically touching the computer and hadn't touched it since it starting doing this. Task Manager turned up nothing suspicious but as I was operating the computer I noticed that the gray dots appeared to be selecting whatever they landed on which was really starting to piss me off; it would close dialogs, open programs, etc.. wacky stuff. 

I was pretty sure it was a virus but started thinking about what else would make selections.  He'd already had issues accidentally making selections with his thumbs with the keyboard touch pad and it dawned on me that it could be related to the touch screen. Having worked with touch screens, touch pads and LCD displays in the past, I remembered that they were pretty fussy about "flexing". For wall mounted keypads the touch pad gets twisted when you screw it down to the wall causing touch problems but for my dad's laptop I was thinking it might just be angle of the laptop screen and how the touch screen hardware was designed.

So how do I confirm my hypothesis? If I change the angle of the display and the problem goes away it certainly helps confirm my hypothesis but if it is a mechanical intermittent, I may never find the sweet spot again. What to do?  At the time I couldn't think of a better test so I just moved the display forward an inch or so and the problem went away, never to return.

I had to return my dad's laptop to him before I could reproduce the problem but it explained some other weird behavior he's experienced with the laptop; apps mysteriously closing,.. He really wasn't interested in the touch screen anyway so we're just disabling it on his computer.

This was such a weird and mysterious problem I thought there had to be others out there experiencing this ghost-in-the-machine behavior on their touch screen laptops (and probably other touch devices as well) so I wrote this post.  I hope it helps someone. 

Bob