Cell Phone Touchscreen Doesn’t Work

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Cell Phone Touchscreen Doesn’t Work

Post by rogerwimmer » Mon Feb 06, 2012 11:59 am

Doc: I hope you aren’t tired of answering questions about cell phones because I have another one. For Christmas, I received a smartphone that has a touchscreen. I have never had one before and it worked great until yesterday. I wonder if you know why.

Here is the problem: I can scroll horizontally and vertically with my index finger, but when I try to zoom in or out with my thumb and index finger (opening or closing motion), nothing happens. However, that only happens with my right hand. It works fine with my left hand. Is there something wrong with my hand, or what? I didn’t drop the phone on the floor or ground and also didn’t drop it into water. Should I take the phone back to the store? Please help. - Steve


Steve: As we agreed, I would provide an explanation for the readers so they know what we did to answer your question.

To all readers: Fortunately, Steve included his email address in his original question and I was able to write to him to ask a few questions.

Email 1: In my first email, I told Steve that the best thing for him to do was cut off his thumb and just use his index and middle fingers on his right hand, but he didn’t think that was a good idea. I also asked him if he was sure that he wasn't accidentally given a left-handed cell phone, but he figured out that I was teasing.

But I also I asked him if there was anything different with his thumb from when he was able to zoom in an out. I said, “The problem is not with your phone because the zoom function works with your index finger and thumb on your left hand. You had to do something to the thumb on your right hand.”

Steve wrote back and said nothing was different with his thumb. Hmm.

Email 2: I wrote back and said, “I don’t believe you. You had to do something. Think about it. Better yet, look at your thumb. What’s new or different?” He wrote back and said, “No, really. I swear there is nothing different.”

Email 3: I said, "Steve, don’t make me come out there. No, wait, don’t make me send my buddy Guido out there because he WILL do something to your thumb that will, how can I say this, not be pretty. Look at your thumb! There is something different now than when it worked for scrolling on your phone.”

Steve answered, “Wait! You are correct! I cut my thumb yesterday when I was working on my car. I now have a bandage on my thumb. Sorry about that. I forgot about the bandage.”

Before I get to email #4, can you figure out why Steve couldn’t zoom in or out on his phone with his right hand?

Waiting....Aliens? Bad Karma? Too much shellfish? OK, enough waiting.

Email 4: I wrote back and said this:

"Steve: You forgot about the bandage? Well, OK, then. On to your answer . . .

Most cell phones that have touchscreens use a technology called capacitive sensing that uses a person’s body as a conductor. The bandage on your thumb is not a conductor and, therefore, is “blocking” your body’s conductivity. In other words, as long as you have the bandage on your thumb (or a cloth, glove, or other non-conductive material), you will not be able to use it to scroll or zoom on your phone. If you don’t believe me, take off the bandage and zoom away."

Steve wrote back and said, “I took off the bandage and guess what? IT WORKS! I CAN’T BELIEVE IT! Thanks a lot.”

End of story, but if you want more information about capacitive sensing, click here.


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Roger Wimmer is owner of Wimmer Research and senior author of Mass Media Research: An Introduction, 10th Edition.

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