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Every time I'm near a Genius Bar I see a lot of ENT (ear, nose, throat) microscopes peering down the headphone jack of various iPhones. I asked about it and found that the moisture sensor is down there, and if your device got wet then it turns red, and the purpose of that is that you don't have a warranty and don't get a free new device if it has mysteriously died but the cause is moisture.

I'm curious about how these things work and whether this simple examination could be subverted. I don't have a wet iPhone and I'm not looking to defraud Apple here, but I'm curious.

  • The sensor must involve a chemical reaction, if it didn't show the indicator color when it dried it wouldn't be much good. What is the reaction and is it reversible? Would the required reagent be safe to drip down the headphone opening?
  • Could one buy a new sensor component, open the phone and replace it?
  • How about simply getting a material that looks like the sensor, opening the phone and putting it in place of the sensor - an inert sensor?
  • Simplest of all, painting the sensor - if the "OK" color is white then a paint marker should do.

Again, not trying to get a free phone here. I'm curious about devices like this since I saw my first "tip-n-tell" on a shipping carton, and played with Maxim iButton temperature loggers.

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While these questions are interesting, I'm not sure they're very well suited for Ask Different... – jtbandes Mar 22 '12 at 22:28
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The FAQ says nothing against it. I think it's a legitimate question for AskDifferent. – Andrew Larsson Mar 22 '12 at 22:33
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You say you don't want to defraud Apple, but all your questions aim to do just that. You ask of ways to reverse the chemical reaction, replace the sensor entirely with one that hasn't "gone off," a chameleon sensor, or to mask the color. None of those questions have any serious scientific merit or aid the community at large. They only serve to do exactly what you claim you have no interest in doing. – cksum Mar 22 '12 at 22:44
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Well how far does this go - do you think pentalobe drivers (or for that matter tri-wing or torx) should be outlawed? Knowledge is interesting for its own sake. In contrast with the thermochron button and the tip-n-tell sensor these do seem like fallible devices. If I'm really a criminal and want free iPhones, simply stealing them is surely a better way. Don't do that either, readers. – Adam Eberbach Mar 22 '12 at 22:46
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Every cellphone and most laptops contain them, and have long before the iPhone came out. This is not an Apple specific query, and I disagree that it's suitable for this site. – Adam Davis Mar 22 '12 at 23:01
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closed as off topic by gentmatt, Graeme Hutchison, Matt Love, jtbandes, Ian C.♦ Mar 27 '12 at 21:30

Questions on Ask Different are expected to relate to Apple hardware or software within the scope defined in the FAQ. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about closed questions here.

1 Answer

up vote 5 down vote accepted

An inert "sensor" would be white paper. An actually working sensor could be paper coated with cobalt(II) chloride, whose hexa hydrate (cobalt chloride "containing" water) turns light red. If you want to tamper with the original sensor, think of water free clear coat.

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Thank you. I know next to nothing about the chemistry of these sensors and this is interesting to me. I hope nobody assumes you're interested in facilitating fraud by telling me this. – Adam Eberbach Mar 22 '12 at 22:49
@AdamEberbach Actually, I don't know what kind of water sensor Apple uses. But this reaction changes from light blue to light red. This could be what they are using. And it's one of the most common test reaction for water. – Max Ried Mar 22 '12 at 22:52
Why does this answer get downvoted? – Max Ried Mar 22 '12 at 22:58
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For the same reason that people are downvoting the question...you're being judged as guilty by association. It's unfortunate. – AJ. Mar 22 '12 at 23:00
This is white hat hacking. – Max Ried Mar 22 '12 at 23:01
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