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The first step of calibration is to head out into colder climes and enter a verified temperature.
There's no shortage of weather apps that'll give you local temperature and forecast information, but let's face it: they're not exactly infallible. Wouldn't it be neat if you could just whip out your iPhone, and not have to hunt down an actual old-fashioned thermometer?
It turns out you can, at least in theory. No current iOS device boasts temperature sensors, but Thermometer 147 claims to measure ambient air temperature using only the onboard audio hardware. Because sound waves travel faster in warmer air, one need only measure the time it takes a sound to get from speaker to microphone.
Once you've calibrated, you're ready to hit the button inexplicably marked "0.05" for a temperature reading.
Sounds simple enough, right? There's a substantial wrinkle, though: because sound waves propagate through air at hundreds of miles an hour, and the distance between speaker and microphone is trivial, the time delay must be measured in microseconds. That's millionths of a second. Can a humble iPhone app accurately measure such infinitesimal delays and deliver the 3.6-degree precision it promises?
Apparently not. We dutifully measured and entered temperatures both cold and warm for calibration purposes, despite the odd requirement that we quit out of the application between every measurement. No matter how many times we calibrated, Thermometer 147's stark text-only output could've been mistaken for a random number generator. A verified 72-degree Fahrenheit room would register in the low forties one moment and the high sixties seconds later. With that kind of uncorrectable variation, you might as well just lick a finger, raise it to the wind, and speak the first number that enters your mind.
There's no menu, so you'll have to leave and return to the app every time you want a new reading.
The bottom line. We were initially intrigued by the possibility that this really would work -- plus, when we downloaded it it was free. Well, it turns out it doesn't work, and the price has been raised to $9.99. That makes this one easy: Thermometer 147 is of no practical utility whatsoever in its current form.
iPhone or iPod touch running iOS 3.0 or later. A desire to waste $10.
An interesting experiment in physics.
Temperature readings are rarely the least bit accurate. Interface is minimal to the point of non-existence. Requires endless restarts. Price went from free to $9.99 even though it still doesn't work and is exceedingly ugly.