Post-mortem: MRI disables every iOS device in facility

Re:Post-mortem: MRI disables every iOS device in facility by kiesel on Tuesday October 30, 2018 @07:47AM (#18335607)

So, what could it be that makes iPhones "react" with helium? Helium is an inert gas and shouldn't really chemically react with anything in there.

Any clues why such an environment doesn't make Android phones behave in such a way?

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by chopin on Tuesday October 30, 2018 @07:56AM (#18335662)

The same thread explains it here: https://old.reddit.com/r/sysadmin/comments/9si6r9/postmortem.... Sounds plausible to me.

If it wasn't dangerous one could try the same with hydrogen. If the post is correct it should have a similar effect (if the device doesn't explode during the test).

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by hatsunearu on Tuesday October 30, 2018 @10:41AM (#18336891)

Basically electronic oscillators rely on a very small piece of quartz crystal that is cut in just the right shape. Quartz has a phenomena called piezoelectricity, where if you apply an electric field, it deflects slightly. Conversely, if you deflect it, it creates a small electric potential. A properly shaped quartz, when exposed to some circuitry (oscillator circuitry; positive feedback), it will resonant at its natural frequency, not unlike how a tuning fork resonates at its natural frequency.

Since the crystal is literally vibrating inside the metal can it's packaged in, the atmosphere around the crystal influences the natural frequency. Helium will make it vibrate it faster, since it presents less air resistance to the crystal.

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by alxlaz on Wednesday October 31, 2018 @11:47AM (#18346700)

Note, however, that MEMS oscillators (which modern iPhones use) and quartz oscillators are not the same thing. SiTime's MEMS oscillator is made of silicon, not quartz.

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by berbec on Wednesday October 31, 2018 @01:22PM (#18347580)

Would an iPhone lock up in a vacuum?

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by tyingq on Wednesday October 31, 2018 @11:45AM (#18346675)

"Any clues why such an environment doesn't make Android phones behave in such a way?"

A bit of googling seems to indicate most smart phones have a crystal oscillator. But, Android would have the advantage of manufacturer diversity...so lots of different types of crystal oscillators, perhaps some that are sealed better than the iphone ones, or quartz vs silicon, etc.

This does sort of illustrate an issue with the iphone tech monoculture. Lots of devices with similar components, and similar versions of software. Find something that adversely affects them, and you can disrupt a lot of people. It's probably hard to find something similar for Android since the hardware and even software varies a lot.

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by alxlaz on Wednesday October 31, 2018 @11:49AM (#18346731)

Most crystals have better sealing :-). SiTime explicitly(-ish) acknowledges that their older-generation packaging was less efficient on their website:

"How effective is the hermetic seal of MEMS oscillators??

One of the key elements enabling extremely stable MEMS resonators is SiTime’s EpiSeal™ process which hermetically seals the resonators during wafer processing, eliminating any need for hermetically sealed ceramic packaging. SiTime’s EpiSeal resonator is impervious to the highest concentration elements in the atmosphere, nitrogen and oxygen, and therefore acts as a perfect seal. Previous generations of EpiSeal resonators may have been impacted by large concentrations of small-molecule gas. Newer EpiSeal resonators are impervious to all small-molecule gases. Please contact SiTime in case you are planning to use a SiTime device in large concentrations of small-molecule gas, so that we can recommend an appropriate, immune part."

https://www.sitime.com/support/faqs

[ Parent | on HN ]

Re:Post-mortem: MRI disables every iOS device in facility by NormM on Thursday November 01, 2018 @08:04PM (#18359618)

Apple uses these oscillators. They are substantially more expensive than crystal oscillators, but are much smaller and use less power. This may explain why the Android phones, which are more price sensitive, didn't use them. It does seem that the current generation of SiTime oscillators don't have a problem with Helium, so perhaps current generation iPhones don't either.

[ Parent | on HN ]