X-ray affects voltage reference accuracy ? - Page 1
Forum section: electronics / projects

author: BravoV
author_rank: Super Contributor
timestamp: December 03, 2011, 01:26:48 pm
content: Recently read an interesting article at Intersil, download it here :X-Ray Effects on Intersil FGA References ---->http://www.intersil.com/data/an/an1533.pdfCurious if this is an issue for high precision measurement tools, or its nothing to concern about, especially for those engineers that do lot of flying while carrying their measurement tools along with them ?

author: ejeffrey
author_rank: Super Contributor
timestamp: December 03, 2011, 05:27:05 pm
content: This only applies to a specific type of voltage reference: floating gate references, which are basically a flash memory cell with an exactly calibrated gate charge. X-rays can cause ionization that lets a bit of charge leak out of the stored gate. The application note is basically a guideline for manufacturers to make sure your equipment doesn't get screwed up going through airport security

author: wkb
author_rank: Super Contributor
timestamp: December 03, 2011, 05:33:44 pm
content: X-rays strong enough to cause ionisation would be really unhealthy, so not suitable for passenger security screening.That said, floating-gate electronics (like e.g. the old UV-EPROMs) can be made to leak their charge by feeding them enoughenergy, like by short-wave UV radiation or X-rays.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 03, 2011, 08:26:42 pm
content: The only x-rays they found to be potentially problematic are those used in checked baggage screening. Depending on the scanner used and how long it stays in the machine, it is possible the references need shielding. These scanners use far higher doses than those used in carry-on luggage scanners or the backscatter imaging systems used for passenger screening.

author: wkb
author_rank: Super Contributor
timestamp: December 05, 2011, 08:29:00 pm
content: Quote from: ejeffrey on December 03, 2011, 08:26:42 pmExactly. This is the same reason your film (yes, I still use film, rollfilm evenin checked luggage is typically a write-off if gets X-rayed. Mind you, still not all checked luggage is, although the % X-rayed rises all the time.

author: Psi
author_rank: Super Contributor
timestamp: December 05, 2011, 11:59:21 pm
content: I work on airport xray machines sometimes. (The carry on baggage kind)Due to the number of people complaining that data on their camera or laptop had been damaged by the machine (which is absurdly unlikely due to the level of xrays) we set out to write a report and do some physical tests ourselves.We got a few different things, usb key, different memory stick, hard drive, floppy disk etc.Then positioned them in the middle of the xray beam (which is around 5mm wide) switched off the conveyer belt and left them their for 3minutes continuous exposure.Afterwards we tested all the devices and confirmed every bit of data was bit for bit correct.Given the time a object moving through stays in the beam, speed and beam width, the area exposed to x-rays during the test was calculated to have received a similar dosage to being put through an x-ray machine over 9000 times.We concluded that the most likely explanation for peoples thinking the xray machine had damaged their property was corrupted file systems / fat tables. Since that can occur from unplugging without unmounting or using dodgy photo kiosks. It also doesn't show up when it occurs, photos just start overwriting older ones.Which isn't obvious until the end of peoples holiday when they get home and try to copy off all their photos.Naturally they think the last thing they did caused the problem.

author: wkb
author_rank: Super Contributor
timestamp: December 06, 2011, 09:21:47 am
content: Carry-on luggage X-ray machines are typically not a problem for film up to 1600ASA. I tried 3200ASA (eh, ISO3200 they call thatthese daysand I could not see any ill effect. Repeated exposure, given that X-ray damage to film is cumulative, would at some point become a problem. And obviously color film is trickier than my ISO3200 B&WPresumably older equipment can be nastier, also take care if you are in the habit of travelling to places like Pyongyang