So, have I got this radiation calculation correct?(and another related question) - Page 1
Forum section: electronics / general

author: XOIIO
author_rank: Super Contributor
timestamp: February 06, 2016, 02:45:19 am
content: So, I finally got something radioactive, an old bullfinch mantle, complete with thorium and asbestos string.Now, assuming my Geiger counter is reasonably accurate (last calibrated in 84 I believe, yes it is a bit out of date), this puts of at most around 4 milliroentgen per hour peak (when the meter is right against the thickest quantity of the mantle).So, that converts to 34.78 microsieverts, and according to the xkcd chart, a flight from NY to LA is 40 microsieverts, so in effect, holding the mantle in my hand for 1 hour would expose said hand to just under the amount of radiation my whole body would experience in one flight.Also, based on that, I think that I would need to hold the mantle in my hand for 1,437 hours to reach the safe annual radiation dosage for radiation workers, or 966 hours for civilians (at least in that hand)Just wondering if someone can confirm I have got that all straight, or perhaps I made a mistake somewhere.http://xkcd.com/radiation/http://www.convert-me.com/en/convert/radiation/I also want to make something with an arduino that can hook up to the headphone connector and count the clicks to calculate and give this information automatically, but I think that it might not work so well, or at least it would be a bit off, since it clicks quite rapidly when the radiation gets decently strong, I'm not sure if they might overlap to much to cause an issue. The "clicks" seem to max out about half a volt, and I'm curious what would be the best way to pick up those signals safely, without risk of 5v from the arduino being piped into geiger counter. Never dealt with opto-isolators before but that seems like a good start, I could also use pointers on how you go about turning a signal like that into an input, I'm not sure if it would be as simple as setting it up similar to a button. It's 5v dc so it wouldn't need an analog to digital converter I don't think, it does just make a piezo speaker click.Pictures to make it a bit more interesting:

author: Someone
author_rank: Super Contributor
timestamp: February 06, 2016, 12:08:42 pm
content: Quote from: XOIIO on February 06, 2016, 02:45:19 amShort answer is no, you dont have it rightThe long answer is twofold, the radiation follows the inverse square rule so will decay quickly away from the localised source, and the weighting functions for the body parts vary wildly. It can be hard to get good information and the wikipedia article is lackinghttps://en.wikipedia.org/wiki/Effective_dose_(radiation) but the basic result is that a health physicist would allow huge localised absorbed doses to the hands compared to the whole body dose (or equivalent thereof). Its an area of ongoing research and there is a lot of training/learning on the road to become a competent health physicist:https://en.wikipedia.org/wiki/Health_physicshttps://en.wikipedia.org/wiki/Certified_Health_Physicist

author: XOIIO
author_rank: Super Contributor
timestamp: February 06, 2016, 01:36:19 pm
content: Quote from: Someone on February 06, 2016, 12:08:42 pmYeah, the whole radiation amount to dose isn't a super simple thing lol, plus depending on the radiation type it could just be stopped by the skin, I just wanted to know if I had it right in theory. I doubt holding it for 966 hours would give my hand 1000uSv of radiation unless I had a regulated source of gamma radiation (which considering I am not bruce banner, I do not have)The mantle is only putting off beta radiation, no gamma, and sadly I don't have one of the much rarer alpha radiation detecting 700's so who knows lol. It is thorium though so you can make an educated guess.

author: Stonent
author_rank: Super Contributor
timestamp: February 08, 2016, 07:55:24 am
content: Geiger counters can only be used to measure counts for anything other than what they are calibrated for. If your cdv700 has radium then you can accurately measure radium. If it has depleted uranium then that's what you can measure.Most modern counters are calibrated to Cs137.One click of Plutonium has a lot different energy than one click of Potassium 40. So the roentgens and sieverts scale has to be different.

author: Stonent
author_rank: Super Contributor
timestamp: February 08, 2016, 08:08:28 am
content: Also these cdv700 units pulse at -18V so you need to factor that in since it is not suitable for an arduino. A 2k resistor should suffice I think for the input to an optocoupler at 18v. Please someone correct me if wrong.