Ok, what the heck OP, geiger counters?  who needs that?  and arent they expensive??  read on -

well - yes, you, and surprisingly, No.

yeah - chernobyl on HBO got to me, but I had a high-range meter (CDV 715) for a long time and always wanted and low-to-mid range meter, and finally found one.  in fact its so awesome I am posting about it, because it really is that good.  Also both my cdv 742 dosimiters crapped out and honestly I dont know if they were ever that reliable.

Possible threats;

Nuclear war : you'll want a high range meter too, but everything will get low-range but still deadly soon after and you will need a low range meter for that.  I personally live within fallout range of 10 military facilties, and nowhere near the blast radius of any.

Nuclear accidents: I live within fallout range of no less than 8 nuclear plants.  any one of which could dump on me depending on which way the wind is blowing

Terrorist / dirty bomb: could happen anywhere at any time

Radioactive stuff in your AO : want to know if you live on a rich uranium deposit and are going to have an increased chance of cancer?

for all these needs and more, a good radiation meter could be super useful.

but the devil is in the details;

you can get a high range meter like the CDV 715 (and I did) which uses an ionization chamber, but has a lower limit of detection of about .1 Roentgen (1 millisievert).  too high to be of practical use for low level fallout, and only useful in a nuclear exchange. - basically the "am i fucked or not fucked" detector.



OR

You can get a low-range meter which has a geiger-muller tube but the limit is how much radiation they can detect hits a wall when the tube is saturated by too much radiation, so they usually only go as high as 4 millisieverts (.4 Roentgen)  This is too low when the fallout is fresh.



recently however some new instruments are available which are more mid-range and have pretty reasonable cost too.



This model has 2 geiger tubes using independent power supplies - one sensitive low range tube, one less sensitive high range tube.  this lets it go as low as actually zero and as high as 4.2 Roentgen (42 Millisieverts) and everything in between.  This also deepens the overlap between this meter and a high range meter such as the CDV 715, giving confidence at the extreme ends of both meter's sprectrums.

cost new - today, $125.   Amazon

These new tech meters also function to track history and act as a dosimeter as well, which means even though the maximum reading is 4.2 Roentgen, the meter can act as a dosimeter up to a much higher number than that.  for example if you spent 10 hours at 3.5 Roentgen, then the dosimeter function would read 35 Roentgen.  This is good because after you come out of your fallout shelter readings will be in the .1 to 5 Roentgen range and this will be the exact time you need a dosimeter to track your exposure, and the exact time that the extra high range of that meter will pay off.  This is the EXTREME low end of a high range meter like the CV 715 meaning your readings are real iffy and also on a CDV 742 dosimeter reading your exposure on a scale of 1-200 is going to be a shit show also.  The GMC 500+ is cheap enough to use as a personal dosimeter and have several.

But how accurate are these things;

I took it on a commercial flight for confirmation.

Here is my data plotted in Excel downloaded from the GMC 500+ - there are other similar plots from other folks on the internet which inspired me to take it along but this is 100% my original data.  I compressed out some of the time because otherwise the interesting data is small and the white space was big.



a few interesting things -

1: the background level in the US varies from .05 to .2 microsieverts (uSv) - at the airport in ATL before the first flight you can see the background level is higher (around .2 uSv) than after landing in PHL (closer to .1 uSv).  You can just see it tick back UP after getting back to ATL.  At my home it is hovering around .12 uSv, which makes sense since I am north and just outside the known uranium rich areas south of me - also why my radon is lower too.

2: The Xray machine spiked so hard I had to clip it - it reads 245 microsievers/hr

3: The flight out was pretty normal, but on the return storms caused us to fly at a lower altitude.

4: Readings on the plane confirm the device's function and accuracy.. and also just how much the atmosphere protects us from Cosmic rays!

5: I lost the x ray machine in ATL due to accidentally clearing the history through the UI, but did take a picture of it first.  my calculation based on that was a peak of 670 microsieverts/hr but only for 3 seconds - it had a much higher spike than in PHL (2nd trip) - which was 245 microsieverts.  I assume different hardware, as others have reported similar findings.

Government sources identify radiation levels in an aircraft as up to .003 millisieverts (3 microsieverts) which is great confirmation of my readings which peaked at 2.5 microsieverts, but on a short flight like this I doubt we go as high as long-haul flights which sometimes go up to 38000 ft.

So there you have it, an excellent tool, which due to the high range tube is also powerful enough to use in a real nuclear emergency and priced low enough to own today.

Here is a chart I made to convert between Roentgen, Milli Roentgen, Sieverts, Milli Sieverts, Micro Sieverts and CPM (count per minute) so I could quickly lookup any reading from either a high range or low range device and see at a glance whether safe to be there and if so for how long

I found that converting from sieverts to roentgen and back and milli and micro - there is a pretty good chance of being off by a factor of 10 so I repeated the whole chart in both so there is no multiplying, just take a reading and follow across left and right.

Wow.  You clearly spent a lot of time on this.  Nice job!

Great write up  Bionicmonkey.

I spent 20+ years in Rad Protection with instrumentation being a specialty.

The above post is one of the best I have seen on this subject.  Many post type things on this subject quickly go way out of bounds as to any useful information. As in they have a surplus dosimeter that with time go off scale and they start worrying about high dose rates. Ion Chamber dosimeters (leak - electrical charge) over time and as they leak their indicator goes up scale. Given time they will go off scale.

Just a note - The pancake probe pictured - yes is a very sensitive probe.

It is also a very fragile probe. Touch the thin probe face with just about anything and it will pop.

These probes use to cost around $100 not sure what they are now.  At the time they were called an HP-210 probes.

Nice, I’ve been looking for a counter with a USB port for experiments and just general playing around.

My buddy explained the fragility of his pancake probe to his wife and cautioned her not to touch it. She immediately touched it

If you’re bored at the airport, set your phone to record a video before it goes through the x Ray. Mostly static and sparkly colors.

So that was the meter riding the basket through TSA? Did they pay you any special attention? I would have figured that would flip their "Off normal" switch. Our hospital uses very similar dosimeter/meters for most lab applications although they do own some surplus looking Geigers as well.

The GMC 500+ pictured above has a USB, and you dont need to capture video because you can download it later.  It's not a pancake probe, it has tubes.  If you get the GMC 600+ it has the pancake type tube but while being super sensitive to low levels of radiation, it also reduces by 10x its top end, so it can only read up to .4 Roentgen, which I feel is too low for fallout use.

it was in my bag.  the bag itself offers no radiation protection so I just put it in a front zipper pocket.  no grief from the TSA on either end.

I find it ironic the label on there is

"OCD ITEM NO"

office of Civil Defence.  

one other thing;

This is the GMC map http://www.gmcmap.com/index.asp

on it you can see readings from folks all around who have plugged into the usb port and let her rip.

SO here is the scenario;  you hear the news that blah blah nuclear plant blew up - you need actionable intel on where the radiation is, how high and whether to shelter or evac, and if the latter, which way to go.  panic and misinformation will rule the day, but electricity and the internet may well still work.  in this case you now have a resource which you can check radiation readings across the country or narrowly in your AO and around which will give you data in real time.  your meter will tell you what is going on in your area, this will tell you where it is safe and let you see the trends of how it is going

Imagine if such a thing existed during chernobyl?  while the politicians were denying and folks were getting irradiated.

Excellent post.

What I want to know, is WTH is going on outside Bloomington??

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I have a few things, and my neighbor is a nuclear engineer, so I imagine he has a few things also.

Never had a blip with TSA.

if you click the pin it will tell you the date of the latest data - likely not fresh.

ive got some uranium ore which is super low grade but will definately make a blip.  some folks have cesium and all kinds of things.

Obviously it will vary on countless factors but I would get whatever would be best for measuring fallout from the weapons. Need to know when it’s safe to go outside and for how long. So I’m guessing option one.

As inexpensive kits go, these are pretty nifty - Nicely designed, and well-documented.



The display has the option of displaying in counts per minute or uSv/hr, and also can display accumulated dose over two user-programmable time periods.

They can be set to apply a correction factor for the specific type of GM tube you're using, and can switch between two different tubes (applying the appropriate correction factor to each) - very handy for pairing a low-range tube with a high-range one in the same unit.

They're Arduino-based (with published firmware), so it's possible to add or modify features yourself.



He also has several other variants.

Not certain if this is the exact one, I know my wife paid about $500 for it.. but this what we have...

https://www.minerox.com/product-p/go768.htm

She wanted to test the tuna after Fukushima...

I have this one:

GQ GMC300EPlus Fulfill Digital Nuclear Radiation Detector Monitor Meter

I got it before I went in for my Radioactive Iodine treatment for my cancer.

I wanted to get a background reading and be able to have some confidence I wasn't highly radioactive after three days of quarantine.  I came home after the treatment and we could hear the thing squalling on the kitchen counter from outside front door.  It was maxed out.  Interesting how much radioactivity you pee out and how short the half life seems to be.  I stayed away from everybody for a week.

Good thread OP.   I’m tempted to get one, but I’m not sure I really want to know.    It’s not as if I can just up and quit work at this point.

Ludlum Measurements makes a very nice little "Personal Radiation Monitor" that covers a ridiculously wide range of radiation levels - The Model 25.



It's tiny - uses just a pair of CR2032 lithium coin cells. Claimed battery life is 6,000 hours.

At around $620, it's definitely not an entry-level meter - But it's made in America by the "Cadillac" of geiger counter manufacturers, and comes with real customer support.

Thanks all for the kind feedback.

Regarding the GMC 300+ (a great meter, btw) and the inspector X (not aware of it, but probably also good) and the kit boards... which are all pretty darn good, but also dont have the 1 feature I like on the GMC 500+  - the mid-high range tube..  so not to bash them, because they are good meters, but I do want to emphasize why the mid-high range geiger meter may make a difference in your preps;

let me start by explaining my understanding of doses and rates; and the "am i fucked" question.

I am going to do this in roentgen because roentgen make the most sense at this scale - 1 sievert = 100 roentgen, 1 millisievert = .1 Roentgen.

DOSE: accumulation, but for this purpose lets confine to short term accumulation, not lifetime, as the body heals a certain rate indefinitely.  we'll leave out thyroid cancer as well since a: there is no rate/correlation evidence and b: we'll assume you have potassium iodine on hand.

10 Roentgen : max known dose with literally no effect
15 Roentgen : temporary sterility in 1% of sample group within 3-9 weeks
50 roentgen : reduction in bone marrow production, long term eye damage
100 Roentgen : nausea, vomiting, flu like symptoms
200 Roentgen : limit for expected survival without medical care
250 Roentgen : permanent sterility in females, chance of death due to complications
350 Roentgen : permanent sterility in males,
400 Roentgen : limit of expected survivability with advanced medical car
400+  : expect to die, maybe not so lucky if you dont.

ok, now lets take a look at the scale on the CDV 715 included with every 1950's nuke shelter.  
x .1   .1  to .5 Roentgen
X  1   1 to 5 Roentgen
X 10    10 to 50 Roentgen
x100   100 to 500 Roentgen

.1 R / hr = 1 R in 10 hours - that is a lot, and not somewhere you should be long term - (thats 876 R / year!) - but you can move about and perhaps evac at that rate
below .1, perhaps .01 (below scale) - that's still 87 R / year, but the urgency is simply not the same as on-scale

why doenst it read over 500, well, because at 500 R / hr if it goes off-scale, you are basically fucked and its almost irrelevant how fucked.  oh geez, look how fucked I am..

so this is perfectly balanced for a nuclear fallout when the end result is being evacuated by the gov.

But - what if :
A: you dont have a cdv 715
B: there is no cold zone to get to
C: the govt isnt coming and you have to self rescue
D: The issue you are facing is lower grade than that

in those cases you DO need to know a reading that is ;

Above background level
AND
Below "im immediately fucked" levels.

*eta: more like "i'm fucked long term if i stay here"

but to do this, it has to be able to get imho at least to 1 R.  The GMC 500+ is unique in its ability to get to 4.2 R without a ion chamber like the high range only meters.

why does that matter

lets look back now at dose rates;

at .001 R / hr that's 8.7 R/yr  - not ideal, but only slightly over the OSHA limit, and less than astronauts receive
at .01 R / hr that's 87.6 R /year.  super bad - would NOT like to live there.  but you could survive that if you had no other choice.
at .1 R / hr that's 876 R/ year.  you will hit 200 R in 80 days, and that wouldnt be recommended
at 1 R / hr you will hit 200R in about 8 days.  this would be a FAST evac / shelter in place rate.  
at 5 R / hr you would hit 200R in less than 40 hours, this is not a place you want to be AT ALL.

now - if I was standing at the threshold of my bunker 2 weeks after the event, holding my meter on a stick out the door, i'd want to know which of the above I'm dealing with. - and the Tipping point is 1 R - above 1 R its too hot.  below, I can make an informed decision on whether being out of the shelter is worth it.  if the meter is saturated and reads either at scale, zero, or "saturated" then I wont know which it is and that makes the meter worthless in that circumstance.

eta: point being - all the useful information is in the .001 to 5 range.  under that will be helpful LONG TERM, but above that is only of limited value - this is the sweet spot.

what is the expected rate from fallout - it will vary, depending on how hot your AO is, but it will follow the 7/10 rule

the radiation will dissipate 10x every 7x interval



48 hours to 10 R/hr
2 weeks to 1R/hr
14 weeks to get to .1 R/hr
98 weeks (2 years) to get to .01R/hr    not habitable
14 years to get to .001 R/hr - that's 9 R/ year, beyond OSHA limit
100 years to get to .0001 R/hr - that's 1 R /year, acceptable
700 years to get to .00001 R/hr -  (background radiation levels)

This is literally why the general advice for fallout is that you would shelter for to 2 weeks (which you could reasonably do without any kind of meter because of the above), because the decay happens and then at 1 R ish it may be reasonable to expose you to a few R to get out and get clear.  If you are on your own (no govt help), you may have to expose yourself to some R at this point and over the coming weeks to clear an area like they did around chernobyl, by moving the top soil and killing the animals and basically burying everything.

if your meter doesn't read as high as 1 R then you have a gap from that 2 week moment until however long it takes for your meter to be able to read in such a high field.  To me that is a problem, you should be aware of if you believe that fallout is a possibility.

or you know....  move away from all the danger?

Like Somalia?

In 1991, the government of Somalia collapsed. Its nine million people have been teetering on starvation ever since – and the ugliest forces in the Western world have seen this as a great opportunity to steal the country's food supply and dump our nuclear waste in their seas.

Yes: nuclear waste. As soon as the government was gone, mysterious European ships started appearing off the coast of Somalia, dumping vast barrels into the ocean. The coastal population began to sicken. At first they suffered strange rashes, nausea and malformed babies. Then, after the 2005 tsunami, hundreds of the dumped and leaking barrels washed up on shore. People began to suffer from radiation sickness, and more than 300 died.

Ahmedou Ould-Abdallah, the UN envoy to Somalia, tells me: "Somebody is dumping nuclear material here. There is also lead, and heavy metals such as cadmium and mercury – you name it." Much of it can be traced back to European hospitals and factories, who seem to be passing it on to the Italian mafia to "dispose" of cheaply. When I asked Mr Ould-Abdallah what European governments were doing about it, he said with a sigh: "Nothing. There has been no clean-up, no compensation, and no prevention."

https://www.independent.co.uk/voices/commentators/johann-hari/johann-hari-you-are-being-lied-to-about-pirates-1225817.html



exactly the use case in fact for a small, inexpensive low to medium range geiger meter, where perhaps an ion-chamber high range meter wouldnt detect what is an arguably dangerous level of radiation.

Wasn't this due to corrupt disposal via the mafia or something like that?

You convinced me to take on a small electronics project.  Just ordered a trio of CD meters to tinker with: CDV-715, -717, and -720.

"Welcome to arfcom, get out your wallet."

Awesome, congrats... :-)

CDV-718...must...resist...

@bionicmonkey you are the reason my wife says no more toys for a year!

...the V-718 will be here Thursday.

What the heck happened?  I thought I had been immunized to this behavior by the NVG section.  Sheesh.

Canbera UltraRadiac personal dosimeter
Used one for years at work on my belt daily
Have my own now. Rugged small accurate

https://www.thermofisher.com/us/en/home/industrial/radiation-detection-measurement/portable-radiation-detection.html

We have two, low range geiger counters in the house. I bought the first one, several years after Chernobyl to check food and everything else for radioactive contamination. It's a Russian made Bella meter. I checked it on a nuclear, conveyor belt scales at work and it did show the correct amount.

I had a heart stress test several years ago. They inject radioactive isotopes in blood to monitor blood flow. The isotope's half life should be at 6 hours. I got home from the stress test and decided to check if the meter would pick up anything. It showed zero counts and acted as if it were broken. I left it on my desk and went to get a new battery. Once I was far away from the meter, it started "singing" a continuous tone. I got closer to the meter and it stopped again. It was simply getting over-saturated by the radiation from my body. WTF? The doctor told me that it's harmless. He said I'd get radiation dose about equal to a chest x-ray or to radiation dose received during an hour flight at 30,000 ft. I think he was lying. Based on the readings, I was exposed to at least 4 RADS. This is quite a bit! The doctor's nurse, who was working with me, was about 7 months pregnant. I wonder how much exposure she gets from working with all that sh*t?

A new meter I bought, is made in the USA, Radalert50. Besides Gamma, it can also detect Betta and Alpha. It should also be more resistant to over-saturation at high levels but I have no way to check it now.
I probably need to get high range counter too but can[t decide what to get. A Soviet DP-5V counter will probably work well. This is what they used in Chernobyl. It was also used by the military. Any other suggestions?

Here is a pic of my Radalert50. We live 10 miles SW of Catawba Nuclear station. Most of the time, we are upwind from it though.

where did you get it? I searched for CD V-718 with no results.

I need another pocket pistol, before I buy a Geiger counter.

I really don't need a Geiger counter...maybe a Honda EU2000i, but not a Geiger counter.

Chris

Found a single used set for auction.

Care to share how much you paid for it? Is it a low or high range meter?

Effectively it is an AN/VDR-2 scaled in Röntgen instead of Gray, and cased in Civil Defense yellow instead of olive green.

0.001 mR/hr to 10,000 R/hr achieved with a pair of G-M tubes, autoscaling.  Beta/gamma probe.

$780.  Price definitely included a premium for being a fewer produced model.  I saw a VDR-2 for auction at the same time as the V-718 with the latter asking about $150-200 more.

The radiacmeter for the V-718/VDR-2 utilizes only the one beta/gamma probe.  There is a more capable system that comes in the same olive green casing, the AN/PDR-77, and it accepts multiple different probes and has deeper processing. That unit runs about $1,700 used that I've seen.  I believe the '"V-718A" is the civil equivalent to the PDR-77.

One of the down sides to old "analog" geiger counters is that they require occasional recalibration.

The integrator circuitry that converts pulses produced by a GM tube to the moving needle on a meter movement is inherently prone to drift - The values of its components gradually change over time, temperature, humidity exposure, etc.

Typically, each range on the meter uses its own set of components, each with its own drift.

Recalibration involves exposing the meter to known amounts of radiation (or feeding the meter electrical pulses that simulate what the output of a GM tube would be when exposed to that radiation), and then adjusting the meter so that it displays the proper radiation level once again. This is repeated for each range on the meter.

And this needs to be done every several years.

Digital meters are better in this regard, because they simply count pulses from the GM tube, and show the count directly on a LED or LCD display - No analog integrator circuitry required, and thus no component drift that requires recalibration.

Thanks. I appreciate your reply. I'll probably just get the Soviet military Geiger counter from a Ukrainian seller on Ebay (link was posted in one my previous posts). Currently, I just can't justify spending $1,000 for a meter that will probably never be used.

Just for clarification of the prices, because I write weird.

VDR-2 ~$550
V-718 $780
PDR-77 ~$1,700

So you seem to like the GMC 500+.  Fast question then...is it able to only download data to a PC, or is it able to communicate with an IOS/MAC format laptop or smartphone?

Arrival.

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Now waiting on the trio of high range meters to tinker with and a couple other things.

ETA: I've got some nice clouds drifting by on a breeze right now.  As the clouds occasionally block the Sun the background reading drops about 10uR/hr. That's just cool to watch, and shows how good water is at attenuation, even as simple clouds.

i do - at the cost its a slam dunk esp compared to the $600+ options which is whar it cost to do better.

the interface for download is serial over usb and all the software lools to be windows oriented.  that leaves you making your own app or running windows in parallels on your mac

I'm pretty uninformed when it comes to dosimeters, but aren't they reliant on how well they're calibrated?

ETA: From reading this thread, seems like modern, digital, varieties escape this pitfall.

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Ambient: 15µR ?
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Test card:  32µR ?
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Test card: 2,080µR ? + ß
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Great post.  I went through the hazmat tech course in Nevada a few years ago. Free if the local .gov / FD/ PD will send you. Currently doing background readings around the county to gather a baseline. Part of my job for the county. I thankfully have access to the equipment which is calibrated by the state.

An example of radiation in our common environment.

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Only 10x background radiation.  It doesn't get sporty until you add some zeros but sure enough, there it is, potassium-40.

Also naturally occurring in bananas!

Picked up some dinnerware...

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Was the plate made of uranium glass? Where did you get it? It doesn't look like one. Was it Gamma radiation only?

That is mostly beta.

Here is gamma only, ~4x background.
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The plates are glazed with Uranium oxide.  You are seeing reflected light instead of filtered, hence orange instead of green.  I bought the plates at a secondhand store.  I'm thinking of parting with the two smaller plates to help fund this little treasure hunt.