Radiation and Geiger counter question

[mobile1]

I know very little about radiation.

I am a ham (amateur radio operator) that bought a Civil Defense Geiger counter at a hamfest (where people buy and sell stuff) to be ready for a leak at my local nuclear power plant.

In my home the Geiger counter reads 100 to 150 Roentgrens per hour, using the X-10 scale. But according to the information that I found, this would have already given me a lethal dose of radiation:

http://standeyo.com/News_Files/NBC/Roentgen.chart.html
http://www.nukalert.com/manual.htm

I must be doing something wrong. Can anyone please help to understand this?

Thank you for your help.

[HydroDave63]

Most of those radiation detectors were calibrated and worked just fine when they were sealed up in that box in 1964, I'm not seeing the problem here  

If you want to use that particular meter, or replace it with a calibrated meter, the good folks at http://www.ki4u.com/products1.php can help. It is a good website for the entry-level hobbyist, especially Bruce Beach's essay (there's your first lookup!)

[cedugger]

In my home the Geiger counter reads 100 to 150 Roentgrens per hour, using the X-10 scale.

Yep, a little off. We have some of these at work in our museum cabinets, and even had one calibrated to see how well it would work. Worked fine! If you actually want to use it, you'll need to get it calibrated. Background in your house should be less than 10 microRoentgen/hour (or 0.00001 Roentgen/hour). Your meter, even when working correctly, probably won't go near that low, so you should be seeing a reading at the absolute lowest that your meter reads.

Good luck with it, and have fun.

[mobile1]

My geiger counter seems to have lost its mind.  It's now reading much higher.  Either it's not working right, or a terrorist downstairs is building a dirty bomb.

Tomorrow I will take it for a walk outdoors to see if it drops.

I put a picture of it here:
   http://www.didah.com/misc/geiger.jpg

Question:  The meter now reads about 4.  On the X-100 range, does this mean 400 Roentgrens or 400 Roentgrens?

[HydroDave63]

My geiger counter seems to have lost its mind.  It's now reading much higher.  Either it's not working right,

Put on your ham thinking cap here.....it'd be just like you are getting rising pitch and audio on a radio with no antenna input...which part of the circuit is failing?

[mobile1]

I should add that when I switch the geiger counter switch to CIRCUIT CHECK it pegs the meter, rather than staying within the CIRCUIT CHECK range on the meter.  Is this normal?

[HydroDave63]

I should add that when I switch the geiger counter switch to CIRCUIT CHECK it pegs the meter, rather than staying within the CIRCUIT CHECK range on the meter.  Is this normal?

Dangit, had you mentioned this first....no, not normal, you've got an internal short circuit. Despite operating on two lovable D cells, your geiger-muller tube operates around 900V, so instead of a nice mellow swing of your 4-20 mA d'Arsonval movement from zero to battery status of "circuit check" you've got a bunch of energy coming back. Check the case for voltage to ground, the circuit board for any kind of debris or goopage, tin whiskers or possibly a short to the meter. I have an old surplus meter of another sort that has an external probe, and gave me a nice painful jolt of 900v from G-M tube to probe case. Like trying to hold a taser!

[mobile1]

I found the manual for this geiger counter.  Its troubleshooting chart says that its tube is bad.  So I am going to trash it.   

[HydroDave63]

I found the manual for this geiger counter.  Its troubleshooting chart says that its tube is bad.  So I am going to trash it.   

Trash the tube, or the whole meter?? Anyone with a Novice Ham license and a 30W Radio Shack soldering iron can swap out a G-M tube. I'm glad to see my Wiki-doctor diagnosis was correct 

[mobile1]

Too late.  I already disemboweled it for parts.

What should I buy now?

This Wikipedia article recommends the CDV-718, which can be had on eBay for about $35. 
    http://en.wikipedia.org/wiki/Civil_Defense_Geiger_counters

But how can I know whether it is calibrated?  Does it have a self-calibration procedure?

Or can anyone recommend a different type of unit for less than $50?

Thanks again.

[HydroDave63]

Too late.  I already disemboweled it for parts.

What should I buy now?

This Wikipedia article recommends the CDV-718, which can be had on eBay for about $35. 
    http://en.wikipedia.org/wiki/Civil_Defense_Geiger_counters

But how can I know whether it is calibrated?  Does it have a self-calibration procedure?

Or can anyone recommend a different type of unit for less than $50?

Thanks again.

It's like asking "what kind of rig can I buy for $100 and get moonbounce?" In both cases, if the incoming signal (i.e. radiation) is strong enough,it is possible to have a workable result, but would be very insensitive and not fulfilling.

No self-calibration procedure. Those meters were designed and built in the 50s and 60s to be relatively hard to break, somewhat resistant to EMP, run on D cells and let the civilians know when exposure levels were low enough to leave shelter (the accuracy even when new on those things was rated to be +/- 50% accuracy, though they generally performed much better).

If you want to try the addicting hobby of the CDV meter family ( I have a few), I'd get the 720 if you can find one, they are rare. Open window for beta, where a bunch of your nuclides of concern can be detected.

[mobile1]

This website says that the CDV-715, 710, 720, and all others that ARE NOT the 700, they are survey meters for VERY high levels of radiation that would be lethal within hour.  And it recommends the CDV-700:
    http://www.ebay.com/gds/What-Geiger-counter-is-best-for-your-needs/10000000103552954/g.html

Do you agree?

[HydroDave63]

This website says that the CDV-715, 710, 720, and all others that ARE NOT the 700, they are survey meters for VERY high levels of radiation that would be lethal within hour.  And it recommends the CDV-700:
    http://www.ebay.com/gds/What-Geiger-counter-is-best-for-your-needs/10000000103552954/g.html

Do you agree?

A decent rundown on all of the CDV meters is found here:

http://en.wikipedia.org/wiki/Civil_Defense_Geiger_counters

[doctorbill]

You are right.  If this were the actual dose rate, you would have received a lethal dose (~500 R) by now. 

As to what's wrong with your instrument, I can't tell you.  To provide meaningful data, the instrument must be tested and calibrated.  There could be an electrical short.  You would have to take the instrument to a qualified person to find out.

I suggest that you go to the NRC web site (www.nrc.gov), and access the radiological environmental monitoring reports for the nuclear station near you.

[mobile1]

Thanks for all of your help guys.  I ordered a CDV-700:

http://www.ebay.com/itm/COLD-WAR-CIVIL-DEFENSE-ANTON-CDV-700-GEIGER-COUNTER-RADIATION-DETECTOR-27943-/251286932264?pt=BI_Security_Fire_Protection&hash=item3a81de4b28

[mack70]

Well The good news, your still alive. The bad news, I guess the counter not calibrated or functional.

[mack70]

Thanks for all of your help guys.  I ordered a CDV-700:

http://www.ebay.com/itm/COLD-WAR-CIVIL-DEFENSE-ANTON-CDV-700-GEIGER-COUNTER-RADIATION-DETECTOR-27943-/251286932264?pt=BI_Security_Fire_Protection&hash=item3a81de4b28

The only issue with these items is if you do not have it properly serviced and calibrated, you cannot count on them as a usable tool for measuring exposure/contamination. Which would put you at risk. I would send it for Calibration but who knows how long they will hold calibration, plus you would want a check source to check against calibration. Also not sure if they still do it but Ludlums will retrofit them with a new modern board but I am not sure if its worth it.

If its just to mess with its one thing, but I would not consider it for something that my life would depend on.

Also I would not worry about radiation from a Nuclear power plant. You will get more exposure from Coal plants (ash) and Cigarettes

[jjack50]

You might want to check with your state Civil Defense/Emergency Preparedness/Homeland Security or whatever they are calling themselves now. They certainly had that type of meter years ago and may be able to give you some advice or even calibrate it for you.
You also might consider volunteering for emergency preparedness locally.

[gravy58]

Mobile1,
You don't seem to know enough about radiation much less how to monitor it with any kind of meter. What bothers me is you will miss read an instrument that's not working right in the first place and you'll end up scaring other people for no good reason. The one thing you did right was to throw away the meter. Now listen to the advice that's already been given to you. Call the NRC or some other professional to get the radiological information you want. Leave the meter reading to someone who knows what they are doing.

[SCMasterchef]

Mobile1,

What is scary is that you do not understand radiation fundamentals, their biological effects, and most of all how to know when radiation is harmful.  When folks like you start messing with radiation monitoring equipment not only are you a risk to yourself, you can be a source of very bad information to others.  I agree with those that have told you to leave the meter reading to those that know and understand them.  Playing with meters that have the internal capability of generating 900 V of energy in itself is a risk.  Spending the money and time to get an instrument, you obviously know nothing about, is a waste.  If you want to play with instruments, which are not Tonka Toys, learn something about their purpose, what they measure, how they measure it, and most of all, what do the readings they give you mean.  Also what type of radiation is it measuring, what the risk of that radiation is, and how much of the radiation is actually harmful.  All of this before you even touch a radiation monitoring device.  I don't mess with HAM equipment because I don't know anything about it, so don't mess with radiation monitoring equipment because you do not know anything about it.  All of this said, no disrespect is meant by my comments just information that you may find useful.

[GLW]

Mobile1,
You don't seem to know enough about radiation much less how to monitor it with any kind of meter. What bothers me is you will miss....

Mobile1,

What is scary is that you do not understand radiation fundamentals,.....

You boys are lambasting a user who has not logged on to avail themselves of your deep insights for three months now,...

yup, Mobile1 don't know much about radiacs, he knows about as much about radiacs as you guys know how to search an internet forum to ascertain that the target of your insight even cares to check back in before you hang your ass out in the cyber breeze,....

and don't start on me pal,...

I forgot more about radiacs than you ever knew existed about them,....

[Cecelia]

Hello,
Didnt see your question until today. But here is some help if you still need it.


https://www.fema.gov/media-library-data/20130726-1830-25045-9621/fema_rep_22.pdf


A place (link below) to get it calibrated and put aside your concerns about its ability to perform.  One time and good care of it and you should be good to go for a long time. Once calibrated purchase a Coleman lantern sock at the camping section somewhere. They still sell them. Maybe get extra.   They are radioactive and should give you a count rate of around 10,000 counts per minute. Keep batteries up and use a check source, write the count rate down and track it.  Make a graph if you know how and mark it with date and counts. You will have a background to determine and then subtract that each time for the net counts.  What you will see is a slow decrease in counts over time indicating the decay of the mantel material. which is fine. What you look for is your count rate to be off by more than +/- 20% of the count rate you measure. Weather can effect readings, humidity and temperature. Batteries do not like extreme hot or cold. Neither to probes. Keep that in mind using it. If it passes calibration, they will send it back to you in optimum order. Should be efficiencies on it for energies.  Rule of thumb used by technicians is take gross counts, subtract background, multiply net counts by a 10 factor.  This says the instrument "sees" 10% of what is really there. The final number is used to convert to a quantity. You can find calculators online to plug in the counts to get say a microcurie. Background corrected Counts is really a good answer however.  Background matters if you are measuring a sample. If you are measuring directly with the probe just record what you find and assume a natural background based on a "clean" location close by. Typically 100 counts per minute is a reasonable number.


Here is your calibration link.
http://www.radmeters4u.com/calibrate.htm


Additional info


http://www.civildefensemuseum.com/cdmuseum2/radkits/cdv718.html