For those with Geiger counters, post your measurements here!

[sirgonzo420]

Since I started randomly taking radiation readings with my CD V-700 Geiger counter, I have generally observed an average of 17 CPM (0.028 mr/h or 0.283 μSv/h) inside my house in Kentucky.

Today it was raining, so I took a measurement inside, and it was slightly higher than average, as is typical for a measurement inside on a rainy day (at least since Fukushima... heh). The reading was 20 CPM (0.033 mr/h or 0.333 μSv/h).

I then took a paper towel and set it out in the rain until it was wet, at which point I brought it inside and placed it inside a ziplock bag. I then placed the bag on top of the Geiger probe (with the beta window open).

The reading was 36 CPM (0.06 mr/h or 0.6 μSv/h).


Any other GSUSrs who have access to a Geiger counter want to take some measurements and post them here?

[midnight rambler]

Did you ever get that CDV-700 professionally calibrated? Without calibration your results could potentially be off considerably.

(In case you're interested I know of a company that will do it for $60 plus shipping)

[sirgonzo420]

Did you ever get that CDV-700 professionally calibrated? Without calibration your results could potentially be off considerably.

(In case you're interested I know of a company that will do it for $60 plus shipping)


I have not gotten it calibrated myself, but inside the unit was a certificate from the last time it was calibrated, which was in 2000 (pretty recent considering the manufacture date).

When I hold the probe up to the check source on the side of the unit, it reads as expected. There are more modern and more accurate Geiger counters on the market today, but I figure my CD V-700 is decent enough at taking reasonably accurate measurements, and is sufficient for taking relative measurements over time.

Feel free to post the information for the calibration company anyway, for the benefit of the general membership; I assumed calibration would be more expensive than the price you quoted.

I don't think it would be considered spam coming from you.

[gunDriller]

Since I started randomly taking radiation readings with my CD V-700 Geiger counter, I have generally observed an average of 17 CPM (0.028 mr/h or 0.283 μSv/h) inside my house in Kentucky.

Today it was raining, so I took a measurement inside, and it was slightly higher than average, as is typical for a measurement inside on a rainy day (at least since Fukushima... heh). The reading was 20 CPM (0.033 mr/h or 0.333 μSv/h).

I then took a paper towel and set it out in the rain until it was wet, at which point I brought it inside and placed it inside a ziplock bag. I then placed the bag on top of the Geiger probe (with the beta window open).

The reading was 36 CPM (0.06 mr/h or 0.6 μSv/h).


Any other GSUSrs who have access to a Geiger counter want to take some measurements and post them here?


this is a marketable skill.

maybe if we all get experienced we could offer radiation readings ... charge 1 ounce of silver for a reading. show up with 5 different detectors.

we could even have a G-S.us Radiation Reading Society, so that we can honestly say that we are GSUS-RRS certified.

and - it would offer a genuine public service !

[midnight rambler]

I have not gotten it calibrated myself, but inside the unit was a certificate from the last time it was calibrated, which was in 2000 (pretty recent considering the manufacture date).



The original FEMA spec for re-calibration was every four years, then when the budget got cut they moved it out to every six years. The thing about calibration is that unless you've stored it in your own home or office since last calibrated and you *know* how it's been cared for you have no idea what it's been subjected to, i.e. high/low temperatures, thermal changes, humidity, etc. so you really have no idea where it stands. (the fellow in Ohio you got yours from stored the instruments he had in his crawl space and his garage) Lots of CDV-700s on feebay advertised as 'calibrated' when the last calibration was 8 or more years ago.

[beefsteak]

The the "1970s" Geiger Counters sensitive enough to move the needle on radium watch dials and hands on older analog watches and alarm clocks? I've always wanted to ask somebody that, but never knew who.

Can you help, midnight rambler?

Thanks!
Beefsteak

[midnight rambler]

The the "1970s" Geiger Counters sensitive enough to move the needle on radium watch dials and hands on older analog watches and alarm clocks? I've always wanted to ask somebody that, but never knew who.

Can you help, midnight rambler?

Thanks!
Beefsteak


If you're referring to the old Civil Defense geiger counters (the CDV-700 which sg420 posted about) from the early '60s, yes, those are very sensitive in stock configuration. However the key is the Geiger-Muller (G-M) probe and that can be upgraded to something more sensitive such as a pancake probe (which will also detect alpha as well as gamma and beta but don't take it into high altitudes as it will break). The issue with older geiger counters is replacement parts. There are plenty of the CDV-700s around (about 425,000 were manufactured) which can be had for spare parts such as meter movements (no longer made) and 6993 probes (no longer made and the ones now in existence are 50 years old). The CDV-700s are quite robust and will be around for a while still, but I would stay away from any other older geiger counter which you cannot get replacement parts for. The 'standard' is the Ludlum Model 3 and used those are selling for $600 +/- on feebay. You can't go wrong with a working, calibrated Ludlum Model 3. I will have some re-furbed (some dated components on circuit board replaced), re-calibrated CDV-700s available soon. There are other options, but you get what you pay for.

Note difference between 'highly regarded' Gamma Scout and CDV-700 with pancake probe -

http://www.youtube.com/watch?v=I_txeufgt_4

CDV-700 with stock 6993 GM tube, thin end window GM tube, and pancake probe comparison -

http://www.youtube.com/watch?v=ukBpdiA2NvI

[gunDriller]

http://www.vaughns-1-pagers.com/science/victoreen/CDV-7006A-schematic.jpg

looked up a schematic - that's from
http://www.vaughns-1-pagers.com/science/victoreen-cdv-700.htm

http://radgoes.blogspot.com/2011/04/schematic-diagram-of-my-geiger-counter.html
for connecting a Geiger Counter to a PC



http://www.imagesco.com/articles/geiger/fig2web.jpg

basic diagram, from
http://www.imagesco.com/articles/geiger/02.html

[sirgonzo420]

Since I started randomly taking radiation readings with my CD V-700 Geiger counter, I have generally observed an average of 17 CPM (0.028 mr/h or 0.283 μSv/h) inside my house in Kentucky.

Today it was raining, so I took a measurement inside, and it was slightly higher than average, as is typical for a measurement inside on a rainy day (at least since Fukushima... heh). The reading was 20 CPM (0.033 mr/h or 0.333 μSv/h).

I then took a paper towel and set it out in the rain until it was wet, at which point I brought it inside and placed it inside a ziplock bag. I then placed the bag on top of the Geiger probe (with the beta window open).

The reading was 36 CPM (0.06 mr/h or 0.6 μSv/h).


Any other GSUSrs who have access to a Geiger counter want to take some measurements and post them here?


Just a quick note; the rain sample that gave me the 36 CPM (0.06 mr/h or 0.6 μSv/h) reading was obtained from rain that came in from the west, which is the normal direction from which rain comes.

A couple days ago, I took another rain sample, this time from rain coming in from the east (unusual). The sample reading was normal background of 17-18 CPM.

The difference tells me that the radioactivity from the western rain sample is likely from Japan, while the eastern rain sample is "clean".

[sirgonzo420]

Just took another indoor measurement.

16 CPM (0.03 mr/h or 0.27 μSv/h).

[mamboni]

Gunderson says that free air readings are not meaningful. The danger is from tiny "hot particles" whose radiation is averaged out in free air measurements. I have an Oreck electrostatic air cleaner and I've examined the particles collected by the plates under the microscope. The dominant particles are tiny carbon granules and pollen. I assume the former is the result of coal burning furnaces and local wood burning. Apparently, coal burning throws off significant amounts of radioactivity into the environment due to uranium and thorium trace contaminants [in coal]. That said, it would be interesting to suspend these particles in water (results in inky dark fluid), centrifuge down a pellet and take readings on the pellet to see what kind of counts are produced.

[sirgonzo420]

Gunderson says that free air readings are not meaningful. The danger is from tiny "hot particles" whose radiation is averaged out in free air measurements. I have an Oreck electrostatic air cleaner and I've examined the particles collected by the plates under the microscope. The dominant particles are tiny carbon granules and pollen. I assume the former is the result of coal burning furnaces and local wood burning. Apparently, coal burning throws off significant amounts of radioactivity into the environment due to uranium and thorium trace contaminants [in coal]. That said, it would be interesting to suspend these particles in water (results in inky dark fluid), centrifuge down a pellet and take readings on the pellet to see what kind of counts are produced.

Gunderson is right.

My measurements are merely relative readings; a way of tracking "background" radiation over time.

For example, Denver's normal radiation is twice or more what normal is here.

It may not be "safe" now, but if I see Kentucky at Colorado levels, I'll know that relatively and measurably, things have gotten worse.