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bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  09:28:43  Show Profile  Reply with Quote
I received my new GMC-600+ about two weeks ago and I am delighted with it. A very nice product! My purchase decision was partially based on this excellent forum.

Mostly my 600+ has been sitting in one place on a desk measuring the background here every 15 minutes. My ACPM has converged over 500 measurements to 33.25.

I tried exploring the house and early on some mildly radioactive samples I have but mostly for the past two weeks it has been sitting in the same place in the house, on my desk.

I added myself to gmcmap. There aren't many near me and not many GMC-600+'s.

I seem to be higher than the others I see, although well below any danger level.

I thought I would post these early results for your info and comments.

George

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Older data is to the right on both the above charts.

From one of the other posts here, I got an idea to create a histogram:

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bigfatdaddy

Edited by - bigfatdaddy on 02/20/2020 10:13:53
Reply #1

bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  10:11:30  Show Profile  Reply with Quote
What is the purpose of the little hole next to the USB on the GMC-600+? I don't see it explained in the manual. Maybe I missed that.

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bigfatdaddy
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Reply #2

EmfDev

1243 Posts

Posted - 02/20/2020 :  10:14:50  Show Profile  Reply with Quote
Hi bigfatdaddy, looks like you haven't found anything hot yet XD. Your CPM is slightly higher than GMC 300/320/500+ and even 600 because you counter is more sensitive and can detect alpha radiation. You should compare the dose rate uSv/h or mR/h instead.
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Reply #3

bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  10:23:11  Show Profile  Reply with Quote
Thank you! I don't have anything truly hot :)

Am I correct in understanding that the native device measurement is CPM and the other results are computed? Your GMC map takes input as CPM.

Thanks for your confirmation of what I had suspected about the 600+.

bigfatdaddy

Edited by - bigfatdaddy on 02/20/2020 10:23:55
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Reply #4

EmfDev

1243 Posts

Posted - 02/20/2020 :  10:39:09  Show Profile  Reply with Quote
The extra hole in the device is for analog/audio output. This is only and extra feature that is why it is not included in the manual.

"Am I correct in understanding that the native device measurement is CPM and the other results are computed? Your GMC map takes input as CPM." That is correct, the uSv/h and mR/h computation is based on the sensor and sensitivity.
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Reply #5

bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  11:50:30  Show Profile  Reply with Quote
Thank you.

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bigfatdaddy
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Reply #6

Pilot25dmc

United Kingdom
20 Posts

Posted - 02/20/2020 :  12:58:42  Show Profile  Reply with Quote
For Alpha and Beta, look at CPM.

For Beta and Gamma, look at uSv/hr mR/hr.
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Reply #7

bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  13:21:55  Show Profile  Reply with Quote
I wanted to add that I self tested my house for radon with two passive tests over a six month period last year.

Both tests came back with result half of the limit.

So probably not radon (an alpha source)?

I could shield the detector window with some paper for a month to check the difference?

Also - How does the GMC-600+ response change with temperature? Another building on the property I'd like to test is unheated. That place, my workshop, gets cold. But it does have wifi.

Thank you.

George


bigfatdaddy

Edited by - bigfatdaddy on 02/20/2020 13:45:07
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Reply #8

EmfDev

1243 Posts

Posted - 02/20/2020 :  15:49:56  Show Profile  Reply with Quote
So fast there is no complains or issues for 600+ regarding temperature, for radon detection it is hard. Maybe try to use the timed count feature or food/sample testing feature and get the total/average count for maybe a whole day. If there is a significant difference when you cover the sensor with paper vs not then it could be alpha/radon. But you need to make a lot of tests.
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Reply #9

bigfatdaddy

Canada
34 Posts

Posted - 02/20/2020 :  16:25:23  Show Profile  Reply with Quote
Thanks. Radon is not my prime motivator. Just curious,

bigfatdaddy
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Reply #10

Pilot25dmc

United Kingdom
20 Posts

Posted - 02/20/2020 :  16:53:06  Show Profile  Reply with Quote
For Alpha and Beta, look at CPM.

For Beta and Gamma, look at uSv/hr mR/hr.
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Reply #11

Stargazer 40

USA
370 Posts

Posted - 02/20/2020 :  17:58:24  Show Profile  Reply with Quote
I think if you're looking for Radon, you really need a Radon meter.

The 600 and the 600+ use pancake GM tubes. These tubes have a mica window that allows alpha particle radiation to pass through. They are quite directional regarding alpha radiation and much less directional with higher energy beta and gamma.

I think it is an excellent exercise to cover the case opening of the 7317 LND GM tube with a sheet of paper and record for a week or so and then do the same with the paper removed. You'll get a feel for alpha radiation in your home (hopefully not much will show up).

Stargazer 40

Edited by - Stargazer 40 on 02/22/2020 05:07:06
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Reply #12

bigfatdaddy

Canada
34 Posts

Posted - 02/24/2020 :  05:45:42  Show Profile  Reply with Quote
EmfDev suggested Timed Count. I am trying that without success.

Are there a couple of typos on pg 26-7 of the GMC-600+ manual in the description of setting the Timed count schedule? To me the words don't match the pictures.

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But it says that I don't have to set a schedule. SO I leave the Schedule blank (all zero) and try a one minute timed count. I see the flashing clock icon (which stops after a minute) and I see the message for timed count started. Then it switches to Cancel or Exit and I cannot see the screen pictured in the manual that gives the timed count result. If I select cancel, it announces that timed count has ended and I am back at the main menu.

Need help please. Timed count sounds worthwhile. Thnx.

George

bigfatdaddy

Edited by - bigfatdaddy on 02/24/2020 06:21:28
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Reply #13

EmfDev

1243 Posts

Posted - 02/24/2020 :  09:30:27  Show Profile  Reply with Quote
The Set Schedule is the duration before the actual process starts. If you set it to 0, and then click 1 MinuteCount, it will start immediately. Once started that menu changes to Cancel and Exit. You can see the process in the Home Screen. It will add another mode as Timed Count Mode (e.g Large Font -> Text -> Graphic -> Food -> Timed Count).
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Reply #14

bigfatdaddy

Canada
34 Posts

Posted - 02/24/2020 :  12:56:44  Show Profile  Reply with Quote
EmfDev:
Got it!
I didn't understand about getting back to the home screen. One has to Exit Timed Count at the Cancel or Exit screen and then navigate back out of the menus to the home screen. There, as you said, a *new* display mode of Timed Count has appeared and I can observe the count progress, once that is selected!
I think the GMC-600+ manual description of Timed Count could use some improvement. The device itself is first class!
Thank you for this forum and for your support!
George

bigfatdaddy
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Reply #15

bigfatdaddy

Canada
34 Posts

Posted - 02/28/2020 :  06:29:41  Show Profile  Reply with Quote
My first attempt at trying to discriminate alpha using 100 minute Timed Count over two days. The first day I left the pancake window open, the second day I covered it with two sheets of bond paper. The GMC-600+ was picked up to reset the count numerous times but it was always placed in the same spot aiming in the same direction, straight across the room.
As I am new with the counter, the exercise was worthwhile to see the background here in another way, other than with gmcmap. Throughout the experiment, my gmc-600+ continued to update my gmcmap data while doing timed counts when requested.
Thank you to Stargazer for the suggestion.

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My conclusion is that, at least in my living room, there is next to no alpha radiation. Or is buried in the normal background variation over the day, since the paper shield makes no apparent difference?

I notice now that the Legend in my chart is wrong, the days were 2/26 Open and 2/27 Covered.

bigfatdaddy

Edited by - bigfatdaddy on 02/28/2020 07:47:58
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Reply #16

EmfDev

1243 Posts

Posted - 02/28/2020 :  15:32:26  Show Profile  Reply with Quote
Looks like there is not much of a difference, then you might need a radon meter after all to check for radon. Maybe try for more minutes, like 1 day or so.
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Reply #17

Stargazer 40

USA
370 Posts

Posted - 03/01/2020 :  05:23:57  Show Profile  Reply with Quote
Here is a 2014 video of a Radalert meter compared to a Pro Series 3 Radon meter (I have one of the latter). The Radalert makes use of either an LND end window tube or pancake tube (not clear from the video and current models use both but look different). Given how it is being used I think likely a pancake and likely the same LND7317 used in the 600+. The video shows 6.8 PCi/L which is above the EPA's 4.0 level requiring mitigation. Note that the GM meter is showing a background similar to what we see on 600+. I think the Radon gas effect is being lost in background.

https://www.bing.com/videos/search?q=can+an+alpha+pancake+tube+detect+radon+gas&view=detail&mid=55399EAC3554C7B69F8B55399EAC3554C7B69F8B&FORM=VIRE

So what is with the filter from the air purifier and the high GM meter readings? The electron configuration of the Radon atoms causes it to stick to dust particles! So this video shows the high concentration of radioative dust particles trapped on the filter. Another experiment might be to take a new furnace filter and measure its surface radioactivity with the 600/+ before initial use, then install, and then measure a few days, a week, two weeks, three weeks and a month later. You could then graph the accumlated radioactivity of your trapped dust.

On this filter we're seeing about 2900 CPM from the surface of the filter. With the 7317's 350 CPM/uSv/hr we get about 8.3 uSv/h. I think the meter is set to mR/h which is a tenth of that or roughly .83 mR/h (in the ballpark).

Need to change my furnace filter and will give this a try. Will use a timed count of ten minutes given the response shown in the video. Fun!

Stargazer 40
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Reply #18

bigfatdaddy

Canada
34 Posts

Posted - 03/02/2020 :  04:46:41  Show Profile  Reply with Quote
Result of two 24 hour timed counts in my basement as suggested. Same location as used for the mail in radon tests done two years ago.

Uncovered window
63653 counts

44.2 ACPM
0.126 uSv/h
0.013 mR/h

Covered window (2 sheets bond paper)
56111 counts

38.96 ACPM
0.109 uSv/h
0.011 mR/h

A histogram from my gmcmap data downloaded from the same periods with 15 minute updates:

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I don't know how to properly interpret the results but it seems clear that over a long enough period, I am able to see evidence of some radon in my basement with the GMC-600+ by using paper as an alpha filter.

I will try the furnace filter test next.

This is fun!

George

bigfatdaddy

Edited by - bigfatdaddy on 03/02/2020 05:14:37
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Reply #19

Stargazer 40

USA
370 Posts

Posted - 03/02/2020 :  05:27:16  Show Profile  Reply with Quote
The paper will certainly stop any alphas. The decay chain of Radon also releases betas too. What did your mail in Radon test kit give for pCi/L?

Stargazer 40
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Reply #20

bigfatdaddy

Canada
34 Posts

Posted - 03/02/2020 :  06:15:37  Show Profile  Reply with Quote
My results were 111 and 137 Bq/m3 for a six month duration test. The Canadian guideline for radon is 200 becquerels per cubic metre. I ran two test kits simultaneously, next to each other, to get two samples.

bigfatdaddy

Edited by - bigfatdaddy on 03/02/2020 06:18:44
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Reply #21

Stargazer 40

USA
370 Posts

Posted - 03/02/2020 :  06:34:54  Show Profile  Reply with Quote
Thanks. 1 pCi/L is equal to 37 Bq/m3 so 111, 137 and 200 Bq/m3 are equal to 3, 3.7 and 5.4 pCi/l, respectively.

Stargazer 40
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Reply #22

bigfatdaddy

Canada
34 Posts

Posted - 03/02/2020 :  06:51:28  Show Profile  Reply with Quote
Thank you!

bigfatdaddy
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Reply #23

Damien68

France
241 Posts

Posted - 03/02/2020 :  06:57:46  Show Profile  Reply with Quote
Hi bigfatdaddy, if you have/use vacuum cleaner, after use it you can open it and test the dust bag radiation with your 600+, because as said stargazer_40 on his post, the radon is fixed on the dust.
it is not a quantitative test but a qualitative one. even with my GMC-500+, at me home I have a clear result.

Mastery is acquired by studying, with it everything becomes simple

Edited by - Damien68 on 03/02/2020 06:58:24
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Reply #24

bigfatdaddy

Canada
34 Posts

Posted - 03/02/2020 :  08:20:04  Show Profile  Reply with Quote
I saw your post on the other thread. Thank you Damien68.
Love your tagline!

bigfatdaddy
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Reply #25

mysticforest768

USA
2 Posts

Posted - 09/07/2020 :  13:12:26  Show Profile  Reply with Quote
Hi, I got a GMC600+ a little bit ago, and I can't find any information on what altitude I can take it up to. I know it can't be more then 10,000Ft because of the mica window on the tube. Any ideas? I'm going camping this coming weekend, and I don't want to take it with if I cant ensure that the won't blow out.
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Reply #26

bigfatdaddy

Canada
34 Posts

Posted - 09/08/2020 :  03:01:05  Show Profile  Reply with Quote
The 600+ uses the LND 7317 geiger tube. Here is the spec sheet for the tube https://www.lndinc.com/products/geiger-mueller-tubes/7317
I don't see a spec for the max altitude (min pressure).
Good question if you want to climb a mountain with it.
You might want to ask LND?

bigfatdaddy
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Reply #27

mysticforest768

USA
2 Posts

Posted - 09/08/2020 :  09:24:01  Show Profile  Reply with Quote
i contacted LND and they say im good up to 10k feet. if it blows out the tube is about $150
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Reply #28

GBG12

Canada
69 Posts

Posted - 09/09/2020 :  18:26:46  Show Profile  Reply with Quote
For longer flights, make sure the GM tube is carried with carry-on luggage. Then it will remain pressurized no matter the plane's altitude. The 10,000 foot rating would apply to unpressurized luggage compartments and to small non-pressurized planes.
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Reply #29

blargg

USA
8 Posts

Posted - 10/28/2020 :  19:30:24  Show Profile  Reply with Quote
BTW the most readily available hot item for experimentation I've found is Nu Salt in the grocery store.
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Reply #30

Damien68

France
241 Posts

Posted - 10/30/2020 :  04:33:25  Show Profile  Reply with Quote
I found mine (Nu Salt) in drugstore

Mastery is acquired by studying, with it everything becomes simple
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Reply #31

ullix

Germany
491 Posts

Posted - 10/31/2020 :  00:31:05  Show Profile  Reply with Quote
It looks like "Nu Salt" is just a type of fashion food, where a part of the regular table salt (= NaCl) is replaced with with Potassium salt(= KCl). The mix may vary but what I have seen is an only 30% KCl mix.

You are better off by using 100% KCl (e.g from amazon, lowest grade perfectly ok) or even certain garden fertilizer. See more in my 'Potty Training' article https://sourceforge.net/projects/geigerlog/files/Articles/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download
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