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 2.GQ Geiger Muller Counter
 Japan, near Fukushima (need help with GMC-600)

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lkj2003223 Posted - 03/18/2019 : 21:54:06
I am interested to purchase my 1st Geiger counter.
I am currently looking at the GMC-600 and GMC-600+ and other cheaper GQ Geiger counters for my long term stay in Japan near Fukushima.

My intention is to use the device to monitor the background radiation and food & water contamination.
Which device would you suggest me to purchase for my intention?

I also have a question for keeping the device safe. I know the GMC-600+ use the Geiger tube LND 7317, which has a very thin mica window.
I heard the thin mica can be very pressure sensitive and can be easily damaged. Does this mean I cannot carry the GMC - 600+ with me on a flight?

How should I handle the device to avoid possible damage to the tube? Any suggestion on protective pouch/case product for the device?

If someone can point some direction/help for me I would very appreciate it.
In return, I will share data/images/results that you might be interested in. My background is electrical & electronic engineering and I am going to be in Japan for business purposes.

Sonicmixmaster Posted - 03/26/2019 : 04:49:24
I bought the 600+ due to it being a bit more directional and as a result I think more sensitive. It has the tube right in the back like many more expensive counters that have the handheld wand with the same pancake tube in them. The 320 model has the tube on the inside on one of the sides and it is open to samples from all sides and to me appears to be less accurate if you want to sample something specific and small. I mostly purchased the 600+ to test for x-ray leakage at work so I know precisely where the leakage occurs between thick steel panels on the x-ray machines.

lkj2003223, I don't know exactly the reason for the ceramic tiles to be so radioactive and it was mentioned to me that I should try to test them with a thick piece of metal or maybe even lead to see if the readings change. I have not done that yet. Need to find some kind of a shielding metal to see if it makes any difference.
ullix Posted - 03/25/2019 : 03:58:45
I'd seriously question the choice of an 600+ counter when you are concerned about robustness of the device. Here is what I commented on a similar question in this post:

The GMC-500+ (the plus-version) has dual tubes, and many issues, reported in this forum. See e.g. here I'd strongly recommend against it for your purposes (the 2nd tube is MUCH less sensitive, so no help at all).

The GMC-500 (the non-plus-version) and the 300 and 320 series are functionally equivalent; they all have only a single tube, always a M4011. The memory is big enough even in the 64k-only in the 300E+; I don't see WiFi, as it is implemented, an advantage. While the 3xx series clock is notoriously off, the 500 has a more precise real-time-clock. However, in my unit this clock broke right away, and so I can't make any history recording in the 500, while it at least works with the 300, although the timing is off.

The one clear advantage of the 500 is the bigger display of 128x64 versus 128x32, and operating the buttons a bit smoother. This is worth considering for convenience and handling.

So, my suggestion: get a 500 NON-PLUS! and spend the saved money on a Smart Geiger Pro (SGP-001) reviewed here:

This pair of devices would be greatly complementing, and the latter device would be of greater interested to less technically inclined users.

Since you are expecting higher dose rates, optimizing the sensitivity of your devices is not the prime target.
lkj2003223 Posted - 03/24/2019 : 16:06:48
Thank you Sonicmixmaster and EmfDev for your reply. My worry is the LND-7317 can be damaged by the change in pressure. Eg, big pressure change due to high altitude and rapid pressure change due to door slam... etc. I was wondering if there a needed for a pressure stabilise protective case.

4.21 uSv/h? Isn't that a little high? Why is it radioactive in the 1st place??

I will not travel to Japan before summer but I let you know as soon as I start travelling! I ordered the 600+ just now, very looking forward to learn more about radiation and Geiger counter.
I might need some help to learn how to turn the Geiger counter once it arrives.
My plan is to get some KCI to play with 1st.
I also live in a high radon concentration area right now. It will be interesting if I manage to detect it.
EmfDev Posted - 03/19/2019 : 09:00:00
Thank you Sonicmixmaster for answering his question. Just to add, the grid is Aluminum. It is there to help protect the tube for some contamination and so you just don't accidentally poke the inside. According to support, they have been shipping some 600+ via air and so far there are no complaints of abnormal readings or 0 CPM from customers with those units.
Sonicmixmaster Posted - 03/19/2019 : 08:13:47
I have the 600+, it has protective plastic grid over the tube and you wont have a problem unless you start sticking things in there on purpose. I keep it in its original plastic anti-static bag if I want to carry it outside or put it my backpack to take places. I read somewhere that the tube can be damaged if it gets wet so I make sure it is not exposed to water drops and rain if you use it outside. There is no problem bringing it on a flight either as I work at the airport operating x-ray machines. Since you plan on flying I would like to know what background radiation levels are you getting at cruising altitude during your flight. If you can share the readings that would be great! Thanks. If you have other questions regarding the 600+ then post here and I will try to answer. Here is an image I just took of mine with a usb flash drive to show you the grid spacing.
And here is the front picture from months ago when I measured radioactive ceramic tiles in my friends bathroom

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