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Glow Girl
USA
2 Posts |
 Posted - 07/20/2017 : 16:00:06
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Hi, I literally opened the box today and started playing with this device. The user manual is terrible and I so far have not found any youtube videos about this model. I have been learning how to work the menu and trying it out on known sources to see how the calibration is. I currently have two Radex 1500+ and a Ludlum Pancake Probe that's in to be fixed now. I bought an SBT-11 tube, bought haven't built anything with it yet, as I am NOT tech savvy and need hubby's help.
It takes my 500+ longer to get a full read than my Radex, but the range is much higher, as the Radex maxes at 9.99 uSv/hr.
A fiestaware plate that I got 59,000cmp on my pancake reads a max of 7809 cmp on the same plate with my 500+. Why is that?
I am happy to meet you all and I've been watching for months and no one was covering the Salt Lake City area on any of the maps I'd seen, so I plan to do that. I've been taking daily readings, every day, for hours with my Radex, but that doesn't show cpm, just uSv/hr or mR/hr.
Is it alright to use for both monitoring for the map and cataloguing and measuring my specimens? I wouldn't do that at the same time. I also have a Mac which might make it difficult to hook into the map. Nice to meet you all and I hope I can get my new 500+ on the map soon. Thank you!
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They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety. |
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| Reply #1
ullix
Germany
1171 Posts |
Posted - 07/21/2017 : 02:47:53
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If I remember correctly the Ludlum Pancake is sensitive to alpha? This means that its Geiger tube has only a thin window and hence is also more sensitive to beta, compared to a GMC500. The latter has the case covering its tube, which absorbs a great part of the betas, reducing the count rate significantly.
Read more in my Potty Training https://sourceforge.net/projects/geigerlog/files/GeigerLog-Potty%20Training%20for%20Your%20Geiger%20Counter-v1.0.pdf/download
Do a test: remove the backplate of the counter (beware of high voltage, see Potty Training!) and compare count rates with and without backplate. |
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| Reply #2
ChrisLX200
United Kingdom
35 Posts |
Posted - 07/21/2017 : 03:20:08
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Welcome! Not many 500+ owners are posting here yet so it's interesting hear your reports. As I understand it the 500+ is something of an upgrade to the 320 series rather than a completely new design, it uses two detector tubes rather than one and has a higher range. However it still cannot detect alpha particles - just beta and gamma like its predecessors. So the 500+ might be described as a background monitor/exposure device rather than a survey device. The pancake probe you have (when fixed!) is certainly suitable for surveying - testing samples for beta gamma and alpha emission, but whether you could connect it the 500+ I don't know. Being able to detect alpha in addition will push the total counts up in many cases which explains the difference you saw with your pancake detector on the fiestaware plate.
Its best to report raw cpm rather than uSv/hr - provided info is also supplied about the detector being used then it's more sensible data where you have no idea what isotope it is you're detecting. |
GMC-300E-plus |
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| Reply #3
Glow Girl
USA
2 Posts |
Posted - 07/21/2017 : 06:04:07
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Thank you everyone. Yes my pancake probe is sensitive to alpha, I always keep the pancake face down or covered, as settling alpha particles can accumulate in the probe.When I measure the plate, which I use as a quick test for calibration, I leave the cover on or put a plastic bag over the probe. So I don't know how much alpha it gets this way. Doing this is important as it's usually measuring my minerals and I place them directly on the probe. I know I won't get an alpha reading when I do that, but some of my minerals have a powdery coating, such as carnotite, that would end up a permanent guest inside the probe. I have a number of radium clocks, some without the glass cover, several in pieces, they are scary to look at to me and the cover of the probe is always off when I measure those. I'm careful not to touch anything to the probe them in any way.
My next question. With my 500, when I measure something, like minerals, watches,etc, I always use a round piece of glass that I cut from the middle of a bottle, so it's ring shaped and 1 cm high to place on top so my Geiger counters don't come into contact with whatever I'm measuring. Is that good enough as a spacer? I'm careful to keep the dirty end down and I wash the glass spacer in borax soap afterward.If any of you have specimens that you measure, what do you use as spacers?
I will read the potty training link, sounds just my thing! I wish my Radex would give readings in more than just uSv/hr or mR/hr but it was the cheapest one that still had good reviews that I could fit discreetly in my purse. When I go to garage sales or thrift stores I can be discreet when I'm looking for things that way. I was asked to leave one place when I was carrying my pancake probe around! I am mildly autistic and my husband mentioned it may have been inappropriate , so hopefully I didn't offend anyone. A lot of pottery made long ago was glazed or colored with uranium, so it's really easy to hide my Radex in the palm of my hand and leave the sound off. |
They who can give up essential liberty to obtain a little temporary safety deserve neither liberty nor safety. |
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Newbie here, GMC 500+
