| T O P I C R E V I E W |
| c27r |
Posted - 06/23/2014 : 13:48:08
Hi,
I am considering purchasing a GMC 320 to detect and measure x-ray and gamma radiation. As X Rays include a range of energy levels I wanted better understand the full range of harmful energy levels the GMC 320 can detect. I found the link below and the quote below from within the manual:
http://www.gqelectronicsllc.com/GMC320UserGuide.pdf
"Range of registered X-ray radiation energy MeV 0.03 to 3.0"
It seems to me that this is well above the energy levels for x ray and that there is a significant gap in what the device will detect. Is this an error in the manual or in my understanding of what the manual is trying to communicate? Please clarify.
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| 16 L A T E S T R E P L I E S (Newest First) |
| Alchemy2 |
Posted - 09/29/2014 : 21:47:58
C27r:
Please see my most recent posting on the SBT-11A pancake tube. I am able to read very low energy Bremsstralung radiation (X-rays) off a Tritium keychain (beta light). H-3 betas are 18.6 keV, and too weak to penetrate much the acrylic encapsulation it has. I am reading without protective screening over 100CPM off this light. Even mean X-ray energy is <18 keV, so you might be able to read very soft X-radiation with this setup, or using a similar pancake supplementary tube.
The SBT-11A ran me around $35 on eBay off a Bulgarian seller a few weeks ago. It is very easy to replace this tube into the unit, or even run it as an auxiliary if you wish.
Let me know...
Alchemy2 |
| ZLM |
Posted - 09/17/2014 : 22:18:55
Do you know what is your x-ray energy level in keV unit?
and what is your exposure time on Geiger Counter (how long)?
Yes. You need a RMA. Please write to support@gqelectronicsllc.com. |
| c27r |
Posted - 09/17/2014 : 10:19:16
"If it does not work, you can return it to get 100% price refund."
ZLM, How can I get the 100% price refund? Do I need an RMA? |
| c27r |
Posted - 09/17/2014 : 10:08:37
I tested at 80 Kv and 115 Kv. The unit did not register any change. |
| ZLM |
Posted - 08/14/2014 : 07:25:28
It seems this problem is related to the hardware problem. The unit should not in "Charging" if you disconnected unit from a USB cable. This should not be a big problem. Write to support@gqelectronicsllc.com for warranty.
Have you test it with your X-Ray machine? |
| c27r |
Posted - 08/13/2014 : 08:23:47
The unit will not fully shut off. When the unit is shut down it says "Charging" even though the unit is unplugged. Consequently, the battery continues to discharge and only lasts a day. This severely limits the unit's usefulness. Can this be fixed? |
| c27r |
Posted - 06/26/2014 : 05:28:29
ZLM, Thank you for your response. I will take you up on your 100% price refund and give it a try.
Alchemy, Thanks again for your response. My question is important and sincere. I do stand by my posts. |
| Alchemy2 |
Posted - 06/25/2014 : 15:53:09
I personally don't understand the fuss. This is sold as a NUCLEAR radiation detector. In the energy ranges stated in the manual, GQ is actually correct in their assessment of this unit. I did some reflection on this after replying to the c27r fellow asking all the X-ray questions, and TECHNICALLY the manual is correct. I am wondering if this query is truly a curiosity, or an attempt by some competitor to discredit the maker of these units? It does happen on these forums in other hobbies and interests, like astronomy equipment. I have seen this type of fuss before.
GM tubes have lower limits on their sensitivities, and trying to quantify the sensitivity of the unit on the low end is just splitting hairs in a way. It will see some X-radiation, and certainly sees beta and gamma radiation as well. So, it does work as advertised. It is harder to get isotopes that can have ONLY gamma energies, and even then, low end gamma around 0.1MeV may be harder to quantify, other than being detected...
For the price, this is a nice piece of kit. If one needs to make determinations on sensitivities, then they should do some experiments. I doubt that the M4011 tube with the settings from the factory would be more than maybe even 5% efficiency in the low end of the energy window anyway.
If one needs a better detector for that region, then a Scintillation probe, or X-radiometer should be procured. Geez. |
| Alchemy2 |
Posted - 06/25/2014 : 15:40:50
You're right of course. Hard X-rays usually limit to ~200keV and then you're into gamma ray energies. There's a bit of a transition of sorts, but I don't know how soft the rays would be before the unit is insensitive. Technically, X-rays are electron energies, and gammas are nuclear energy transitions, so in some ways the manual is valid.
If one took a 1MeV electron stream and hit a metallic target in near-vacuum, it technically IS an X-ray source, even though it does have enough energy to qualify as a gamma photon. I always found that interesting in that region of the spectrum.
Nonetheless, according to standard definitions, I should have been more clear. I do know that several folks have had their unit on power saving mode through airport security scans and have definitely had a significant spike in the CPM levels. As to how to quantify this, without more information, it's all but impossible, but these energies are usually in the 80-160keV ranges. So, harder X-rays are detected for sure.
I do also agree with you that the manual is poorly written with regards to distinguishing the photonic energies. ANY high energy photon in the lower ranges to 3MeV should be detectable. How sensitive the unit is to those in the 30-50keV range, no idea. That's why I suggested a test may be in order.
Hopefully, I have clarified one or two more things. If ZLM can find out that would be great.
quote:
Originally posted by c27r
Alchemy2,
I appreciate your response. Thank you for taking the time.
I'm not looking for a dosimeter or for the device to report energy levels. I'm just looking for the range of energy levels this device will pick up. I think that is a reasonable and important question to have answered. I, too, looked at the numbers you are looking at in the manual and am rejecting them as false for two reasons:
1. X-Rays start at 100eV and (depending on who you read) only go up to either 10keV or 100keV. The definition at the upper end is fuzzy (like I said, it depends on who you read). But either way, if the manual is correct, then this device doesn't detect x rays at all or a most it doesn't detect significant (and dangerous) portion of the x ray spectrum.
2. Look at the range for Gamma in the manual and compare it to the range for x-ray described in the manual. It makes no sense. It must be a typo. Regardless of who you read, x-rays don't go from .03 to 3.0 Mev and also do not extend both above and below Gamma. Why would any product engineer or technical writer write that into the manual. It doesn't make any sense.
I think at this point, I would really like a product engineer from the manufacturer to tell us (with a degree of confidence) the ranges of energy levels the device will pick up.
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| ZLM |
Posted - 06/25/2014 : 10:50:13
I do not have other x-ray spectrum coverage data in hand. If you want to use it in soft x-ray range, then you can try it.
I believe the tube is more sensitivity to the higher energy x-ray than lower energy x-ray .
If it does not work, you can return it to get 100% price refund.
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| c27r |
Posted - 06/25/2014 : 10:08:31
ZLM, That's one data point at the very end of the hard x-ray spectrum very close to gamma. Do you have any data for the other end of the x ray spectrum? |
| ZLM |
Posted - 06/25/2014 : 08:44:45
The unit is been confirmed to detect the security inspection x-Ray, which is about in range 100Kev - 300Kev.
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| c27r |
Posted - 06/25/2014 : 06:00:35
Alchemy2,
I appreciate your response. Thank you for taking the time.
I'm not looking for a dosimeter or for the device to report energy levels. I'm just looking for the range of energy levels this device will pick up. I think that is a reasonable and important question to have answered. I, too, looked at the numbers you are looking at in the manual and am rejecting them as false for two reasons:
1. X-Rays start at 100eV and (depending on who you read) only go up to either 10keV or 100keV. The definition at the upper end is fuzzy (like I said, it depends on who you read). But either way, if the manual is correct, then this device doesn't detect x rays at all or a most it doesn't detect significant (and dangerous) portion of the x ray spectrum.
2. Look at the range for Gamma in the manual and compare it to the range for x-ray described in the manual. It makes no sense. It must be a typo. Regardless of who you read, x-rays don't go from .03 to 3.0 Mev and also do not extend both above and below Gamma. Why would any product engineer or technical writer write that into the manual. It doesn't make any sense.
I think at this point, I would really like a product engineer from the manufacturer to tell us (with a degree of confidence) the ranges of energy levels the device will pick up.
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| Alchemy2 |
Posted - 06/24/2014 : 16:36:13
c27r:
Gamma energies apparently are in the 0.1-1.25 MeV regime, and x-ray from 0.03-3.0 MeV. Since both are EM radiation, then really X/y-Rays are detectable from 0.03-3MeV.
Regardless, the ENERGY of the event would not be discernible using this device, since anything in the event "window" of energies, will trigger a counting event (with an approx. 20% sensitivity, or 20% chance in detection typical with GM detectors).
So the long answer is: I would safely say in the 0.05-3MeV range, the device will respond to X and gamma rays. The sensitivity would be non-uniform, so expect the best sensitivity or counting efficiency to be most likely in the 0.2-1.5MeV regime. Only way to know for sure is to test this with a range of X-ray energies in a lab.
If you are trying to calibrate this instrument to act as more of a dosimeter or dosage meter of sorts, you could do this in two ways:
1) look up X-radiation and dosage-equivalent numbers that are used to get uSv dosage or rates of uSv/h or mR/h.
2) Use a known X-Ray source with an average energy within this window (100keV or 0.1MeV is good - with appropriate caution, of course!) and read CPM above background to then calibrate this to what you are looking at for dosage.
If you want the event to trigger and then have it tell you: that was a 120keV event, no dice. A scintillation detector coupled to a spectrometer is the only way to get a spectrum of energies. Much more expensive than this unit, and requires some significant nuclear knowledge beyond the scope of most folks' due to the nature of the results. It would be awesome though.
If there's more I can help you with in regards to a more (semi) quantitative answer, please let me know. 90+% of the folks here are not nuclear scientists. Neither am I per se, but had 2 years of it during my PhD program in Physical chemistry, and I delat a lot with X-radiation as well. I may be able to help. |
| c27r |
Posted - 06/24/2014 : 11:07:55
I think you are misunderstanding the question. I am not looking for the device to tell me the energy level of the radiation. I am looking for some specifications to tell me what energy ranges the device is sensitive to. Do you have this information?
If you don't have this information, what is this trying to tell me? -> "Range of registered X-ray radiation energy MeV 0.03 to 3.0" |
| ZLM |
Posted - 06/24/2014 : 10:10:14
In the manual has no coverage detection of energy level. Only the sensitivity: 0.1-1MeV.
The unit is able to detect Beta, Gamma, X-Ray and then gives the estimated dose reading in uSv.h or mR/h.
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