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jeff_becker@msn.com
USA
9 Posts |
 Posted - 11/15/2023 : 08:13:04
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I just purchased the new GMC-800 for safety in the event of a nuclear exchange, dirty bomb or accident, after holding off on purchasing the GMC-600+ due to its poor/dated interface and apparent fragile case. I have not had any problems with the GMC-800, but I have no way of knowing its actual accuracy and response time in measuring radiation. I have been concerned with its accuracy and performance due to its very low price. Just yesterday I read the Amazon review of the GMC-800 (listed below) and I am now very concerned that I made a bad decision. Any thoughts?
Scarlyn
1.0 out of 5 stars Too good to be true, very disappointed.
Reviewed in the United States on November 11, 2023
Verified Purchase
I am a Chemistry PhD. student currently working in a lab with radioactive materials.
Long story short: I wanted to buy a personal Geiger counter for me to take home, but that it can also function properly in the lab.
I found the GQ GMC-800 very appealing because of the display and price. But it was too "cute" to be true.
When I received it, I was home, so I couldn't test it properly. The reading was an average of 12 to 20 CPM (background radiation)
The next day at the lab, I took it near the fume hood, where normally our Ludlum survey meter goes crazy, but the GQ GMC-800 stayed the same,
nothing happened. I was getting background radiation levels on the GMC-800. So we tested it by putting it on top of a Uranium glass and leaving it there,
and after about 15 minutes, we got a max reading of 80 CPM, compared to our other devices (including the ludlum), which immediately went up to 300 CPM
on the same Uranium glass.
Now that's not good at all! And even if it was only my device that came defective, it makes me wonder about the overall quality and reliability of this GQ GMC-800. I'm really disappointed.
So, I'm returning this one for sure. |
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| Reply #1
ullix
Germany
1171 Posts |
Posted - 11/16/2023 : 01:19:54
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I'd be surprised if the GMC-800 were as bad as you say. I suspect it is more a lack of understanding of measurements!
Most often the cause is comparing two instruments where one is - by its design - more sensitive to betas than the other, and the rdioactive source being rich in betas.
I have not had a GMC-800 in hand, but by the pictures of it it looks like having a more sturdy case than its older GMC siblings. If true it would mean that its sensitivity to betas is further reduced.
A good reference to compare counters is KCl, as its radioactivity, while weak, is the same everywhere on earth. It is emitting betas more stronger than gammas.
I suggest my "Potty Training" article, which has the details; download from: https://sourceforge.net/projects/geigerlog/files/Articles/
It involves removing the backplate of the counter to expose the "naked tube" to the KCl source.
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| Reply #2
ihab17
Italy
218 Posts |
Posted - 11/16/2023 : 03:24:35
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| The GMC-800 detects Beta and Gamma, but not Alpha particles as far as I know. Uranium decays into Thorium by emitting an Alpha particle which your GMC-800 can't detect. If you want to detect Alpha particles, your only GMC solution is the GMC-600+ |
Edited by - ihab17 on 11/16/2023 08:35:11 |
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| Reply #3
EmfDev
2250 Posts |
Posted - 11/16/2023 : 15:26:56
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| The review is either from a competitor or a lack-of-radiation-knowledge-PhD-student-who-will-soon-fail-his-degree:). THE GMC-800 has passed the USA NRC/NIST Calibration standard. This guy is comparing a pancake tube and a ~$1000 detector to an entry level geiger counter that cannot detect alpha. Instead of comparing the uSv/h, he even instead compared the CPM. |
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| Reply #4
jeff_becker@msn.com
USA
9 Posts |
Posted - 11/17/2023 : 10:39:23
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| You are missing my point. If a $1,000 Geiger counter and one that also detects Alpha radiation is what is needed to protect me and allow me to greatly reduce my chances of a level of exposure high enough to impact my health in the event of 1) a nuclear accident, 2) dirty bomb or 3) a nuclear exchange/war between the US and another nuclear power, the price of the Geiger counter is irrelevant. I made my post stating that I was considering the GMC 600+ (which measures alpha) and am willing to pay whatever price is necessary (within reason) to meet my stated requirements. I also stated that I was concerned that I paid too little for the GQ GMC 800 and was "concerned with its accuracy and performance due to its very low price." If a Geiger counter costing $600 to $1,000 is what is needed to meet my requirements, I am willing to pay that. However, if I don't need to pay that amount to meet my requirements, I don't want to unnecessarily waste money either. |
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| Reply #5
EmfDev
2250 Posts |
Posted - 11/17/2023 : 13:45:07
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| The GMC-800 is good choice for your purpose. If any of those events you listed happened, the radiation will be much higher. The GMC-800 will be able to pick up the radiation. |
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| Reply #6
ullix
Germany
1171 Posts |
Posted - 11/18/2023 : 01:52:51
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quote:
The GMC-800 is good choice for your purpose. If any of those you event listed happened, the radiation will much higher. The GMC-800 will be able to pick up the radiation.
I concur.
And read the "Chemistry PhD. student" report carefully - lots of indications that this guy is lacking competency!
And after all, even better than a Geiger counter for your purposes is a battery powered radio. |
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| Reply #7
UnstableIsotope
USA
67 Posts |
Posted - 12/05/2023 : 14:58:48
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quote:
Originally posted by EmfDev
The review is either from a competitor or a lack-of-radiation-knowledge-PhD-student-who-will-soon-fail-his-degree:). THE GMC-800 has passed the USA NRC/NIST Calibration standard. This guy is comparing a pancake tube and a ~$1000 detector to an entry level geiger counter that cannot detect alpha. Instead of comparing the uSv/h, he even instead compared the CPM.
I read that same review on Amazon and thought the same thing. 
Really? This self-impressed PhD student apparently doesn't know that the Ludlum will pickup Alpha while any glass tube device will not. Doh! 
Frankly, I really hope the GQ 800, at least in terms of it's more pro looking, and hopefully more durable, exterior is the way GQ continues to move it's product line.
I already had a couple cheap Geigers before I picked up the 500+. While neither compete with the 500+ in terms of features and functions, the FNIRSI GC-01 presents an up-to-date, professional design with a very responsive UI, great screen, etc. Too bad it's locked into a 10s sliding averaging window that causes it to overshoot background estimates by quite a bit. The FNIRSI also oddly omits an audible click feature instead indicating individual events only on an LED.
I sincerely hope GQ will continue to update it's aesthetics and usability for new products. I honestly considered the 800 before purchasing the 500+ purely for technical reasons. I really wish the 500+ was packaged like the 800. |
Edited by - UnstableIsotope on 12/06/2023 06:17:36 |
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| Reply #8
ihab17
Italy
218 Posts |
Posted - 12/06/2023 : 06:57:34
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quote:
Originally posted by UnstableIsotope
I already had a couple cheap Geigers before I picked up the 500+. While neither compete with the 500+ in terms of features and functions, the FNIRSI GC-01 presents an up-to-date, professional design with a very responsive UI, great screen, etc. Too bad it's locked into a 10s sliding averaging window that causes it to overshoot background estimates by quite a bit. The FNIRSI also oddly omits an audible click feature instead indicating individual events only on an LED.
I sincerely hope GQ will continue to update it's aesthetics and usability for new products. I honestly considered the 800 before purchasing the 500+ purely for technical reasons. I really wish the 500+ was packaged like the 800.
Personally, I wouldn't go for this cheap Chinese product (FNIRSI GC-01), with extreme commercial (non-scientific) idiotic and childish marketing. Here is the official link which you can find also on AliExpress or AliBaba. Scroll down until you the the image in Nuclear Radiation Dose Hazards at a Glance... they measure the dose by RUM!!!! Rum? Vodka? Or did they mean REM? If they don't even know how to write the scientific unit, go figure if I even accept a device like this even if it was a gift! The word measuring becomes mea-suring! Come on! It is a toy, you can't trust it!
https://usa.banggood.com/FNIRSI-GC01-Geiger-Counter-Nuclear-Radiation-Tester-Food-and-nuclear-sewage-Test-Professional-Marble-Radiation-Ionization-Personal-Dose-Alarm-Radioactive-Tester-p-1973818.html?imageAb=2&akmClientCountry=IT&cur_warehouse=CN&a=1701873419.1607&DCC=US¤cy=EUR&akmClientCountry=IT
For me, a Geiger Counter is a scientific instrument, and if you need a good one, you have to spend money, especially if you have the need to detect Alpha particles. A scientific instrument does not have to be appealing esthetically, it simply has to work and do what it is supposed to do. The esthetics comes much later after the product has been tested and demonstrates reliability and accuracy. GQ instruments aren't esthetically appealing as this one above, and they might not be reliable and accurate as a 2K euro/dollar professional device, but at least you have the possibility to write here on their forum, get firmware updates, and ask questions. Try doing that on ALiExpress or directly to the Chinese manufacturer... good luck with that!
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| Reply #9
ihab17
Italy
218 Posts |
Posted - 12/06/2023 : 06:58:20
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quote:
Originally posted by UnstableIsotope
I already had a couple cheap Geigers before I picked up the 500+. While neither compete with the 500+ in terms of features and functions, the FNIRSI GC-01 presents an up-to-date, professional design with a very responsive UI, great screen, etc. Too bad it's locked into a 10s sliding averaging window that causes it to overshoot background estimates by quite a bit. The FNIRSI also oddly omits an audible click feature instead indicating individual events only on an LED.
I sincerely hope GQ will continue to update it's aesthetics and usability for new products. I honestly considered the 800 before purchasing the 500+ purely for technical reasons. I really wish the 500+ was packaged like the 800.
Personally, I wouldn't go for this cheap Chinese product (FNIRSI GC-01), with extreme commercial (non-scientific) idiotic and childish marketing. Here is the official link which you can find also on AliExpress or AliBaba. Scroll down until you see the image in Nuclear Radiation Dose Hazards at a Glance... they measure the dose by RUM!!!! Rum? Vodka? Or did they mean REM? If they don't even know how to write the scientific unit, go figure if I even accept a device like this even if it was a gift! The word measuring becomes mea-suring! Come on! It is a toy, you can't trust it!
https://usa.banggood.com/FNIRSI-GC01-Geiger-Counter-Nuclear-Radiation-Tester-Food-and-nuclear-sewage-Test-Professional-Marble-Radiation-Ionization-Personal-Dose-Alarm-Radioactive-Tester-p-1973818.html?imageAb=2&akmClientCountry=IT&cur_warehouse=CN&a=1701873419.1607&DCC=US¤cy=EUR&akmClientCountry=IT
For me, a Geiger Counter is a scientific instrument, and if you need a good one, you have to spend money, especially if you have the need to detect Alpha particles. A scientific instrument does not have to be appealing esthetically, it simply has to work and do what it is supposed to do. The esthetics comes much later after the product has been tested and demonstrates reliability and accuracy. GQ instruments aren't esthetically appealing as this one above, and they might not be reliable and accurate as a 2K euro/dollar professional device, but at least you have the possibility to write here on their forum, get firmware updates, and ask questions. Try doing that on ALiExpress or directly to the Chinese manufacturer... good luck with that!
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Edited by - ihab17 on 12/06/2023 07:00:05 |
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| Reply #10
Jadeye
34 Posts |
Posted - 12/06/2023 : 07:54:11
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| @ihab17: I like how the alarm modes are translated as "glitter" and "shock", it could be an interesting experience, if the "glitter" would sprinkle the user with glitter, and the "shock" would deliver an (electric) shock. :D |
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| Reply #11
ihab17
Italy
218 Posts |
Posted - 12/06/2023 : 09:33:32
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quote:
Originally posted by Jadeye
@ihab17: I like how the alarm modes are translated as "glitter" and "shock", it could be an interesting experience, if the "glitter" would sprinkle the user with glitter, and the "shock" would deliver an (electric) shock. :D
Not to mention the word Symptoms becomes Sympatoms |
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| Reply #12
UnstableIsotope
USA
67 Posts |
Posted - 12/06/2023 : 09:55:06
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quote:
Originally posted by ihab17
quote:
Originally posted by UnstableIsotope
I already had a couple cheap Geigers before I picked up the 500+. While neither compete with the 500+ in terms of features and functions, the FNIRSI GC-01 presents an up-to-date, professional design with a very responsive UI, great screen, etc. Too bad it's locked into a 10s sliding averaging window that causes it to overshoot background estimates by quite a bit. The FNIRSI also oddly omits an audible click feature instead indicating individual events only on an LED.
I sincerely hope GQ will continue to update it's aesthetics and usability for new products. I honestly considered the 800 before purchasing the 500+ purely for technical reasons. I really wish the 500+ was packaged like the 800.
Personally, I wouldn't go for this cheap Chinese product (FNIRSI GC-01), with extreme commercial (non-scientific) idiotic and childish marketing. Here is the official link which you can find also on AliExpress or AliBaba. Scroll down until you see the image in Nuclear Radiation Dose Hazards at a Glance... they measure the dose by RUM!!!! Rum? Vodka? Or did they mean REM? If they don't even know how to write the scientific unit, go figure if I even accept a device like this even if it was a gift! The word measuring becomes mea-suring! Come on! It is a toy, you can't trust it!
https://usa.banggood.com/FNIRSI-GC01-Geiger-Counter-Nuclear-Radiation-Tester-Food-and-nuclear-sewage-Test-Professional-Marble-Radiation-Ionization-Personal-Dose-Alarm-Radioactive-Tester-p-1973818.html?imageAb=2&akmClientCountry=IT&cur_warehouse=CN&a=1701873419.1607&DCC=US¤cy=EUR&akmClientCountry=IT
For me, a Geiger Counter is a scientific instrument, and if you need a good one, you have to spend money, especially if you have the need to detect Alpha particles. A scientific instrument does not have to be appealing esthetically, it simply has to work and do what it is supposed to do. The esthetics comes much later after the product has been tested and demonstrates reliability and accuracy. GQ instruments aren't esthetically appealing as this one above, and they might not be reliable and accurate as a 2K euro/dollar professional device, but at least you have the possibility to write here on their forum, get firmware updates, and ask questions. Try doing that on ALiExpress or directly to the Chinese manufacturer... good luck with that!
Agreed, their English is lacking, but still much better than my Mandarin. It was the first GC I picked up for grins and while the marketing is sketchy, the product design appears to be reasonably sound. Also, within the limits of it's 10s estimation window and an unvented case, the GC-01 appears to function as expected. The PCB layout is clean and well done. The case is well designed with a full silicone bumper surrounding the edges which would absorb small bumps and drops instead of transmitting that energy to the fragile GM tube. The display is excellent and updates quickly. It even comes with a nice, bubble-free screen protector installed! The interface is also very responsive. These are all good things that every product like this should have as design goals.
While my 500+ is much more a real instrument, it doesn't have to lack the characteristics I list above to be so. The GC user interface is very dated and honestly pretty bad in some areas. Menu items are inconsistently implemented and some are very cumbersome, like entering a Wifi password or changing a CPM alarm or the MEDIUM/HIGH thresholds. Some menu items are grammatically incorrect as well. The buttons are not properly polled and respond inconsistently. These things could be improved while still remaining a more accurate measuring instrument.
I really like all the fine-grained, nerdy adjustments that are available on my 500+. The level of control is wonderful compared to simple devices. However, all these features should be consistently implemented to produce an intuitive and responsive user interface. At this point, that is not the case. |
Edited by - UnstableIsotope on 12/10/2023 10:09:10 |
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| Reply #13
Tony81269
USA
68 Posts |
Posted - 08/17/2024 : 16:38:23
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| I haven't bought one of these GQ brand meters but I do have serious questions about calibration. I work in the Well Logging industry and I deal with the NRC on at least a yearly basis. Our survey meters have to be calibrated to certain standards in labs. There are specific requirements. For analog meters it is "Accurate to 20%, and must be calibrated on each scale twice, at approximately 1/3 and 2/3 of full scale deflection" an on digital models it is "must be calibrated at one point per decade over the range that will be used". Must be done every 6 months. So, I look at the description on Amazon and it says they will give you a certificate upon request and then they say something about having a third party to do it for extra money. I find this confusing. Is it really calibrated to NRC standards when you buy it? Or do you have to pay to have that done?The lack of information leads me to think these aren't really professional instruments. Anyone ever try to have one of these meters calibrated at a licensed place? |
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| Reply #14
Stargazer 40
USA
431 Posts |
Posted - 08/17/2024 : 17:21:45
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I have GMC 500, 500+(2), 600, 600+ and now 800 and the Pro Radon 2-1 meter to test. I have posted numerous comparison tests here using lab radioactive sources and maxed out most of these meters (from a distance of course). I have compared my GMS meters with Mazur PRM-9000 $700 meter and calibrated them to match. I've also built GM meters with Russian glass and pancake tubes and torn apart every meter except the Mazur which wasn't mine to see what made them tic. They are more fully featured than many and as EmDev says you can get them certified. Never compare based on CPM! Use uSv or mR setting and then get a range chart. Different meters measure different ranges. I built cards that properly place the tubes with range of interest. This one compares the two tubes in the 500+ with govt CD-V 700 and CD-V 717. On the right the damage levels.
Some of my testing up in Sticky Posts. Deadtime Calibration shows the type of tests I run.
These meters work great and are consistent performers. They provide good value against anything else out there in my opinion. |
Stargazer 40 |
Edited by - Stargazer 40 on 08/18/2024 16:12:37 |
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| Reply #15
Tony81269
USA
68 Posts |
Posted - 08/17/2024 : 19:13:52
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| These meters probably do perform well and calibration probably is accurate. At the end of the day, I have to have a certificate that says the meter was calibrated at a lab and under certain NIST standards. If my guys don't have that certificate in their trucks then NRC gives us a violation. I personally am required to have copies of these certificates in our company files. If we have had the meter for more than three years then I am required to have copies of all the calibrations that were done during that period or another violation. I'd really like to try one of these but I could only use it for testing purposes unless I can get a lab to calibrate it. I might buy one anyway just to see |
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| Reply #16
Tony81269
USA
68 Posts |
Posted - 08/18/2024 : 11:13:50
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quote:
Originally posted by ihab17
The GMC-800 detects Beta and Gamma, but not Alpha particles as far as I know. Uranium decays into Thorium by emitting an Alpha particle which your GMC-800 can't detect. If you want to detect Alpha particles, your only GMC solution is the GMC-600+
I understand that it would not read alpha coming from Uranium but wouldn't it still detect the gamma emissions? |
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| Reply #17
Stargazer 40
USA
431 Posts |
Posted - 08/18/2024 : 16:13:41
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| I updated my post above to add the chart comparing meter types with uSv and mR. |
Stargazer 40 |
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| Reply #18
Stargazer 40
USA
431 Posts |
Posted - 08/22/2024 : 02:49:57
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| Yes, beta and gamma. |
Stargazer 40 |
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| Reply #19
Stargazer 40
USA
431 Posts |
Posted - 09/07/2024 : 07:58:01
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If the OP wants alpha, then the 600+ is a wonderful meter. I have both the 600 (SBT-11A) and the 600+ (LND-7317) and appreciate the added alpha feature at the expense of higher end response (deadtime calcs really are necessary with these windowed GMs). But, if he wants a meter that can tell him when things are getting bad, then the GMC-800 will fit that bill sans the alpha component.
Like many of you that are working through the best way to use a GMC-800 GM meter I remain so very pleased that it isn't a 500+ type meter (and definitely not a 600+ meter). In this forum we spent a lot of time over the last couple of years trying to fully understand these GQ meters and ensure that they are matching in performance much more expensive meters. While operating system and working through the menus of the 500/500+, 600/600+ takes a while to become proficient at, the flexibility of those adjustments is really nice for tweaking those instruments for individual use as either sample or survey meters. And especially the 600/600+ provides for alpha so you can get all three in a very powerful tool for measuring the environment.
The GMC-800 is not the same type of meter. It is a use it out of the box meter with features that make it easy to use with minimal interaction. A friend who acquired one of these (his first meter) was telling me how much he liked the preset alarms and overall useability. He takes it pretty much everywhere in the wonderful see through case. GQ has built this meter for those wanting something simple to use and have confidence that you're seeing a valid reading for the environment you're in. It still retains however the ability to be made more credible as the six calibration points allow for certification by NRC.
One of our forum members is going through the certification process and sharing his experience. Can't wait to see the results. Still, how much do we really need to be concerned about nailing the high end of the curve (which really is what is in question on a deadtime delay affected reading)? We will understand better when we see his lab certified CPM conversion numbers for each of the six calibration points. Doing the math for the tube and using a deadtime delay of 90usec, I see the first four points as under 6% error for deadtime correction. Five is at 12%. Only point six is beyond 20%, under reporting at 24%. This means that for 2000 uSv it is reading 24% fewer counts per minute than are actually occurring. GQ feels this tube's response is pretty much linear and if your standard is 20% then it pretty much is. I have modified my six calibration points to take into account deadtime for the GMC-800. It isn't noticeable on the everyday readings. I'll be testing response with and without those adjustments on some samples, and looking forward to seeing what the calibration point adjustment from the certification lab looks like, but I think the meter itself really does the job out of the box for the vast majority of users. It also is making full use of the range of this particular GM tube. So if you’re expecting to see something higher than 2000 uSv/h (200 mR/h), then the second less sensitive tube on the 500+ may be a better match (and really at that point you’ve already entered a radioactivity range to don’t want to be in for very long).
I haven’t seen a response that is noisey. But when display was on all the time battery life was short (day and a half). When using the dimming feature it about doubled battery life. Best approach for me was to set it to turn off display after 25 seconds. It comes right back on with a quick press of the power button so can get a reading without waiting. Really all I need when carrying it around. Otherwise this is nice portable meter.
I would like to see GQ add additional features in response to user requests, but this is a nice dosimeter and has a lot of user features that make monitoring that straight forward.
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Stargazer 40 |
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GMC-800 Concerns
