GQ GMC-320Plus Fulfill Nuclear Radiation Detector Meter Test Equipment

This is a very good Geiger counter for the price. I've been using it for some at-home, low-budget experiments with small amounts of radioactive substances, and it has worked extremely well, with very consistent readings both when left in the same spot with background radiation and when it is placed next to a radioactive source (a sealed check source, uranium ore, a 2.33 g piece of depleted uranium metal, a thorium gas mantle, etc). Battery life is excellent.I have also had good luck with the software. The device records the number of counts for every second in its memory, which holds about two weeks of data. The software allowed me to download the data to my computer and convert it to CSV format, which can then be analyzed in Excel to see variations in natural background radiation, to determine if a very slightly radioactive source is measurably more radioactive than background, and the like.The sensitivity is a little low and quite dependent on where an object is placed relative to the narrow Geiger-Mueller tube, which is located at the bottom of the device below the buttons. I have two check sources: a sodium-22 source to check gamma sensitivity and a thallium-204 source for betas. With the beta source, I found that the plastic surrounding the GM tube prevents it from picking up the betas emitted by Tl-204 (maximum energy 764 keV; the advertised minimum for this device is 250 keV). If you open it up and put the source directly against the GM tube, it does gain the ability to detect them, although you shouldn't do this with non-sealed sources because they will contaminate the tube. With the gamma source, a 2-hour average of 6032 cpm was recorded, based on the source being placed directly against the bottom of the unit with the plastic back on. From this, I calculated an efficiency of 0.57%. This is a little low, but it still makes for a very useful device.Finally, the manufacturer runs a helpful forum where you can ask questions and try to solve issues you might have with it, and I hear their customer service is good although I've never used it myself. All in all, I'm very satisfied and the price can't be beat.edit: Got a third sealed check source: manganese-54, which emits only one gamma ray at 835 keV (99.98% of the time) and virtually nothing else. The sensitivity was only about 0.30%. I believe I overestimated Na-22 because it emits both a gamma and a positron (which produces another two gammas) on the vast majority of its decays. But even 0.3% is fine for most purposes and everything else is fantastic, so I'll keep the rating at 5 stars.

This is an amazingly feature packed little device, and very well thought out. The screen is large and clear and backlit, and is put to good use. It even has a builtin gyroscope so it can flip the screen if it is held upside down. You can data log with it, and you can even hook it up via USB to your PC. It charges via USB as well, very convenient.The included detector tube inside the unit is an M4011, not the most sensitive and it will not detect alphas. But this is a good choice for a beginner and is inexpensive and pretty durable.The GMC-320+ is reasonably hackable. I just modified mine to accept an LND-7312 which is an exceptionally sensitive alpha/beta/gamma pancake detector. If you have a known calibration source, you can calibrate the device to uSv/h.Highly recommended.

This is a great little geiger counter (nuclear radiation monitor). This does not read EMF...that is another type of monitor. The GMC-320 measures Beta, Gamma, and X-Ray radiation. The GMC-320 does not measure Alpha radiation but the GMC-600/Plus does measure Alpha radiation. The GMC-320 does not have WiFi connectivity but the GMC-320 Plus does have WiFi connectivity. I am checking the GMC-320 with several types of radiation sources such as: rocks, beads and lantern mantles. I'm comparing the readings to an old Radalert (Model 50 or 100). The lantern mantles are quite energetic. There are all kinds of display modes including graphing. The monitor can interface with a computer. The monitor includes rechargeable batteries and can be charged via USB connection. The monitor measures 3 x 5 x 1" and weighs 4.37 ounces. A great little geiger counter!

This is a nice little unit, I have had it approximately one month and have had very few issues with it.Pros:Battery life you wish your smartphone had.. I have gotten 3 days of life out of the battery with the power save disabled, speaker on and back light at its lowest setting with some power to spare.Plenty sensitive for background measurements.Logging features seem to work... I have it set for every second and get about a week of stored readings.Several display options, I usually leave it on text mode and primarily pay attention to the CPM and total count readings.Lowest price meter that offered logging capabilities I could find.Cons:The buttons are a bit difficult to push and get the unit to register them, this seemed to get better with use as the buttons seemed to need a "break in".mini-USB connection is a bit too easy to disconnect by mistake (GQ mentions what seems to be a simple fix in their forums but I have not tried it yet)Short timeouts in the menu options mean you have to be ready to push the right button at the right time.The motion detection is a little sensitive and often won't keep the backlight/speaker off when the unit is lying on its back, I'm sure some firmware tweaks could fix.Some readings:Background (Near Raleigh NC) 15-18 CPMBackground while driving through South Central VA 20-45 CPM (varied wildly)Potassium bicarbonate in plastic bag next to the GM tube: 28CPM (11 hr average)"depression glass" ash tray 29CPMLantern Mantels (old type which contain thorium) 1200-1500CPM20CPM = .1uSv/hr (based on looking at the display, I have no idea what source it was calibrated against)

Went to Japan on business right after Fukushima incident. Took it with me tested my food to make sure it wasn’t radioactive my hotel room and elsewhere. Worked well.

Works great with great battery life. It was unnerving at first because it immediately started to count, but this is normal background radiation. A bargain at this price, worth much more.