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FTLAB FSG-001 – A $30 Geiger Counter for Android and iOS (cnx-software.com)
51 points by zxv on July 30, 2016 | hide | past | web | favorite | 20 comments

This thing can never be "accurate". Proper instantaneous measurements for radiation require more than a good detector. The operator is part of the equation.

Say you have two pieces of fish in front of you. Answering the question "which one is more radioactive" requires more than holding a device over each for a couple minutes. You have to think of the flux, the surface area of the fish visible to the detector, the orientation of the detector, any background sources, the mass of each piece and most importantly the distance between the fish and the detector. That cannot be built into a hand-held consumer product. Absent that, these devices will only scare people.

Note the pic in the OP showing the detector plugged in via an extension cable. I'd bet that they moved it around until magically it's measurement lined up with the other device.

Also, low levels of radiation are nothing to be concerned with. The linear no-threshold model (the direct relationship between radiation and cancer) is no longer considered appropriate when discussing very low levels.

I assume it is just marketing. This is cheap chinese device. And spec says:

> Measurement error – <30% within a given deviation between

For many people even 50% error is acceptable. It is just to check if house or hotel is safe. I live at place where radon, radioactive ashes, low concentrations of uran.. are credible danger.

30% is the error rate for measuring radiation AT the detector. In doing something like comparing pieces of fish, with all the factors mentioned above, I'd expect monumentally greater error rates, of several thousand percentages... rendering the device useless.

There is plenty of evidence that the stress created by a device like this, by an obsession with infinitesimal amounts of background radiation, does far more harm. I see no net health benefit from such products.

Fyi, a 25% error rate detector can be build using a soup can and some string. (Not a joke. This thing actually works.)


Just to kind of mirror what the poster you're replying to said, it is "unlikely" you could use this to accurately detect radon. This article[0] talks about some of the difficulties you may face and how much data you'd need to collect.

Considering how inexpensive and reliable radon test kits are, it may be advisable to stick to that.

[0] http://www.azomining.com/Article.aspx?ArticleID=192

I agree with the general sentiment that we shouldn't hound on this thing for not being very accurate - professionals are using professional equipment, and this is more likely aimed at preppers.

I am surprised to see that they list the operating temperature from 10 to 40c - I wonder why it stops working outside those bounds or how off those bounds are. It would love to see someone to order a few of these and review them in all sorts of different tests.

Checking food with a gamma radiation detector is not too useful. [1][2] Some "preppers" are into this, and get excited if they count for an hour and get 20% higher than usual. They're probably seeing ordinary variation in background radiation, which varies over the course of a day.

A tester called LANFOS has been developed in Japan, to deal with possibly-contaminated food from Fukishima. It's a round pot-like device with shielding and plastic scintillation detectors into which a sample can be inserted. This has been tested against other methods and the results agree with standard laboratory tests.[3] That's a practical solution in an area where you really do have to test.

If you're worried about suddenly encountering a big gamma emitter or X-ray beam, get one of these.[4]

[1] http://www.bloomberg.com/news/articles/2011-04-12/geiger-cou... [2] https://www.princeton.edu/~ota/disk3/1979/7907/790720.PDF [3] http://www.foodqualitynews.com/R-D/Radioactive-compounds-det... [4] https://www.amazon.com/NukAlertTM-radiation-detector-keychai...

Note also the Banana Equivalent Dose https://en.wikipedia.org/wiki/Banana_equivalent_dose and the related observation by Edward Teller that due to the potassium-40 in people, sleeping with two others gave roughly the same dose rate as being on site at Three Mile Island (latter from memory)....

I'm now interested in hearing about typical sleeping arrangements in Mr Teller's day.

Crowded apartments and poverty in early 20th-century Budapest?

That's what Mr. Teller wanted you to believe

Heh, sorry about the late reply, but his experience in the short lived Hungarian Soviet Republic involved their "quartering troops" in homes/apartments like his, something that at his age and the context he found profoundly disturbing (this is from memory of the recently read and superb The Making of the Atomic Bomb by Richard Rhodes).

On the other hand, this was made as a semi-joke by him, so I'm sure it has nothing to do with his memories of events back in 1919.

I'm actually reverse engineering this and similar cheap sensors as part of creating an iOS app... I'm significantly motivated by how utterly pathetic their companion apps are.

I'm using a GQ GMC320 this week and it's app is surprisingly bad. It even uses the 16bit window sytle, which I didn't think possible.

Will you publish your reverse engineering research as open source?

There is a need to verify how good this device is. What is measurment error

Any guesses on what the sensor is in this device?

The marketing material says semiconductor sensor, which is a little vague.

Possibly one or more PIN diodes, cheap and cheerful if not particularly sensitive:


I'd love to use this as an rng.

If you're looking for some fun, you can reverse bias a zener diode and measure the noise that comes out of it. It's shot noise, and you can measure it quite easily with just some simple passives and an ADC.

Wow never thought of that, that's a good idea.

I'll give it a try.

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