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 GQ Geiger Muller Counter
 CALIBRATION

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T O P I C    R E V I E W
scottnokes Posted - 03/14/2017 : 08:33:49
Hi everyone
I have just purchased the gq300e+ and will be using it primarily on radioactive minerals like uranium ore and associated minerals and testing things like uranium glass, fiestaware and depression glass etc.
Will the factory calibration be good enough for this use or should I use another setting. Also, my CDV-700 needs calibrating, can I calibrate to this one using the same sample?
thanks
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Distelzombie Posted - 03/20/2017 : 07:15:16
GQ devices are not individually calibrated. Also, you dont seem to have understood what i was talking about: You dont need a cesium testsource and you would not want it.

What do you want to do with your gmc anyway? If you are just using it on your minerals you dont really need an accurate dosage reading. If you lock them away in your lead bunker radiation doesnt really should be of care for you. Especially since you have activity certifcates.
scottnokes Posted - 03/18/2017 : 06:35:14
Hi there
thanks for your reply. I don't have a Cesium 137 NIST test source to calibrate. My minerals came with a certificate of measured radioactivity. My Sklodowskite says 1660cpm, Its fro Minerological research company. They use a CDV700 to measure and when I asked them when theirs was calibrated they wont tell me so I don't know how accurate their readings are.
Would I be ok to use the factory setting of the gq300 to test my collection and calibrate my CDV700 to it. Theres seems to be about 1000cpm difference between the two, with the CDV reading about 1000cpm lower.
Do you know does GQ use NIST Cesiium137 to set the calibration for the factory setting?
Distelzombie Posted - 03/16/2017 : 06:29:10
Using the same sample? Yes, if it is a sample of known intensity you can calibrate any device to it correctly.
As you've probably already know, judging by your question, a calibration is only correct for the material it is calibrated on. Due to different energy released in the radioactive decay of different ions, the total dose you recieve is not equal even if counts are.
Usually all geiger müller counters for the general public are calibrated to cesium137 because I dont know right now..
Take a look in here for further explanation: h**p://www.ntanet.net/how-do-geiger-counters-work

Cesium137 decays with beta radiation at a level of 1.176 MeV.
Uranium238 however is a alpha radiator with 4.267 MeV and 49.5 keV gamma. All GQ geiger counter are not able to measre alpha radiation. They can measure beta, gamma and xray. What the device registers in case of uranium235 is bremsstrahlung, the little bit of gamma and radiation of the isotopes from the decay chain. (The beta radiator of the decay chain isotopes exist not very long: thorium234 for 24 days and proactinium234 for 7h. Everthing else is alpha until uranium234 which will last for ever again like 238) These chain isotopes make only about 1% of it, but most of the radiation of the .
Therefore i guess you have to calibrate it according to 49.5 keV gamma and about 2.2 MeV beta (Proactinium234), while keeping bremsstrahlung in mind.

Its not easy I guess.. I would take 2.268205 MeV (protactinium234), the factory settings for 1.176 MeV and calculate the new values then say its good.

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