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uSv is calculated using a conversion factor baked into the firmware. The conversion factor converts CPM to uSv/hr.
I don't have much additional information - the conversion factor is typically provided by the geiger tube manufacturer.

It looks like the ATtiny861A uses a slightly different pinout for HVPP. As a result, the existing sketch won't work without modification.

Did you purchase a kit? If so, email your order details to support@mightyohm.com and let's work together on getting this working for you.

Unfortunately this is not possible to do in software. You can try shielding the tube with some metal foil to decrease beta sensitivity.

The orientation of the tube definitely affects the sensitivity. It should be parallel to the source to maximize sensitivity.

flipflip -

Wow, that display is really cool! Thanks for sharing.

I'll see if I can fix the attachment settings, sorry about that!

Again, it is very hard to say because it depends on the nature of the radiation, the difficulty of interpreting the results, and what is considered "safe". It would be very difficult to use the kit safely in an area with that level of radiation. The kit is not intended to be used for this ...

The intensity of radiation measured at a distance from a radioactive source falls with the square of the distance from the source. This is called the inverse square law: https://www.nde-ed.org/GeneralResources/Formula/RTFormula/InverseSquare/InverseSquareLaw.htm A really powerful source will be meas...

That’s a difficult question to answer as it depends on the source you are trying to measure. Can you provide more details?

It will depend on the tube you decide to use. The datasheet for the SBM-20 is here:

https://www.gstube.com/data/2398/

It shows 0.014 - 144 mR/hr but I haven't verified this.

Sorry I couldn’t reply sooner. Glad you got it working. Any idea why your other usb serial adapters aren’t working?