as promised i want to share some test results with real radioactive sources with you.
Before i start, one comment - I have access to radioactive sources as i am working in a radioactive laboratory of a Swiss research Institute (http://www.psi.ch) where normal radio protection rules apply. I am working in a controlled zone, have had to pass a training course and i do wear a dosimeter. Every measurement i publish here was done by myself being aware of basic radio-protection rules.
Basically i did a comparison of the readings of a V2.01 device obtained end of March from this project with a certified one available at our laboratory. It is a 6150 AD 6/H dosimeter calibrated at the accredited dosimetry calibration laboratory at PSI, Switzerland. Furthermore, i have had the opportunity to make some preliminary tests in this laboratory with the Radioactive@home device.
First of all - here a picture of the dosimeter at our laboratory:
sorry for the crappy quality, i will try to make better pictures in future.
I tested this device with two radioactive sources from our lab. One is a 373 kBq (01.03.2006) Co-60 source, the other one is 117 kBq Cs-137 of the same date. The measurement was done with both detectors directly attached to the source (not a true scientific approach). The buzzer was on.
Co-60 with readings:
Cs-137 with readings:
you see a clear difference in the values. the readings of the Radioactive@home device are about 30% below the readings of the certified dosimeter.
some more pictures of the sources:
additionally i made a test with both sources and sample of quite high doserate just to see how much the detector may stand:
you see - the device is measuring 0.5 mSv/h where it should read 1 mSv/h. Basically one can say that the device is measuring too low dose rates (Which may not automatically apply to background measurements).
The approach i have chosen is not really meaningful as the radiation field that is generated is not homogeneous if the source has direct contact to the device (The discharge tube of the 6150 device is shorter, so there are some limitation for my measurements just from geometrical considerations).
A much better approach is to generate a homogeneous radiation field from a powerful source at a certain distance. This was possible at the certified dosimeter calibration laboratory at my institute. There, they generated radiation fields between 1 and 100 µSv/h with Co-60 and Cs-137 sources of much higher activities.
The outcome of this test is: for Co-60 (mean 1200 keV gamma line) the readings of the V2.01 device where 20% below the expected value, for Cs-137 (600 keV mean) it was already 40%. The operator said that for a self-made device, this thing performs quite well (good background statistics, reasonable results for the dose rate tests).
Congratulations, Team Poland!