About Calibration and the bGeigie Nano

The bGeigie Nano is a solid-state, fully digital device. Because of its design, its performance is extremely consistent, and unlike devices with analog components which can be affected by temperature and other effects, further calibration is not expected to be necessary.

bGeigie Nano units have periodically been put through stringent calibration tests at QualTek in the US, at the Jülich Research Centre in Germany, and at the IAEA testing laboratory in Seibersdorf, Austria. In all cases the measured accuracy has been shown to be compatible with the SAFECAST specifications (Accuracy: +/- 10% typical, +/- 15% maximum ). Please note that +/- 10% is currently considered excellent performance for a Geiger counter.

Safecast is continually refining our technology and expanding our monitoring programs.  Our current quality control program and methodology typically provides minimum + and – 15% accuracy for gamma radiation from the m137 Barium daughter of Cesium 137. This is the primary source of gamma radiation from the Fukushima Daiichi accident, and we consider this level of accuracy to be sufficient for the needs of our program.

The Safecast system is designed to achieve increasing statistical accuracy as measurements are repeated with multiple units over time. This is, in fact, one of the most important innovations of the Safecast system, which was designed from the outset to take advantage of technical possibilities presented by crowdsourced activity that would otherwise only be achievable at extremely high cost. The benefits of the Safecast system, when used in the proper way, have been recognized by agencies such as the IAEA, UNSCEAR, US DOE, and experts from many leading technical institutions who have sought our advice and input.

Key components of the Nano, specifically the iRover high-voltage supply, are sourced from International Medcom, in Sebastopol Calif. Every board is tested at the factory for electronic accuracy and is guaranteed up to spec. In addition, the LND 7317 pancake GM tube used by the Nano is a very well characterized component, with well-understood performance. In the Safecast system, data is recorded and reported as raw CPM data, and conversions to uSv/hr (human doses) is done at the visualization stage.

It is important to note that unlike gamma scintillators, the Nano will also detect the beta radiation from Cesium 137 and Cesium 134.  We have protocols and data submission guidelines that allow reporting beta radiation levels to our API in appropriate ways, because we feel it can be significant for understanding overall risks. As time progresses we will continue to refine our instrumentation and databases and make continual improvements to the data and services that we provide.

Lastly, we feel it is important to point out that human error is usually a greater source of measurement inaccuracy than minor variances in hardware. Safecast has established guidelines and educational programs to guard against improper measurement, and consider radiation measurement training to be one of our most important activities.

We welcome feedback from the public on our programs.

About the Author

Azby Brown

Azby Brown is Safecast's lead researcher and primary author of the Safecast Report. A widely published authority in the fields of design, architecture, and the environment, he has lived in Japan for over 30 years, and founded the KIT Future Design Institute in 2003. He joined Safecast in mid-2011, and frequently represents the group at international expert conferences.