Calibrating BroHogan’s geiger counter kit. Default ratio is defined in Arduino sketch – 175.43 for GM tube SBM-20. Calibration source is Sr90 (BETA) from Army geiger counter control/calibration source. Result’s are compared with geiger counters: – TERRA MKS-05 Professional Black – DR-M3 (Army GC) – DR-M11B (Army GC) Conclusion: Geiger counter kit from BroHogan has very good performance and high mesuring capabilities. Device is accurate enough to be used for any purpose (measurement of background radioactivity, in the case of nuclear accident, hobby). I recommend it !!!