S.E. International Radiation Alert Inspector USB has built in efficiencies for common isotopes to calculate activity in Bequerels and DPM. It is optimized to detect small changes (low levels) in radiation levels and to have high sensitivity to many common radionuclides. The new back lit display shows readings in your choice of counts per minute (CPM), counts per second (CPS) uSv/hr, mR/hr, or in accumulated counts. The Inspector USB counts ionizing radiation changes, and the unit of measurement is selected and displayed using the mode switch. The display shows various indicators, based on the mode setting, the function performed, and remaining battery power. These include low battery, alert, timer, total mode calibration mode, utility menu (timer, calibration, alarm set mode), and units of measurement. Reading ranges: 0.001 (1&muR) to 100.00 mR/hr, or 0 to 350000 CPM, or 0.01 to 1000 µSv/hr, 0 to 5000 CPS, total counts 9999000 µSv/hr. Calibration: Calibrated electronically using the free Observer USB software. Accuracy: MR/hr + or - 10 percent (NIST), + or -15 percent maximum 0 to 100, µSv/hr + or - 10 percent (NIST), + or - 15 percent maximum 0.01 to 1000, CPM + or - 10 percent (NIST), + or -15 percent maximum 0 to 350000. It has a factory default calibration reset option that will automatically reset to auto averaging, mR/hr, CPM, and CAL (calibration) 100. Energy sensitivity: 3340 CPM/mR/hr, referenced to Cesium (Cs) 137. Energy sensitivity detects alpha down to 2.0 MeV. It detects beta at 0.16 MeV with typical 25 percent detection efficiency at 1 MeV. It detects gamma down to 10 keV through the end window. It detects gamma and x-rays down to 10 keV typical through the window, and 40 keV minimum through the sidewall. GM tube: A halogen-quenched, uncompensated GM tube with an effective diameter of 1.75-inches. Normal background radiation: approx 10 to 20 CPM. The meter will hold at full-scale in fields as high as 100 times the maximum reading for anti-saturation. The meter is powered by a 9-volt alkaline battery (not included).