Mini-Instruments 900 Geiger Counter. Typical Applications: Contamination control/general radiation detection. Meter scale: 0 – 500 cps. Includes halogen-tempered G-M tube that is compensated to give a useful response of 45 keV to 1.5 MeV and above. Radiation Detected: Gamma and X-rays only. The built-in speaker provides an audible feedback of the radiation intensity. An alarm can be set to go off at any level on the scale. 6 cell battery. Dimensions: 180*110*165mm. It is not recommended for monitoring X-radiation from devices operating below 75 kVp.