• Radiation detector used to check levels of potentially harmful ionizing particles and rays in the environment and in objects such as particle accelerators, x-ray shielding, and industrial gauges.
• Detects ionizing radiation types such as alpha and beta particles, and gamma rays and x-rays.
• Dual-scale analog meter with needle-point display of counts per minute (CPM) and milliRoentgen (mR) per hour.
• Three selectable operation ranges of X1, X10, and X100 for adjustment when peak mR levels are met.
• Red, flashing counter and a beeping noise indicate each ionizing radiation increase event.

The Radiation Alert Monitor 4 is a hand-held radiation detector with an analog display over three selectable operational ranges for detecting potentially harmful ionizing alpha and beta particles, and gamma and x-ray radiation. This meter has a dual-scale, analog, needle-point display of counts per minute (CPM), and milliRoentgen (mR) per hour. It detects the four main types of ionizing radiation: alpha and beta particles, and gamma rays and x-rays. It has three selectable operational ranges (X1, X10, or X100) to be adjusted when the meter face peaks at the highest mR level. The Monitor 4 has a red, flashing counter and a beeping noise to indicate each ionizing radiation event. It has a halogen-quenched Geiger Mueller (GM) tube with a thin, mica end window for sensing ionizing radiation. It is used to check radiation levels in the environment and objects, such as particle accelerators, x-ray shielding, and industrial gauges. An audio indicator with an internally ed beeper can be turned off for silent operation. The Monitor 4 cannot be returned. Specifications -------------- Reading Ranges 0 to 0.5, 0 to 5, or 0 to 50 milliRoentgen (mR) per hour, or 0 to 500, 0 to 5,000, or 0 to 50,000 cycles per minute (CPM). Accuracy Factory-calibrated by pulse generator, with accuracy + or -15% of reading full-scale, relative to Cesium 137. Energy Sensitivity 1,000 CPM/mR/hr (Cs137). Detection Alpha down to 2.5 mega (million) electron volts (MeV), with typical detection efficiency at 3.6 MeV at greater than 80%. Beta at 50 kilo (thousand) electron volts (keV) with typical 35% detection efficiency. Beta at 150 kilo (thousand) electron volts (keV) with typical 75% detection efficiency. Gamma and x-rays down to 10 keV typical. Temperature Range -20 degrees to 55 degrees C (-4 degrees to 131 degrees F) and an internal detector. GM Detector Halogen-quenched with window thickness of 1.5 to 2.0 mg/cm2. The effective diameter is 0.92 cm/0.36”. Dimensions Dimensions are 209 mm x 71 mm x 50 mm (8.2” x 2.8” x 1.9”). Weight 178 g (6.3 oz). Output 3.5 mm headphone jack for use with observer software (not included) and Windows-based computers. Normal Background Radiation Approximately 5 to 20 CPM. Battery 9-V alkaline battery (not included) for approximately 2,000 hours of continuous use in a normal background. Radiation detectors can detect a broad range of ionizing alpha and beta particles, and gamma and x-rays that may be emitting harmful levels of radiation. They sense ionizing radiation with an enclosed Geiger Mueller (GM) tube to count radiation particles or rays. Alpha and beta particles are measured in counts per minute (CPM) or counts per second (CPS). Gamma rays and x-rays are measured in milliRoentgens (mR) per hour, microSieverts (μSv) per hour, or milliSieverts (mSv) per hour. Alpha particles are positively charged and heavier than beta particles, and have a limited range of approximately 3 to 5 centimeters by air. Alpha particles can be shielded by objects such as paper and unopened skin. High-energy beta particles are electrons, heavier than gamma rays, and can take either a positive or negative charge. Beta particles can be shielded by aluminum or wood. High-frequency (short wavelength) gamma rays are the strongest and lightest rays. Gamma rays are more penetrating than alpha and beta particles. They can be shielded by dense materials such as lead, and large masses of concrete, hardened steel, or water. X-rays are man-made gamma rays, and have essentially the same properties and function. Radiation detectors commonly have either an analog or a digital display. Analog radiation detectors output with a needle-point scale, and digital units generate a numerical LCD digit display. Radiation detectors are commonly used by hobbyists for safety detection and rock inspection, and professionals in the in the nuclear, medical, mining, instructional, and research industries. SE International manufactures radiation detection products and accessories under the Radiation Alert brand. The company was founded in 1979 and is headquartered in Summertown, TN. What’s in the Box? * Monitor 4 radiation detector * Carrying case with belt clip * Instruction manual * Conformite Europeene (CE) certification