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 (G-M) 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 mounted beeper can be turned off for silent operation. The Monitor 4 has a one-year, limited warranty.
| 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. |
| G-M 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, sometimes called Geiger counters or G-M counters, can detect a broad range of ionizing alpha and beta particles, and gamma and x-rays that may be emitting harmful levels of radiation. Many detectors sense ionizing radiation with an enclosed Geiger-Mueller (G-M) 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.
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