Radiation Alert MONITOR4EC Energy Compensated Analog-Based Ionizing Radiation Detector

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Product Description

The Radiation Alert Monitor 4EC is a hand-held radiation detector that is used to detect potentially harmful ionizing alpha and beta particles, and gamma and x-ray radiation with an internal Geiger-Mueller (G-M) tube, and has an energy-compensated sidewall for a linear reading of gamma rays and x rays (40-100 keV). This meter has a dual-scale, analog, needle-point display of counts per minute (CPM), and milliRoentgen (mR) per hour. Three selectable operational ranges detect the four main types of ionizing radiation: alpha and beta particles, and gamma rays and x-rays. Operational ranges of X1, X10, or X100 can be adjusted when the meter face peaks at the highest mR level.

The Monitor 4EC has a red, flashing counter and a beeping noise to indicate each ionizing radiation event. It has a halogen-quenched G-M tube, and a thin, mica end window for sensing some alpha and beta ionizing radiation. It checks 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 4EC has a one-year, limited warranty.


Reading Ranges0 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).
AccuracyFactory-calibrated by pulse generator, with accuracy + or -15% of reading full-scale, relative to Cesium 137.
Energy Sensitivity1,000 CPM/mR/hr (Cs137).  The energy response for gamma and x-rays through the detector sidewall is flat within +61% or -26% over the range of 40 keV to 100 keV, and within +35% or -17% over the range of 100 keV to 1.3 MeV.
DetectionAlpha 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 through the window (non-compensated), 40keV through the sidewall. Normal background is approx. 5-20 CPM.
Sidewall DetectionEnergy-compensated sidewall with 2 mm tin filter. 40 keV minimum through the sidewall of the detector. Energy compensation is only effective through the sidewall.
Temperature Range-20 degrees to 55 degrees C (-4 degrees to 131 degrees F) and an internal detector.
G-M TubeHalogen-quenched, internal Geiger-Mueller tube. The effective diameter is 0.92 cm/0.36”.
DimensionsDimensions are 209 mm x 71 mm x 50 mm (8.2” x 2.8” x 1.9”).
Weight198.1 g (7.0 oz).
Output3.5 mm headphone jack for use with observer software (not included) and Windows-based computers.
Normal Background RadiationApproximately 5 to 20 CPM.
Battery9-V alkaline battery (not included) for approximately 2,000 hours of continuous use in a normal background.
Window ThicknessThe thin mica window is 1.5-2.0 mg/cm2 thick.

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.

What’s in the Box?

  • Monitor 4EC radiation detector
  • Carrying case with belt clip
  • Instruction manual
  • Conformite Europeene (CE) certification


Product Features

  • 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
  • Energy-compensated sidewall provides more linear readings of gamma rays and x rays (above 40keV) than the Monitor 4 model