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Monitor 4 Handheld Radiation Alert® Detector

Model #: M4

Condition: New

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Product 17 of 17

The M4 Handheld Radiation Alert® Detector senses ionizing radiation by means of a GM (Geiger ) tube with a thin mica window. The tube is enclosed inside the instrument. When a ray or particle of ionizing radiation enters or passes through the tube, it is sensed electronically and displayed by a red count light. When the switch is in the AUDIO position, the instrument will also beep with each radiation event. About 5 to 25 counts at random intervals depending on your location and altitude) can be expected every minute from naturally occurring background radiation.

The M4 is a compact, general purpose survey meter capable of detecting alpha, beta, gamma, and x-rays over 3 selectable ranges. A red count light flashes and a beep sounds with each event detected.


  • Visual and audio indication
  • Geiger Mueller tube
  • Battery operated
  • Detects radiation over three selectable ranges
  • Detects four different types of radiation:
    • X-ray
    • alpha
    • beta
    • gamma


  • Detector: Halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick
  • Display: analog meter holds full scale in fields as high as 100X maximum reading
  • Monitor 4 Energy Sensitivity:
    • Detects alpha down to 2.5 MeV; typical detection efficiency at 3.6 MeV is greater than 80%
    • Detects beta at 50 keV with typical 35% detection efficiency
    • Detects beta at 150 keV with typica 75% detection efficiency
    • Detects gamma and x-rays down to 10 keV typical through the window, 40 keV minimum through the case. (GRAPH 1)
    • Normal background is 5-20 CPM
  • Gamma sensitivity: 1000 CPM/mR/hr (referenced to Cs-137)

  • Operating ranges:
    • 0 to 0.5; 0 to 5; 0 to 50 mR/hr
    • 0 to 500; 0 to 5,000; 0 to 50,000 CPM
    • 0 to 500 µSv/hr; 0 to 50 mR/hr
  • Range Switch: X1, X10, X100 and Battery Check
  • Accuracy: typically ±15% of reading (referenced to Cs-137)
  • Audio: internally mounted beeper (can be turned off for silent operation)
  • Power requirements: 9-volt alkaline battery
  • Battery life: up to 2,000 hrs at normal background
  • Temperature range: -4° F to 131° F (-20° C to 55° C)
  • Weight: 7.9 oz (223.9 grams) without battery
  • Operating Voltage :7 to 11vDC. (high and low voltage is fully regulated)
  • Outputs: 3.5mm headphone jack with pulse out
  • Size: 8.25" x 2.75" x 1.875" (210 x 70 x 48mm)

Supplied with:

  • Carrying Case
  • 1 year limited manufacturers warranty
Product 17 of 17
Manufacturer Info