Monitor4 Handheld
Radiation Alert® Detector

Same Monitor 4. New ergonomic design. The M4 is compact, general purpose survey meters 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.





Monitor 4: Halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick. 

Analog Meter holds full scale in fields as high as 100X maximum reading. CPM/mR/hr scale default. Optional SI Meter Scale option available upon request. 

Energy Sensitivity
M4: Detects alpha down to 2.5 MeV; typical detection efficiency at 3.6 MeV > 80%. Detects beta at 50 keV with 35% efficiency. Detects beta at 150 keV with 75% efficiency. Detects gamma and x-rays down to 10 keV through the window, 40 keV minimum through the sidewall. Normal background is approximately 10-20 CPM.


Gamma Sensitivity:

  • 1000 CPM/mR/hr (referenced to Cs-137)

  • Energy Sensitivity for the 4EC is the Same as Monitor 4 except 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.



Operating Range

  • 0-.5, 0-5, 0-50 mR/hr 

  • 0-500, 0-5,000, 0-50,000 CPM or 0-500 µSv/hr 

  • 0-50 mR/hr.

  • Range Switch

  • X1, X10, X100, Battery Check.

  • Accuracy

  • Typically ±15% of reading(referenced to Cs-137)



Internally mounted beeper (can be turned off for silent operation).

Power Requirements

9-volt alkaline battery up to 2,000 hrs at normal background

Temperature Range

-20° C to 55° C (-4° F to 131° F)


M4: 223.9 grams (7.9 oz) without battery

3.5 mm headphone jack with pulse out.


210 x 70 x 48 mm (8.25 x 2.75 x 1.875 in.)

Carrying Case w/ Belt Clip

Observer Software, SI Meter Option, Mini-USB Option (Available Upon Request. USB Cable included.)


1-year limited warranty


510 Lake Street

PO Box 67 
Cascade, WI 53011

P: (920) 523-6053

M: (920) 912-5763 

This site was designed with the
website builder. Create your website today.
Start Now