Monitor 4 and 4E Analog Survey Meters Specifications

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Detector Monitor 4: Halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick. Monitor 4EC: Halogen-quenched GM tube, energy compensated sidewall 2mm tin filter. Thin mica window 1.5-2.0 mg/cm2 thick.
Operating Range 0-.5, 0-5, 0-50 mR/hr and 0-500, 0-5,000, 0-50,000 CPM or 0-500 µSv/hr and 0-50 mR/hr.
Range Switch X1, X10, X100, Battery Check.
Accuracy ±10% of full scale (referenced to Cs-137)
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 75% typical detection efficiency.
Detects gamma and x-rays down to 10 keV typical through the window, 40 keV minimum through the sidewall of the detector.
Normal background is approximately 10-20 CPM.
Monitor 4EC Energy Sensitivity 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 (referenced to Cs-137).

Energy Response Curve
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Monitor 4 and 4EC Analog Survey Meters