MONITOR 4 - Analog Radiation Detector

The Monitor 4 is compact, analog radiation detector.
Manufacturer part number: MONITOR 4

The Monitor 4 is compact, analog radiation detector. A general purpose survey meter capable of detecting alpha, beta, gamma, and x-rays over 3 selectable ranges. Proven and reliable over decades of use in the industry, the Monitor 4 has evolved into one of the best analog radiation detectors of today. Simple and ergonomic , a red count light flashes and a beep sounds with each count detected. Battery check and silent operation with the flick of your thumb.

Halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick.
Effective diameter of window is 9.1 mm (.36 in.).

Operating Range

0-.5, 0-5, 0-50 mR/hr
0-500, 0-5,000, 0-50,000 CPM
or 0-5, 0-50, 0-500 μSv/hr (SI Scale Meter Option)



Range Switch

X1, X10, X100, Battery Check.

Energy Sensitivity

1000 CPM/mR/hr (Cs137).

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 and beta at 150 keV with typical 75% detection efficiency.  Detects gamma and x-rays down to 10 keV typical through the window, 40 keV minimum through the case.Monitor 4 Energy Response


Reference to Cs137
Typically ±15% from factory, ±10% with NIST Source Calibration NIST Calibration Additional


Analog Meter holds full scale in fields as high as 100X maximum reading. CPM & mR/hr scale. Optional SI Scale Meter Available

 Optional meter scales

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