Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4
Monitor 4

The Radiation Alert® Monitor 4 is a compact, analog radiation detector designed for versatility and reliability. This general-purpose survey meter can detect alpha, beta, gamma, and X-ray radiation across three selectable ranges. With decades of proven performance in the industry, the Monitor 4 has become one of the leading analog radiation detectors available today. Its simple, ergonomic design features a red count light that flashes and an audible beep for each detected count. A quick flick of your thumb allows for an easy battery check and silent operation.

Applications & Uses: Checking industrial gauges, such as moisture, density, or level gauges containing Cesium-137, Locating Sources, Personal protection, General surveying

Analog Radiation Detector Comparison | Contact For Pricing and Availability



radiation_icon_bllack alpha_icon_black beta_icon_black gamma_icon_black x-ray_icon_black

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
Audio Indicator

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


3.5 mm jack with pulse out.

Power Requirements

9-volt alkaline battery (included). Approx. 2,000 hrs. at normal background

Temperature Range

-10° to +50°C (14° to 122°F)


10% to 70% Non-Condensing.


M4: 200 g (7.1 oz) M4EC: 224 g (7.9 oz)


209 x 71 x 50 mm (8.2 x 2.8 x 1.9 in.)


Carrying Case w/ Belt Clip


SI Meter Option, Observer Serial Software

Limited Warranty

1 year limited warranty

Included With Monitor 4

Carrying Case