Compact Analog Radiation Survey Meter

The Radiation Alert® Monitor 4 is a compact, analog radiation survey meter designed for dependable, general‑purpose radiation monitoring. Known for its long‑standing reliability, the Monitor 4 detects alpha, beta, gamma, and X‑ray radiation across three selectable measurement ranges, making it suitable for a wide variety of radiation safety and survey applications.

Proven Analog Performance

With decades of industry use, the Monitor 4 has earned a reputation as one of the most trusted analog radiation detectors available. Its analog response provides immediate, continuous indication of radiation levels, preferred by many professionals for real‑time situational awareness.

Simple, Ergonomic Operation

The Monitor 4 features an ergonomic, user‑friendly design that supports efficient operation in both facility and field environments. A red count indicator light flashes with each detected event, while an audible beep provides clear audible confirmation of radiation counts.

Additional convenience features include:

• Thumb‑operated battery check for quick readiness verification
• Silent operation mode for low‑noise environments

These design elements make the Monitor 4 easy to operate with minimal training.

Ideal Applications

The Radiation Alert® Monitor 4 is commonly used for:

• General radiation surveys
• Facility and laboratory monitoring
• Educational and training environments
• Routine radiation safety inspections

Specifications

Detector

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.

Audio Indicator

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

Outputs

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)

Humidity

10% to 70% Non-Condensing.

Weight

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

Size

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

Includes

Carrying Case w/ Belt Clip

Options

SI Meter Option, Observer Serial Software

Limited Warranty

1 year limited warranty