The M4 and M4EC are both compact, ergonomic, general-purpose survey meters used to detect alpha, beta, gamma, and x-rays over three selectable ranges. Both models have a red count light that flashes and a beep that sounds with each event detected. The M4EC offers a more linear reading for gamma and x-rays (above 40 keV).

The detector for the M4 is a halogen-quenched uncompensated GM tube with a thin mica window 1.5-2.0 mg/cm2 thick, while the M4EC has a halogen-quenched GM tube with an energy-compensated sidewall 2mm tin filter and a thin mica window 1.5-2.0 mg/cm2 thick.

The energy sensitivity of both models is 1000 CPM/mR/hr (Cs137), and the M4EC has a flat energy response for gamma and x-rays through the detector sidewall 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.

The operating range of both models is 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). The accuracy is typically ±15% of reading (Cs137). The display is an analog meter that holds full scale in fields as high as 100X maximum reading, with a CPM and mR/hr scale. An optional SI Scale Meter is available.

These survey meters are commonly used for personal protection, general surveying, checking industrial gauges (such as moisture, density, or level gauges containing Cesium-137), and locating sources.