Monitor 4

Measures alpha, beta, gamma and x-radiation over 3 selectable ranges.

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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.

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


Pocket-sized monitor with meter, LED count light, and beeper

  • Monitors alpha, beta, gamma, and x-ray radiation
  • Dual-scale analog meter (CPM and mR/hr)
  • Operating range: 0-50 mR/hr, 0-50,000 cpm
  • Multiplier selections: x1, x10, x100
  • Red LED flashes with counts
  • Audible beep indicates rising radiation level
  • Operates up to 2,000 hours on 9V battery
  • Weighs less than 9 ounces (including battery)


  • Detector: Halogen-quenched uncompensated GM tube with thin mica window 1.5-2.0 mg/cm2 thick
  • 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% efficiency
    – Detects beta at 150 keV with typical 75% efficiency
    – Detects gamma and x-rays down to 10 keV typical through the end window, 40 keV minimum through the case
  • Accuracy: ±15% of full scale (referenced to Cs-137)
  • Visual Indicators: .875″ x 1.75″ (2 x 4 cm) dual scale analog meter, marked 0-500 cpm and 0-0.5 mR/hr; LED count light
  • Audio Indicator: Internally mounted beeper (can be switched off for silent operation)
  • Range Switch: x1, x10, x100, battery check
  • Ranges: 0-500, 0-5,000, 0-50,000 cpm and 0-0.5, 0-5, 0-50 mR/hr
  • Current Drain: Typically 190µA at background radiation levels
  • Operating Voltage Range: 7-11 Volts DC
  • Voltage Regulation: High and low voltage fully regulated
  • Power Requirement: One 9-volt alkaline battery, NEDA #1604A, or equivalent
  • Battery Life: Up to 2,000 hours at normal background radiation levels
  • Temperature Range: -4°F to +131°F (-20°C to 55°C)
  • Dimensions: 8.25″ x 2.75″ x 1.87″ (210 x 70 x 48 cm)
  • Weight: 9.7 oz (.28 kg) including battery, 7.2 oz (.21 kg) without battery

Item Number

078-400 Survey Meter, Monitor 4