• Compact Radiation Detector

Compact Radiation Detector

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The Monitor 200 measures alpha, beta, gamma, and x-rays. 

Its digital display shows readings in your choice of counts per minute (CPM), CPS, μSv/hr, mR/hr, or in accumulated counts. Now with USB and the included Observer USB Software, you can download your accumulated data from the Digilert200’s internal memory, set alarms, and calibrate your instrument!



Halogen-quenched GM tube with thin mica end window. Mica window density 1.5-2.0 mg/cm2. Effective window diameter is .360 inch. Side wall is .012 inch thick.


Operating Range

  • mR/hr - .001 (1μR) to 200 mR/hr
  • μSv/hr - .01 to 2000
  • CPM - 0 to 214,000
  • CPS - 0 to 3575
  • Total/ Timer - 1 to 9,999,000 counts


Accuracy : ±10% typical (NIST), Typically ±15% of reading.

Energy Sensitivity : 1070 CPM/mR/hr referenced to 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.
  • Detects 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.



  • Display Backlit 4-digit liquid crystal display with mode indicators. Display updates every 3 seconds.
  • Count Ligh t Red LED flashes with each count.
  • Audio Indicator Sounds with each count (can be switched off for silent operation)
  • Alarm Pulsating beeper sounds the alarm. Three separate adjustable alert levels are used for mR/hr, CPM, μSv/hr, and CPS.
  • Outputs Dual miniature jack sends counts to CMOScompatible devices, including computers, data loggers, and educational data collection systems. USB for use with Observer USB Software for PCs
  • Anti-Saturation Readout will hold at full scale in radiation fields as high as 100 times the maximum reading.
  • Power Requirements One 9-volt alkaline battery. Battery life is approx. - 2000 hours at normal background radiation levels.
  • Temperature Range -10° to +50°C (14° to 122°F)
  • Weight 217 g (7.7 oz.)
  • Size 150 x 80 x 31 mm (6.1 x 3.1 x 1.2 in.)
  • Options Xtreme Boot & Stand
  • Limited Warranty 1 year limited warranty



Utility Menu

The Utility Menu offers several options accessible by holding down the + button while turning the instrument on.

  • 3 second (fast response)
  • Switches from mR/hr and CPM to μSv/hr and CPS
  • Reset the cal factor to 100.
  • Adjust the CAL factor.
  • Reset all setting to default factory setting.