Model RS400


  • Highly sensitive portable tritium air monitor
  • Includes RS-232 data output
  • Cruciform gamma compensation (400cc volume) with virtually no offset in fields up to 10 mR/h
  • Sensitivity: 2 µCi/m3, 0.1 MBq/m3
  • Range: 1 to 19,999 µCi/m3 or 0.1 to 1,999.9 MBq/m3 (DAC, MPCa, and µSv/h also available)
  • Rapid warm-up and response time of less than 30 seconds
  • Audible and visual alarm indicators for low flow, low battery, and signal level
  • High voltage power supply malfunction alarm
  • Alpha pulse suppression, radon rejection
  • No long-term drift, no manual zero adjustments
  • Offset potentiometer control included
  • CE Marked


The Model RS400 is a high-performance lightweight portable tritium in air monitor.  Includes four 200cc ion chambers arranged in a cruciform geometry which provides nearly perfect gamma compensation regardless of photon energy, flux gradient, or flux direction.  Two ion chambers are used for measurement (400cc total) and two for gamma compensation (400cc total).  The Model RS400 is the same as the Model 400SBDyC but includes RS-232 data output.  The RS400 has a fast response time of less than 30 seconds and can accurately detect tritium down to a sensitivity of 2 µCi/m3 or 0.1 MBq/m3.

Power is supplied by a pair of “D” size batteries in your choice of alkaline or NiMH rechargeable.  Onset of the battery depletion is signaled by illumination of an LED located next to the meter face.  This same LED will also signal red when there is a malfunction with the high voltage power supply.  A nine-position alarm level stepped attenuator, adjustable over partial scale (2 to 1,000 µCi/m3) is located on the front panel.  A steady tone is emitted by an acoustic signaler if the measurement exceeds the alarm set-point (illuminates red LED), or if the sample airflow has been interrupted and is too low (illuminates yellow LED).  The alarms are non-latching.

Zero adjustment is unnecessary, the electrometer is completely temperature stable and shows zero drift from 0° C to 50° C due to special design and careful selection of an ultra-high impedance semiconductor with low internal current leakage and long-term DC stability.  The RS400 can reliably measure currents as low as 10-16 amperes and the span calibration is permanently stable.  The ionization chamber polarizing voltage is supplied by an electronic low-noise regulated dual high-voltage power supply (±80VDC).  The RS400 includes proprietary radon recognition and elimination circuitry to provide accurate, fast, and drift-free measurement.

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