Model 357RM-C14


  • Coaxial gamma compensation (2L volume) and ion trap
  • Sensitivity: 0.2 µCi/m3 or 0.01 MBq/m3
  • Range: 0.1 to 1,999.9 µCi/m3, 0.01 to 199.99 MBq/m3, DAC, and MPCa
  • Single adjustable alarm set-point
  • Audible and visual alarm indicators for signal level, low flow (optional)
  • Alpha pulse suppression, radon rejection
  • Long-term zero stable, span calibration is permanently stable due to special electrometer design


The Model 357RM-C14 is our basic, low-cost, general purpose stationary C-14 (CO2) in air monitor designed for continuous duty.  Measuring C-14 is similar to measuring tritium, as both radioisotopes are low-energy beta emitters, although C-14 is almost ten times as energetic with a beta emission of 156 keV versus 18 keV for tritium.   Suitable for 19” rack-mount or table-top use, the Model 357RM-C14 includes the essential components required for the accurate measurement of C-14 in air: dual 2L ionization chambers with coaxial gamma compensation, pump system with HEPA filter and flowmeter, alpha (radon) pulse suppression, and a single adjustable alarm set-point with audible and visible alarm.

The only maintenance required for the 357RM-C14 is periodic service of the pump and replacement of the dust filter.  The sensitivity, accuracy, and noise level of the Model 357RM is superior to competitive instrumentation by an order of magnitude.  If requested, the HTO gas ports can be installed on the compensation chamber for noble gas or other radioactive gas compensation.

The Model 357RM-C14 includes 0-10VDC analog output found on all our stationary instruments and can support one additional data output (choice of: RS-232, RS-485, 4-20mA, or Ethernet).  It has a simple alarm system consisting of a single independent signal alarm and a toggle switch with three alarm modes: on, off, and reset.  An optional low flow alarm with a front panel alarm indicator can be added.  The signal alarm activates the acoustic signal and will continue to operate until manually reset, even if the displayed signal has receded below the setpoint.  A remote alarm unit can be added that includes a latching or timing circuit to easily mute and re-set the alarm.  Relay interface connections are included on a terminal block at the rear of the enclosure.

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