Model FF-27


  • Quickly measure large, flat areas for tritium (and C-14) surface contamination
  • Sensitive Area: 100cm2 (6cm x 21.6cm)
  • Sensitivity: 100 Bq/100cm2, 35 CPS above background
  • Low gas consumption
  • Portable, lightweight design with long battery life
  • Audible and visible alarms, RS-232 data output


The Model FF-27 is an open-window gas proportional monitor for measuring tritium (and C-14) surface contamination on flat surfaces.  The FF-27 utilizes a large, rectangular windowless probe with 100cm2 sensitive area (6cm x 21.6cm) to quickly scan large areas, using poly tape to provide repeatable spacing from the surface as well smooth, scratch-free movement.  The poly tape is easily cleaned, but may also be replaced if contaminated.

P-10 counting gas is used in the FF-27.  It is non-combustible and can be used in any environment.  Two lecture cylinders for P-10 gas are included with the instrument but are shipped empty due to shipping restrictions.  P-10 gas use is minimized by careful design of the probe and by auto shut-off of gas flow when the ‘trigger’ on the probe handle is released.  Gas flow is typically set at 800 cc/min providing a total of one hour’s use for the lecture bottle size, or longer with a larger cylinder.  Typical counting efficiency is 70% 2pi of all tritium beta emissions escaping the surface.  An optional “Model H Face Plate” can be used which will help improve counting efficiency when measuring objects that aren’t completely flat, such as hands, clothing, and equipment.

Includes PRS-7 scaler/counter/analyzer, which is a digital display pulse counter that covers a 6-decade range (1-100,000 CPS or other unit of choice).  The PRS-7 is battery-powered, with an internal lithium cell and charger, and an external 12V AC power input.  The PRS-7 has a preamplifier with a built-in single-channel analyzer with two adjustable thresholds so that pulses may be selected by their pulse height and cancel out other noise.  It can also scale the counter display by a multiplier over a wide range, and the display can show both pulse rate and total pulse count, with a timer that will stop the counter after a preset interval.  Includes an adjustable high voltage power supply with a range of 200-2500 Volts, audible/visible alarms, and RS-232 data output.

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