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Handheld Survey Meters : Ludlum Energy Compensation Filters

Flattens the energy response of GM detectors to facilitate measuring either Exposure or Ambient Equivalent Dose

The Ludlum Energy Compensation Filters flatten the energy response on the GM detectors such as on the Model 44-9 Pancake Detector or the Model 26 Frisker to facilitate measuring either Exposure or Ambient Equivalent Dose.

One filter is formulated specifically for measuring Exposure (Roentgen); the other for use in measuring Ambient Equivalent Dose (Sievert).

As most know, the venerable GM pancake has a significant overresponse at lower energies between approximately 20 to 160 keV (see red line on graph opposite). Any exposure or dose measurements taken with an unfiltered GM pancake detector would thus have unacceptable errors at these lower energies.

The filters developed by Ludlum flatten the response to within ±20% referenced to 137Cs (662 keV) over an energy range of 33 keV to 1.2 MeV for Exposure and down to 20 keV for Ambient Dose Equivalent. These filters fit the newer Model 44-9 and Model 26 Series of detectors.

Both filters simply snap on across the face of the probe whenever these type of measurements are desired. The filters are then again easily removed to continue on with measuring contamination (cpm or Bq). The small hole added to the tab of the filter provides a means to secure it to the instrument preventing loss or misplacement of the filter.

Filters can be purchased separately or together with a new probe. The Dose filter supplies a filter while the Exposure filter comes in a kit that provides the filter plus a replacement detector protective screen that can easily be changed out.


Ludlum Energy Compensation Filters Printable Info Sheet (PDF)