Choosing a Survey Meter

Generally, thin window Geiger-Mueller (GM) probes are best suited to detect beta radiation with energies above 70 keV while sodium iodide (NaI) scintillators are best for gamma radiation. 

For campus laboratories, the Ludlum Model 3 survey instrument is recommended. The Model 3 has the following detectors available:

If you are using P-32, Ca-45, Cl-36, C-14 or S-35 use the Ludlum Model 3 Survey Meter with Model 44-9 "Pancake" GM Probe. This instrument has a flat detector (1.75" in diameter) at the end of a handle. This style probe is comfortable to handle and is best suited for surveying large areas, such as floors, hoods and bench tops.

If you are using I-125 or other nuclides with gamma energies between 10 to 40 keV, use the Ludlum Model 3 survey meter with Model 44-3 "Low Energy Gamma" Sodium Iodide (NaI) detector.

If your are using Cr-51, I-131, Co-57 or other nuclides with gamma energies above 40 keV, use the Ludlum Model 3 survey meter with Model 44-2 "High Energy Gamma" NaI detector.