FD-71 NaI(Tl) scintillation radiometer is a sensitive
simple and portable instrument. The characteristics for this radiometer are described in this paper.
The detection capability of FD-71 radiometer is 0.5—500 µRh
-1
for terrestrial gamma radiation. The differences of the readings between different instruments are generally within 5% and the differences in reproducibility and stability of different instruments are within 3% and 5%