the accumulated amount (total dose). Therefore, we categorize radiation detection
instruments as rate meters or dosimeters, depending on the information they provide.
a. The U.S. Army has recently replaced several instruments used for measuring
(1) The radiac set, AN/PDR-27 (Geiger counter), a dose rate instrument used
for measuring low intensity (zero to 500 milliroentgens per hour) gamma radiation and
detecting beta radiation, and
(2) The radiacmeter, IM-174/A, a dose rate instrument used for detecting and
measuring high level (up to 500 roentgens per hour) gamma radiation only.
b. Both the AN/PDR-27 and the IM-l74/A were replaced by the AN/VDR-2 (see
Figure 1-9). The AN/VDR-2 detects, measures and displays gamma dose rate from
background to 100 Gy/hr; detects and displays beta particle radiation from background
to 5 cGy/hr; and measures, stores, and displays accumulated dose from 0.01 uGy to
9.99 Gy. This device is autoranging (that is, the readout is digital and requires no input
from the operator to read from the lowest to highest dose/dose rate).
Figure 1-9. Radiac Set, AN/VDR-2
c. The radiacmeter, IM-93/UD (Tactical Dosimeter--0 to 600 roentgens) or
pocket dosimeter (see Figure 1-10) measures total gamma radiation dose and utilizes a
variation of the electrical collection of ions principle of operation with immediate
information capability. The U.S. Army currently has three standard pocket dosimeters
with different operating ranges: