IM-174/PD Ion Chamber Survey Meters (ca. 1980s)

The IM-174 is a small high range survey meter employing an ionization chamber. Oddly enough, the IM-174 employs two logarithmic scales: the standard scale is 1 to 500 rad/hr, and a second scale, 0.1 to 10 rad/hr, which is activated when the “Check” switch is depressed.  The models 174A and 174B (photos below left) only employ a single scale: 1 to 500 rad/hr. The earliest reference I have for the IM-174 is the 1966 version of the List of Military and Civil Defense Radiac Devices while the earliest reference for the IM-174A and 174B is the 1987 version of the list.

IM-174A/PD (above)


IM-174A/PD (above)

IM-174B/PD (above)

Range:  1 – 500 rad/hr

Size: ca. 6 ½ ” x  4 1/2” x  4 1/2”

Battery: one 1 1/2 volt D cell

Weight: 3.75 pounds

Manufacturers: Landsverk (model IM-174), Jordan (model IM-174), Canadian Admiral (models IM-174A, B), Nucor (models IM-174A, B). The manufacturer of this particular example is not indicated.

This particular unit has an Army calibration sticker on it dated August 1990.

Donated by Steven Buxton

The IM-174A and 174B have two controls. One is an "OFF" - "SET" knob used to turn the instrument on and off and to zero the meter. The other control is a lever switch used to check the battery condition and to activate the zero adjust function.


Defense Atomic Support Agency, List of Military and Civil Defense Radiac Devices. DASA 1243 revised, 1966.

Naval Electronic Systems Command List of Radiacs in the Navy Program P-9670-1, February 1975.

Defense Nuclear Agency List of Military and Civil Defense Radiac Devices HQDNA (AR) 3M Revised, August 1987.

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Last updated: 05/10/11
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