Wallac Oy RDM Personnel Monitor (early 1960s)

This personnel monitor was manufactured by Wallac Oy of Finland and sold in the U.S. by the Gelman Instrument Company.  A 1961 Gelman advertisement refers to this particular device as a "Sparrow Radiation Alarm." The name probably derives from the "chirps" that indicate the intensity of the radiation.  The detector is a miniature GM tube and the only control is an On/Off switch (upper left corner). The count rate is indicated audibly through a small speaker (upper right corner) and visibly via a small flashing light (upper center). Unfortunately, the pocket clip is missing in this particular example.

The Gelman advertisement reads: "Sparrow Radiation Alarms provide a safeguard no other device can offer. Workers are instantly warned of danger . . . Radiation accidents are impossible to predict! Don't wait - act now about personal protection."


Case:  ca. 2  x  5" x  7/8" 

Weight: 5 oz.

Batteries: two 1.5 volt mercury penlights


Donated by John Taschner


Advertisement, Nucleonics November 1961, page 233.

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Last updated: 05/10/11
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