Nuclear Research Corporation SM-5A Survey Meter

aka Federal Civil Defense Administration Item Number CD-V-700

Size of unit: 4 3/4" High x 5" Wide x 9" Long / Weight 6 pounds. The drawing dates in the manual puts this unit as being manufactured in about 1954.

This unit measures gamma radiation up to 50 milliroentgens per hour over three scales. It uses a Geiger-Mueller tube to detect moderate and high energy beta radiation, and gamma radiation down to low energies. Unlike later versions of the CDV-700, this model uses a standard 1/4" jack to plug in the headset.

This instrument uses the following batteries: 1 each - Radio "B" battery at 67 1/2 Volts 2 each - Miniature Radio "B" batteries at 22 1/2 Volts and a mercury cell battery pack.

Probe / Geiger-Mueller tube: CK1021 by Raytheon. This is a much larger tube at 5 inches in length than the later 6993 series (at 3 3/4") used in the CDV-700 models. This survey meter will also take the Raytheon CK 1043 GM tube. Overall length of this probe is 8 inches. The Raytheon CK 1021 / CK 1043 probes were rated at 500 hours of use.