Sears Tower Model 6156 GM Meter (ca. 1955-1960)
![Sears Tower Model 6156 GM Meter (ca. 1955-1960)](../../../img/museum/survey-instruments/sears-tower-model-6156-gm-meter.jpg)
This GM survey meter was manufactured for the Sears Roebuck Company by El-Tronics Inc. of Philadelphia. A very similar instrument was sold under the El-Tronics name as the Model PR-4. The latter was described in the Atomic Energy Commission Instrument Catalog as follows: "Light weight field geiger survey meter for location of radioactive ores; provides visual and audible indication of radioactivity by flashing neon light and loud clicks in phones."
![Sears Tower Model 6156 GM Meter (ca. 1955-1960)](../../../img/museum/survey-instruments/sears-tower-model-6156-gm-meter-box.jpg)
The photo shows the original box that the instrument came in.
The GM tube is mounted inside the case at the bottom. It is covered by a thin mylar (?) window.
Detector: GM tube, 30 mg/cm2 wall
Size: ca. 4" x 7" x 1 3/4"
Weight: ca. 3 lbs.
Output: No speaker, but it has a phone jack and a small light that flashes according to the count rate
Batteries: Two 1 1/2 volt
References
- Sears Roebuck & Co. Instructions for Geiger Counter Model 6156. No date.
- Atomic Energy Commission. (El-Tronics PR-4), AEC Radiation Measuring Instruments, RIB-8 (supplement 2) July 1, 1954, page SGM-110A.