Civil Defense Geiger Counters
From Biocrawler, the free encyclopedia.
Most Civil Defense Geiger Counters were issued by the United States Civil Defense during the 1960s in the midst of the Cold War in an effort to help prepare citizens for a nuclear attack. Although referred to as geiger counters, most CD devices were radiological survey meters capable of measuring only high levels of radiation that would be present after a nuclear event.
Manufacturers
CD meters were produced by a number of different firms under contract. Victoreen, Lionel, Electro Neutronics, Nuclear Measurements, Chatham Electronics, International Pump and Machine Works, Universal Atomics, Anton Electronic Laboratories are many of the manufactures contracted. Regardless of producer, all counters exhibit the same basic characteristics, albeit with slight variations between some production runs: a yellow case with black knobs and meter bezels. All meters had a "CD" sticker on the side of the case.
Models
CD Counters came in a variety of different models, each with specific capabilities:
- CDV-700 - This is an actual geiger counter with a geiger tube. Detects beta radiation and gamma radiation with the detecting wand's beta shield open, or gammas only when the shield is closed. Used to detect low levels of radiation, but must be used in conjunction with a survey meter (below) in high-radiation areas. High-radiation fields can saturate the geiger tube, causing the meter to read a very low level of radiation (close to 0R/hr) causing the user to believe it is safe when it most definately is not! Maximum reading of 50mR/hr. In rare cases, this particular counter was modified to detect alpha radiation in addition to betas and gammas.
- CDV-715 - By far the most popular meter on the market today. This is the simplest radiological survey meter, specifically designed for high-radiation fields as geiger tubes could become saturated and read dangerously low levels of radiation. Survey meters do not read alpha or beta radiation. They work by radiation penetrating the case of the unit and the enclosed ionization chamber to produce a visible reading between .1R/hr and 500R/hr. If you can get this unit (or any other like it) to react to any source of radiation evacuate the area immediately!
- CDV-717 - Similar to the CDV-715, this unit reads from .1R/hr to 500R/hr. It is also a survey meter with an ionization chamber, however this unit's chamber is detachable for hanging outside your shelter or basement. An extension coaxial cord, included, is then run from the outdoor chamber to the indoor meter. This would allow those hiding to wait until outside radiation levels have fallen to a "safe" level before emerging. When using the extension cord, a slight delay in measurement readings occurs, however this is not really an issue as outdoor radiation levels are unlikely to change quickly.
- CDV-720 - This is a survey meter with a twist. Similar to the CDV-715, the CDV-720 is a fixed-position ionization chamber survey meter. Unlike any other survey meter, however, this unit has a movable beta shield on the bottom of the unit for detecting high levels of beta radiation. When slid to the open position, beta particles are allowed to directly penetrate the ionization chamber. With the beta shield closed, only gammas can penetrate both the shield and ionization chamber. This meter also reads from .1R/hr to 500R/hr.
