The Geiger counter, invented in 1900, is an essential tool for the safe management of radioactive materials. It is robust, portable and easy to handle. As with most equipment, its best performance depends on careful use. Learn your limitations. It will not pick up some forms of radiation. It has to be directed to where the radiation is expected to be. To maintain your accurate readings and your acute sensitivity, you need periodic maintenance.
A Geiger counter consists of two main parts: physical Geiger-Müller (GM) tube and counter. The tube is sensitive to ionizing radiation. It is enclosed in a rugged metal cylinder open at one end, usually with a plastic cap. A cable connects the tube to the bar. The counter is a metal box containing the electronics, the battery, the meter and speakers. Indicates radiation as a meter line reading and audible clicks. Some have a digital account screen instead of a meter.
The counter is more sensitive to radiation entering the front, open part of the GM tube. This helps you locate unknown sources of radiation; By shaking the part of the tube around you will realize that the strongest radioactivity comes. On the other hand, if the tube is misdirected, the sources of radiation may be lost.
Geiger counters are sensitive to ionizing radiation: alpha and beta particles, X-rays, gamma rays and cosmic rays. Alpha and beta radiation are easily blocked; if they are in a closed cabinet or package, the Geiger counter will detect them badly, in any case. X-rays and gamma rays penetrate strongly and are easily detected unless shielded with lead or concrete. Infrared, ultraviolet, and neutrons are non-ionizing radiations and will not be picked up by a Geiger counter.
Most Geiger counters, to stay accurate, need to have their electronics calibrated annually. The Geiger-Muller tube itself does not need maintenance, but the circuits do. During calibration, a technician uses the Geiger counter to measure the strength of radioactive sources known accurately. She makes adjustments in the circuit until the meter readings match the intensity of the source. If a unit sees a large amount of usage and has not been calibrated for several years, it may not be accurate.
Geiger portable meters work with batteries; Many use a single 9-volt battery. If the battery power is low, the unit may be inaccurate or not work at all. Most Geiger counters have a battery test switch that will show your condition. If in doubt, replace the battery.