How to Read a Radiation Detector

A radiation detector, also known as a Geiger counter, is a hand-held electronic device that measures ionizing radiation. It's self-contained, portable and battery-powered. If you've studied radiation and its effects, you can learn to use a Geiger counter with only a brief introduction. You can use your detector to read the local background radiation or see how it responds to a stronger source.

Things You'll Need

• Low-level radioactive source

Instructions

1. Take your radiation detector outdoors or to a room with no radioactive materials.

2. Turn the detector on. Select the "battery check" setting to see the battery's condition. Replace the battery if it's low.

3. Switch the detector to its most sensitive setting, and make sure the sound is on. You should hear an occasional clicking, about one per second. This is naturally-occurring background radiation from the sky, your body and minerals in the ground.

4. Note the reading on the meter. If the meter's been properly calibrated, you will be reading the background radiation in units of millirems per hour or millisieverts per hour. It should read significantly under 1 millirem per hour, or .01 millisievert per hour.

5. Bring the radiation source to within a foot of the detector. The clicking should now be very rapid, and the meter may read off the high end of the scale.

Tips & Warnings

• If your meter has a slow and fast setting, setting it to slow will average the readings. The fast setting responds more quickly to changes.

• Normal background radiation in the United States averages about 60 millirems per year. On a radiation meter scaled in millirems per hour, background radiation should read about .007. It may read somewhat higher or lower.

• Safe radiation sources can be purchased at science and educational supply stores. Note the half-life of the source, as some lose their radioactivity more quickly than others.

• Though many radiation detectors are scaled in millirems, the millisievert has replaced millirem as a unit: 100 millirem = 1 millisievert.

• Don't attempt to use strong radiation sources without proper training and safety equipment.

References

• Industrial Fire World: Counting on the Geiger Counter
• Health Physics Society: Radiation Basics