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Chapter 7: Taking Measurements
The Radiation Alert® Frisker will not detect neutron, microwave, RF (radio frequency), laser, infrared,
or ultraviolet radiation. All of our instruments are most accurate for Cesium-137 and isotopes of similar
energies. Some isotopes detected relatively well by most Geiger counters are Cobalt-60, Technicium-99M,
Phosphorous-32, Strontium-90, and many forms of Radium, Plutonium, Uranium, and Thorium.
Some forms of radiation are very difficult or impossible for a Geiger tube to detect. Tritium, for example, is
a by-product of a nuclear reactor and is used in research. The beta emissions from Tritium are so weak that
there are very few instruments that are capable of detecting it. More sophisticated equipment is needed for
the measurement of environmental samples, such as radioactivity in milk, produce, soil, etc., unless you are
looking for gross contamination.
The radiation from some isotopes can cause a Geiger tube to overexcite and indicate a higher level of radiation
than is actually present. Americium 241 is an example of this phenomenon. Americium 241 is used in some
smoke detectors and many different types of industrial density and flow meters.
Unless you know exactly what you are measuring and understand the limitations of detection instruments,
it is possible to draw misleading conclusions from your readings. We design our instruments to detect the
broadest range of ionizing radiation possible and still be affordable. The full spectrum of ionizing radiation
cannot be measured by one single instrument. Everyone agrees that radioactive materials can be dangerous.
We encourage you to seek out other sources of information.
How to Detect Background Radiation
To see what the background radiation is in your area, simply turn the instrument on and, after the 30 second
start up beep, the general background radiation will be displayed.
How To Survey a Surface
When surveying a surface, such as a counter top, you will need to hold the Radiation Alert® Frisker about 1-2
centimeters from the surface while moving the unit horizontally across the survey area at a rate of 50 cm per
second.
How to Perform a General Survey
A general survey may be used to find a potential source. For example, if you are looking for a potential source
in a pile of scrap, the Radiation Alert® Frisker will typically detect about 2 feet into a pile. To find the source,
slowly move the Radiation Alert® Frisker in the direction of the higher readings or clicks until the potential
source is found.6
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