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Chapter 11: Basics of Taking Measurements
The Inspector 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 Inspector about 1-2 centimeters
from the surface while moving the unit horizontally across the survey area at a rate of 2 inches per second.
How to Perform a General Survey
A general survey would be used to find a potential source. For example, if you are looking for a potential
source in a pile of scrap, the Inspector will typically detect about 2 feet into a pile. It is easier to find a source
when the Inspector is set to Fast Response mode. However, even if the Inspector is in Auto-Averaging mode,
the audio clicks that indicate a count should be a sufficient indicator if a potential source is present. To find the
source, slowly move the Inspector in the direction of the higher readings or clicks until the potential source is
found.