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Readings
All units are calibrated at the factory using gamma radiation. The
radioactive gamma source used in the factory is Cesium-137 that
has been Beta shielded with .062" of Aluminum, and measuring
other radioisotopes (as would usually be the case) introduces
some amount of error. The error caused by this is usually very little.
Note that in the case of X-rays, the unit is very sensitive and
subsequently meter readings should be divided by about 5.
The DX-2 instruments have been calibrated in compliance with
NRC (US Nuclear Regulatory Commission) rules and regulations,
title 10, Chap. 1, Code of Federal Regulations, Part 34.25. For how
often you have to calibrate your unit, check with your local NRC.
However, recalibration is recommended after each repair or
change of the G-M tube. Since the DX-2 radiation monitor has an
oscillator, it can have minor adjustments/calibration by turning the
screw on the oscillator with a small screwdriver in the desired
direction: turning clockwise to decrease reading can be done at a
licensed place by a professional. The adjustment pot is readily
seen on the back of the DX-2.
In addition to the analog display, a special logarithmic scale has
been designed into the DX-1/DX-2. At radiation levels that are in
excess of the analog scale, the DX-1 will emit beeps at a rate that
increases as the radiation level increases above 10mR/hr.
Although this range is not as accurate as the meter, beeping will
begin approximately at 10mR/hr. A continuous beep occurs
approximately at 20mR/hr. These features greatly simplify
operation and allow reasonably quick and reasonably accurate
measurements to be made of radiation.
The analog display is not intended to indicate levels below
0.1mR/hr. However, very low level measurements can be made by
simply counting the clicks over a period of time much like taking a
person's pulse, and expressing the result as clicks (or counts) per
minute. 0.1 mR/hr on the meter corresponds to approximately 200
counts per minute (based on gamma emitting isotope).
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