You may wonder what the difference between a measuring range and a display range may be. In fact, the
answer to that question may depend on national regulations. We shall give you some ideas about German
regulations dividing a simple range into a »display range« and a »measuring range«. Note, however, that
regulations in your country may be different.
According to German regulations, a measuring range is that portion of the display range meeting certain
accuracy requirements. You may regard the measuring range as the »useful« part of the display range. For
example, the error of a radiation meter must not exceed 20%. This has a simple consequence for digital
ranges. With a digital range, there is always an uncertainty of ±1 in the least significant digit. If that
uncertainty shall not make more than 20%, the measured value must amount to »5« or more in the last
digit. For example, if a display range starts at 0.00, the measuring range cannot start below 0.05. As
another example, fluctuation (standard deviation) of dose rate indication must not exceed a certain limit.
Usually such requirements are more difficult to fulfil at low dose (rate) values than at high ones.
Therefore, in most cases the beginning of a measuring range will be above the beginning of the display
range, whereas the ends of measuring and display range are usually equal.
Dose Rate Measuring Ranges
The maximum standard deviation determines the beginning of the dose rate measuring range. The
measuring ranges shown in the table below comply with the requirement, that the relative standard
deviation must not exceed 5% at dose rates above 20 µSv/h, and must not exceed 15% at dose rates
below 20 µSv/h. The end of the dose rate measuring range is equal to the end of the corresponding digital
6150AD1/3/5 internal tube
6150AD2/4/6 internal tube
The dose rate measuring ranges of the probes are valid regardless of the 6150AD model they are used
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