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The problem says that an ammeter has a 30 mA upper measurement limit and its accuracy class is 2%.

For the relative measurement error when measuring 22 mA, I found it is2,7%. I used the formula h(%) = hop*30/22, but for the range of uncertainty I'm not sure if I can use H = [h(%)/100]*22 because the word "range" makes me confused.

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    \$\begingroup\$ The range probably refers to something like 21.6 to 22.4 if you have 3 full digits. Errors are not always symmetrical. That does not help with your confusion: you have to ask yourself if the 2% is to be applied on the full range or on the measured value? The range that I provided above is the range if 2% is a relative error, but a Class 2% seems to imply an absolute error equal to 2% of the full scale. \$\endgroup\$
    – le_top
    Commented Dec 13, 2021 at 16:02

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Accuracy class of 2% means that the reading is within +/-2% of the full-scale (aka range) (30mA) which is +/-0.6mA (measured under some specified range of conditions such as ambient temperature).

So you can calculate what percentage that is of any reading.

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