About Measurement System Errors
About errors in measurement system
It is extremely important in any measurement system to reduce errors
in instrument output readings to the minimum possible level and to
quantify the maximum error which may exist in any output reading. This
requires a detailed analysis of the sources of error which exist in
the system as a prerequisite in this process of reducing the total
measurement error level. These errors in measurement data can be
divided into two groups, known as systematic errors and random errors.
Finally, a word must be said about the distinction between systematic
and random errors. Error sources in the measurement system must be
examined carefully to determine what type of error is present,
systematic or random, and to apply the appropriate treatment. In the
case of manual data measurements, a human observer may make a
different observation at each attempt, but it is often reasonable to
assume that the errors are random and that the mean of these readings
is likely to be close to the correct value. However, this is only true
as long as the human observer is not introducing a systematic
parallax-induced error as well by persistently reading the position of
a needle against the scale of an analog meter from the same side
rather than from directly above. In that case, correction would have
to be made for this systematic error (bias) in the measurements before
statistical techniques were applied to reduce the effect of random
errors.
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