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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