Sources of Systematic Uncertainty
In determining the magnitude of Sources of Systematic Uncertainty, the contributions due to (a) measuring instrument (b) operating conditions and (c) inherent characteristic of the instrument under test are taken into consideration. Some common types of systematic uncertainties encountered in mechanical measurements may be listed as follows:
Uncertainty as reported in the calibration certificate of the standard and the instrument used.
Uncertainty due to the interpolation between the calibration points of the standards used in the measurement.
Uncertainty due to the change in environmental conditions.
Uncertainty due to lack of ability to reset, detect and repeat of the instrument under test.
Uncertainty due to the values taken of some physical constants or properties of the materials used in the measurement process. For example, uncertainty in the values of density of water, acceleration due to gravity, coefficients of linear expansion, temperature, pressure and relative humidity, etc.
It is assumed that the variable of systematic uncertainty follows rectangular distribution, giving the variance as one third of the square of its semi-range and infinite degrees of freedom.
Source : measurement uncertainty
