About systematic errors
Systematic errors describe errors in the output readings of a measurement system which are consistently on one side of the correct reading, i.e. either all the errors are positive or they are all negative. Two major sources of systematic errors are system disturbance during measurement and the effect of modifying inputs. Other sources of systematic error include bent meter needles, the use of un-calibrated instruments, poor cabling practices and the generation of thermal e.m.f.s. Even when systematic errors due to the above factors have been reduced or eliminated, some errors remain which are inherent in the manufacture of an instrument. These are quantified by the accuracy figure quoted in the published specifications contained in the instrument data sheet.
Systematic errors in the output of many instruments are due to factors inherent in the manufacture of the instrument arising out of tolerances in the components of the instrument. They can also arise from wear in the instrument's components over a period of time. In other cases, systematic errors are introduced either by the effect of environmental disturbances or through the disturbance of the measured system by the act of measurement. These various sources of systematic error, and the ways in which the magnitude of the errors can be reduced.