Some of the sources of error in weighing are:
Buoyancy – Objects in air develop a buoyancy force that is directly proportional to the volume of air displaced. The difference in density of air due to barometric pressure and temperature creates errors.
Error in mass of reference weight
Air gusts, even small ones, which push the scale up or down
Friction in the moving components that causes the scale to reach equilibrium at a different configuration than a frictionless equilibrium should occur.
Settling airborne dust contributing to the weight
Mis-calibration over time, due to drift in the circuit's accuracy, or temperature change
Mis-aligned mechanical components due to thermal expansion or contraction of components
Magnetic fields acting on ferrous components
Forces from electrostatic fields, for example, from feet shuffled on carpets on a dry day
Chemical reactivity between air and the substance being weighed (or the balance itself, in the form of corrosion)
Condensation of atmospheric water on cold items
Evaporation of water from wet items
Convection of air from hot or cold items
Gravitational differences for a scale which measures force, but not for a balance.[11]
Vibration and seismic disturbances
