The accuracy of an analytical balance may be sensitive to a range of handling and environmental factors.
Handling:
(1) physical movement of the scale after calibration
(2) deterioration (corrosion, etc) of weights or calibration standards
(3) inadequate calibration
(4) placing other things on top
(5) proper leveling
Environmental:
(1) static electricity
(2) electrical supply (if electrical)
(3) vibration
(4) air drafts
(5) temperature
(6) table or base instability