Instrument error refers to a measurement error inherited from a measuring instrument. It could be caused by manufacturing tolerances of components in the instrument, the accuracy of the instrument calibration, or a difference between the measurement condition and the calibration condition (e.g., the measurement is done at a temperature different than the calibration temperature).
Such errors are considered different than errors caused by different reasons; errors made during measurement reading, errors caused by human errors, and errors caused by a change in the measurement environment caused by the presence of the instrument affecting the environment.
