A change which takes place in an instrument
reading over a stated period of unattended operation for a given value of the air quality
characteristic. It can be characterized by the variation with time of its mean, specifying
the
drift and by the dispersion. Span instability is the change which takes place in instrument
span over a stated period of unattended operation. Zero instability is the change
in instrument
reading in response to a zero sample over a stated period of unattended operation.
Source:
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2197