instability (with reference to instrumentation)

https://doi.org/10.1351/goldbook.I03061
A change which takes place in an instrument @R05189@ 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 @D01859@ 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 @R05189@ 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 [Terms] [Paper]