Metrological Deviation
Gradual and unwanted changes in the operating characteristics of a measurement system over time are a major source of measurement uncertainty in precision instruments. In sensor calibration, parameter drift represents the long-term shift in the internal coefficients or physical values that define the sensor’s response curve. This change occurs even when the instrument is stored under stable laboratory conditions, necessitating periodic recalibration to maintain traceability and to ensure that the sensor operates within its designated manufacturer tolerance specifications.
Environmental Action
Thermal cycling, mechanical shock, and material aging are the primary physical mechanisms that drive these shifts. As internal stresses within the sensor housing or the resistive elements relax over time, the physical properties of the components change. This relaxation directly leads to parameter drift, which modifies both the zero-point offset and the sensitivity of the instrument.
Calibration Correction
Detecting these changes requires comparing the instrument’s output against a primary standard at scheduled intervals. Calibration laboratories track these historical measurements to build a profile of the parameter drift over several months or years. Mathematical corrections can then be applied to the digital output to compensate for the anticipated rate of change between physical calibration events.
Systemic Uncertainty
Failing to account for these shifts introduces systematic errors that propagate through all subsequent measurements made with the device. If the parameter drift is non-linear, simple linear interpolation between calibration cycles will fail to capture the true behavior of the instrument. Maintaining a rigorous calibration history is therefore required for quantifying and bounding the uncertainty associated with this drift.