Temporal Instability
Long-term performance trends recorded in sensor calibration logs quantify monotonic baseline offset changes occurring over months or years. In high-accuracy measurement equipment, secular drift describes non-periodic, irreversible changes in zero-point calibration caused by structural material aging. This continuous parameter operates independently of short-term thermal fluctuations or transient environmental noise.
Calibration schedules track offset movements over extended operating periods to maintain measurement integrity.
Relaxation Mechanism
Atomic dislocation movement within sensing elements drives physical dimensional shifts under permanent mechanical stress. Microstructural relaxation in resistor alloys and glass-to-metal seals alters internal strain conditions, producing steady resistance changes. Pre-conditioning processes like thermal burn-in accelerate early relaxation phases before final calibration occurs.
Post-treatment aging reduces subsequent drift rates but cannot eliminate long-term lattice restructuring. Signal conditioning electronics cannot distinguish physical sensor aging from genuine input signal changes, requiring periodic hardware zero adjustments.
Environmental Influence
Operating humidity variations alter packaging stress distributions, modifying baseline outputs. Moisture absorption in epoxy encapsulants induces mechanical expansion, exerting parasitic forces on silicon dies. Hermetic glass-to-metal sealing isolates sensing components from atmospheric moisture, reducing environmentally induced aging rates.
Recalibration Interval
Traceable calibration standards establish maximum allowable drift limits before instruments require zero adjustment or sensor replacement. Calibration certificates plot historical offset trajectories to forecast remaining operational lifetime within tolerance bounds. Statistical control charts evaluate recalibration data, extending or shortening inspection cycles based on measured drift stability.
Sensor designs exhibiting predictable drift characteristics enable automated software compensation based on historical time constants.
