stability

**Stability** in metrology is the **consistency of measurement results over time** — a stable measurement system produces the same results today, next week, and next month when measuring the same artifact, indicating that the gage is not drifting or degrading. **Stability Assessment** - **Method**: Measure the same reference standard (master part) periodically — daily, weekly, or each shift. - **Control Chart**: Plot measurements on a control chart — detect drift, trends, or sudden shifts. - **Time Frame**: Assess stability over the period between calibrations — gage must remain stable between cal cycles. - **Environment**: Temperature, humidity, and vibration changes can affect stability — control the environment. **Why It Matters** - **Calibration Interval**: Stability determines how often the gage must be calibrated — unstable gages need frequent calibration. - **Drift**: Slow drift can go undetected without stability monitoring — causing gradually increasing measurement error. - **Semiconductor**: Fab metrology tools run 24/7 — daily stability checks using "golden wafers" are standard practice. **Stability** is **the measurement staying true over time** — ensuring the gage produces consistent results throughout its calibration interval.