Calibration Troubleshooting Use measurement history, independent checks, process evidence, and calibration data to separate instrument problems from process drift. Contents Is the Instrument Failing, or Is the Manufacturing Process Changing? Start with the measurement trend Check the measurement system Compare measurement and process data Use controlled checks Do not assume the cause Decide what needs correction Investigation checklist Continue the investigation Is the instrument failing, or is the manufacturing process changing? A measurement trend changes over time, but the reason isn't always clear. The instrument might be changing. The manufacturing process could also be altering. Additionally, the measurement method may influence the results. Start with the measurement trend. Begin by reviewing recorded measurements. Look at results over time to find a meaningful pattern. Check for: Changes in measured values Steady movement in one direction Unexpected shifts Va...