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Measurement Accuracy Requires a Calibration Program
When you use a measurement instrument, you assume it is giving you an accurate measurement.
- However, that is not always the case. Even normal use and wear of the device can affect its measurements.
- Combine normal wear and tear with the realities of a manufacturing environment (such as oil, metal or plastic chips, and the chance that the gage or instrument may be dropped or jolted) and you start to realize the importance of a good calibration system.
A formal measurement device management program including a rigorous calibration program is required to ensure measurement accuracy.
Components of a good measurement device management program include:
- Instrument inventory lists
- Assessment of testing needs
- Calibration procedures including the use of contracted calibration services if needed
- Records of device maintenance history, calibration records, and traceability documentation
- Management of calibration standards
- Identification of training requirements & related resources
- System audit requirements
Calibration Systems
- ISO 10012-1 (titled, “Quality Assurance Requirements for Measuring Equipment, Part 1, Metrological Confirmation System for Measuring Equipment) and ANSI/NCSL Z540-1 define the requirements for the establishment and maintenance of a calibration system designed to control the accuracy of measuring and test equipment and measurement standards.
- A Calibration Record should include:
- Description of the device
- Characterization and condition of the measuring instrument
- Date of calibration
- Calibration procedure
- Environmental conditions during calibration
- Measurement and results supported by data
- Identification of any failures
- A traceability statement
- A statement of the estimated uncertainty
- It is important to have written procedures for calibration procedures. Steps to check the calibration of a device include:
- Define the temperature and relative humidity requirements.
- Visually examine the device for damage and wear.
- Clean the measuring surfaces being careful not to damage them.
- Check the device using the appropriate standards. If the device has a variable scale, check the low, mid-point, and high-end of the range.
If checks indicate the measuring device is not accurate, remove the device from service.
- Initiate action to adjust and recalibrate if possible.
- Document the results of the calibration.
- Attach the appropriate calibration sticker to the instrument.
- If the device cannot be fixed, tag it with an “inactive” sticker and destroy it if that is appropriate.
