Metrology and Calibration: What Are They?

By Owais AliReviewed by Lexie CornerMar 26 2025

Metrology is the science of precise measurement. It ensures accuracy and consistency across scientific, industrial, and engineering fields. Calibration is the process of aligning measurement instruments with known reference standards to maintain accuracy and reliability.

Both are essential for consistency in materials testing, quality control, and research and development (R&D), where precise measurements directly affect product performance and regulatory compliance.

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What is Metrology?

Metrology, derived from the Greek words metron (measurement) and logos (study), is the science of measurement and its application. It establishes a framework for achieving accurate, reliable, and comparable measurements across disciplines, ensuring consistency at defined uncertainty levels.^1,2

In industries such as aerospace, automotive, and medical manufacturing, accurate material characterization supports product performance, reliability, and regulatory compliance.

However, environmental conditions, operator techniques, and inconsistencies in calibration can lead to inaccurate or non-comparable data. Metrology addresses these issues by promoting standardized practices that ensure precision and reproducibility.

Key Measurement Areas in Metrology

Dimensional Metrology

Dimensional metrology ensures that manufactured components meet precise tolerances by measuring length, area, volume, flatness, and roundness.

Advanced techniques such as coordinate measuring systems (CMSs), laser trackers, and X-ray computed tomography allow for high-precision, non-contact measurements. These methods reduce errors associated with manual tools.

When combined with traceable length standards and form measurement methods, these technologies help maintain consistency, detect geometric deviations, and improve reproducibility in manufacturing. Error separation techniques, such as reversal methods, are also used to eliminate systematic errors and further enhance measurement precision.⁴

Mechanical Metrology

Mechanical metrology measures and analyzes key material properties, such as hardness, and tensile strength.

Hardness testing techniques, including Brinell, Rockwell, and Vickers tests, assess a material’s resistance to deformation, while tensile strength evaluation using Universal Testing Machines (UTMs) determines a material’s ability to withstand applied forces.

These techniques help assess material durability and suitability, ensure quality assurance, and support the development of reliable engineering components.⁵

Thermal Metrology

Thermal metrology involves measuring properties such as heat capacity, thermal expansion, and thermal conductivity by monitoring temperature variations along a controlled thermal gradient.

Thermal metrology methods are classified as steady-state or transient.

• Steady-state methods determine thermal conductivity once a stable temperature gradient is established, following Fourier's law.
• Transient methods analyze temperature variations over time and require heat capacity data for accurate characterization.

Traditional contact-based steady-state techniques, such as the guarded hot plate method, measure heat flow through materials but are less effective for micro- and nanoscale films due to bulk material influence. However, advances in lithography have improved accuracy by integrating patterned metal heaters and sensors for localized Joule heating, enhancing steady-state measurements at smaller scales.

Non-contact opto-thermal transient methods, including Laser Flash, eliminate sensor placement constraints by using laser heating to track temperature changes dynamically. However, they are less effective for thin films where interfacial resistance dominates.⁶

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What is Calibration?

Calibration involves maintaining instrument accuracy by configuring it to deliver results within an acceptable range. It minimizes sources of measurement error and ensures reliable performance.

The process typically involves testing samples with known values, called calibrators, to establish a correlation between the instrument's measurement method and these reference values. This effectively "teaches" the instrument to produce more precise results when analyzing unknown samples.

Calibration is generally performed using a limited number of calibrators at key points within the instrument's operating range to balance accuracy with efficiency. While using a larger number of calibrators could enhance precision, the additional time and effort required may not justify the marginal performance gains.

It is recommended that instruments should be calibrated according to the manufacturer's specified reference points to achieve optimal accuracy and avoid inherent measurement errors.^2,7

Common Calibrated Instruments in Materials Science

Spectrometers

Spectrometers analyze light properties in scientific and industrial applications, enabling precise material characterization based on optical responses. However, maintaining measurement accuracy requires proper calibration, which corrects errors caused by fluctuations in light intensity, detector sensitivity, and optical alignment.

Their calibration involves calibrating the light source to ensure accurate intensity measurement, calibrating the wavelength to identify precise spectral features, calibrating the detector to compensate for sensitivity drift, and aligning the optical elements to prevent spectral distortion.

Various calibration techniques, such as spectral line, absorption/emission, fiber-optic, and external source calibration, enhance measurement precision. Software-based calibration automates adjustments for improved efficiency.

Moreover, optical components of spectrometers are regularly calibrated to maintain accuracy and long-term reliability amid environmental and operational factors.^8,9

Hardness Testers

The accuracy of hardness testing machines is essential for reliable material analysis. They require calibration upon installation, after modifications, and during routine maintenance. In addition to initial calibration, periodic daily or weekly verification ensures continued accuracy within defined tolerances.

Their calibration process involves direct verification, which assesses key measurement variables such as test force, indenter geometry, and depth or diameter measurement systems, and indirect verification, which evaluates accuracy by comparing test results with calibrated hardness test blocks.

This ensures that hardness testing methods such as Rockwell, Vickers, and Brinell, which rely on precise force application and accurate indentation measurements, produce reliable and consistent results by minimizing errors.

To maintain accuracy, standard test blocks, such as steel or tungsten carbide blocks, are only used on designated surfaces to prevent measurement errors caused by surface irregularities or contamination.¹⁰

Thermal Analyzers

Calibration in thermoanalytical measurements ensures that instruments accurately measure temperature changes and heat flow. These instruments are calibrated using reference materials with well-characterized thermal properties to maintain measurement precision and reliability.

For example, differential scanning calorimeters (DSC) calibration involves measuring phase transitions of reference materials (allium or indium) with known melting points and enthalpies, following standards such as ASTM E 967-97 and ASTM E 968-99.

Whereas thermogravimetric analyzers (TGA) are calibrated using reference materials with well-defined decomposition temperatures or Curie point materials such as nickel and cobalt, which exhibit sharp and reversible magnetic transitions, ensuring precise thermal transition measurements.^11,12

Importance Of Uncertainty Analysis

Even after calibration, inherent errors persist due to measurement accuracy, model assumptions, and parameter estimation limitations, as physical systems rely on simplifications that introduce systematic deviations.

Additionally, noise and measurement inaccuracies prevent a perfect match between model predictions and real-world behavior. This leads to uncertainty, where multiple parameter sets can produce similar outputs—a non-uniqueness optimization problem.

Uncertainty analysis quantifies how these variations affect model predictions by assigning probability distributions to parameters, capturing a range of possible outcomes. This enhances reliability assessments, identifies potential risks, reduces errors, and enhances the accuracy of complex system interpretations.¹³

Why It Matters in Materials Science and Engineering?

Ensuring Repeatability

Ensuring repeatability is essential in research and industrial processes, as consistent measurements are critical for quality control, process optimization, and compliance with technical standards.

Calibration helps maintain repeatability by detecting and correcting instrument drift caused by wear, environmental changes, and prolonged use. It also aligns measurements with traceable standards from institutions like the National Institute of Standards and Technology (NIST).

However, operator technique significantly impacts repeatability, particularly in optical and 3D metrology, where standardized measurement protocols and proper training help minimize reproducibility errors.¹⁴

Regulatory Compliance

Many industries comply with strict quality and safety standards set by organizations such as the FDA, ISO, and ASTM, requiring calibrated instruments to verify product performance and regulatory adherence.

For example, ISO/IEC 17025 ensures quality management and technical competence in calibration laboratories, while ASTM E74 and ASTM E898-20 provide industry-specific calibration guidelines for force-measuring and weighing instruments.

These standards ensure measurement reliability in critical applications, such as propulsion testing in UAVs and aircraft, where repeatability and precision over extended testing periods are essential.

To maintain compliance, industries must implement documented calibration procedures, trace measurements to international standards, and regularly assess measurement uncertainties using reference artifacts from organizations like NIST.^15,16

Preventing Defects

Small measurement deviations in the aerospace, automotive, and medical industries can compromise safety and performance, leading to defective components, costly recalls, and regulatory risks. This emphasizes the need for stringent measurement accuracy and quality control.

Therefore, metrology and calibration are vital in detecting and correcting deviations, ensuring standardized techniques, and maintaining measurement reliability over time.

These practices uphold structural integrity, consistent quality, and regulatory compliance while preventing errors, mitigating risks, enhancing product reliability, and ensuring long-term success in competitive markets.¹⁷

For further reading on calibration standards, uncertainty analysis, and precision measurement techniques, explore the following resources:

• Why it is Important to Measure the Uncertainty of Spark Measurements
• Precision Density Determination: Unveiling the Science of Accurate Volume Measurement Through Density Cups
• Measurement System Analysis Procedure for Spectroscopy
• Gage R&R for Repeatability and Reproducibility
• The ABC of Viscosity Standards

References and Further Reading

1. NIST. (2025). Metrology. [Online] NIST. Available at: https://www.nist.gov/metrology
2. Bringert, G. (2021) Calibration and metrology. In: N. E. Nash (ed.) Handbook of Validation in Pharmaceutical Processes, 4th ed. CRC Press. Available at: https://www.taylorfrancis.com/chapters/edit/10.1201/9781003163138-8/calibration-metrology-g%C3%B6ran-bringert
3. ZEISS. (2025). Metrology For Mechanical Engineering. [Online] ZEISS. https://www.zeiss.com/metrology/en/industries/machinery.html
4. Leach, R., Ferrucci, M. and Haitjema, H. (2020) Dimensional metrology. In: CIRP Encyclopedia of Production Engineering. Available at: https://www.academia.edu/download/62238492/2020_ReferenceWorkEntry_20200229-75968-5xgmjv.pdf
5. Wiederhorn, S.M., et al. (2011) Mechanical properties. In: Czichos, H., Saito, T. and Smith, L. (eds.) Springer Handbook of Metrology and Testing. Springer. Available at: https://doi.org/10.1007/978-3-642-16641-9_7
6. Hopkins, P. (2025). Introduction to Thermal Analysis and Metrology. [Online] Laser Thermal. Available at: https://laserthermal.com/learning-center/introduction-to-thermal-analysis-and-metrology/
7. US EPA. (2013) Chapter 12 Calibration. In: Handbook for Air Pollution Measurement Systems: Volume II. Ambient Air Quality Monitoring Program. [Online] US Environmental Protection Agency. Available at: https://www3.epa.gov/ttnamti1/files/ambient/pm25/qa/vol2sec12.pdf
8. Rabbani, R. (2023) Spectrometer Calibration: Ensuring Accuracy in Spectral Measurements. [Online] Lisun Group. Available at: https://www.lisungroup.com/news/technology-news/spectrometer-calibration-ensuring-accuracy-in-spectral-measurements.html?srsltid=AfmBOooDCVI8vIcTi9oFT77qfsfTlsm14viEHXwj9ZHzU0C7FFeBL90B
9. Tengstrand, E., Solberg, L.E., Dankel, K., Lintvedt, T.A., Afseth, N.K. and Wold, J.P. (2024) Calibration transfer between different spectrometers by wavelength correspondence. Vibrational Spectroscopy, 132, 103667. Available at: https://doi.org/10.1016/j.vibspec.2024.103667
10. EMCO-TEST. (2023) Calibration & Standards – Hardness Testing. [online] Available at: https://www.emcotest.com/en/hardness-knowledge/calibration-standards
11. Slager, T. and Prozonic, F. (2005) Simple methods for calibrating IR in TGA/IR analyses. Thermochimica Acta, 426(1–2), pp.93–99. Available at\; https://doi.org/10.1016/j.tca.2004.07.022
12. Greenbeck, J.F. and Taylor, C.W. (2013) Standard Cleaning and Calibration Procedure for TGA-50(H) and TGA-51(H). [Online] Shimadzu. Available at: https://www.shimadzu.com/an/sites/shimadzu.com.an/files/pim/pim_document_file/applications/application_note/9718/app168.pdf
13. Abbaspour, K.C., Vaghefi, S.A. and Srinivasan, R. (2017) A guideline for successful calibration and uncertainty analysis for soil and water assessment: A review of papers from the 2016 International SWAT Conference. Water, 10(1), p.6. Available at: https://doi.org/10.3390/w10010006
14. Krishnan, K.M. (2021) Principles of Materials Characterization and Metrology. Oxford University Press. Available at: https://doi.org/10.1007/s10853-022-07140-9
15. Alexander, P.A. (2013) Calibration: What is it and why it matters? An introduction to the special issue on calibrating calibration. Learning and Instruction, 24, pp.1–3. Available at: https://doi.org/10.1016/j.learninstruc.2012.10.003
16. ASTM. (2019) Standard Practices for Calibration and Verification for Force-Measuring Instruments. [online] ASTM International. Available at: https://store.astm.org/e0074-18e01.html
17. Krishnamurthy, L. and Raghavendra, N.V. (2013) Engineering Metrology and Measurements. [online] Available at: https://www.bbau.ac.in/dept/UIET/Study%20MAterials%20for%20EME-403.pdf

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