Metrology ensures quality, efficiency, and safety. This guide covers measurement standards, from international to working, and highlights 3D metrology’s role in creating precise models for inspection and reverse engineering.
Metrology, the science of measurement primarily focuses on establishing, maintaining, and applying measurement standards. It is used in almost all major industries including aerospace manufacturing, and automotive to ensure that parts meet all requirements.
A standard is a physical representation of a measurement unit, defined using either a material standard or natural phenomena as a reference. Different standards exist for various measurement units, and the Bureau International des Poids et Mesures (BIPM) in Sèvres, France, oversees their maintenance.
Measurement standards are classified into categories according to their functions and applications.
International standards are defined by international agreements and represent fundamental units of measurement. They are checked and evaluated regularly against realizations of fundamental constants or primary standards. Due to their critical role, international standards are not directly accessible to ordinary users.
Example:
Historically, the international ohm was defined as the resistance of a mercury column (14.4521 g, 106.300 cm long, with a constant cross-sectional area) kept in melting ice. However, resistance is now measured using the quantum Hall effect, which ties it to universal constants for greater precision.
The introduction of the International System of Units (SI) in 1948 replaced earlier artifact-based definitions with units derived from fundamental physical constants. These units provide higher accuracy and stability.
Primary standards are the most accurate and stable standards in metrology. They define units of measurement in absolute terms, independent of any other standard.
Examples:
-Kilogram (kg): The SI unit of mass is now defined by fixing the numerical value of Planck’s constant \((h = 6.62607015 \times 10^{-34} \ \mathrm{Js})\), replacing the earlier artifact-based definition using a platinum-iridium alloy cylinder.
-Meter (m): Defined as the distance light travels in a vacuum in \(1/299,792,458\) of a second.
-Volt (V): Defined using the Josephson effect, which relates voltage to fundamental constants like Planck’s constant and the electron charge.
Secondary standards are less accurate than primary standards but more accessible. Laboratories use them to:
- Calibrate measuring instruments.
- Check the accuracy of tools and other standards.
Although secondary standards are traceable to primary standards, they are more cost-effective and practical for day-to-day use.
Working standards are calibrated against secondary standards and are used regularly in laboratories to:
- Govern measurements.
- Calibrate instruments.
- Verify measurement methods.
These standards are essential for routine applications and can act as backups when secondary standards are unavailable or undergoing recalibration.
Engineers use 3D metrology in manufacturing, automotive, aerospace, and other industries to measure physical objects in three dimensions so they can better understand their shape, size, and geometry.
Parts are scanned using 3D scanners. Advanced scanners capture every detail, enabling engineers to create highly accurate 3D models, which can be used to identify areas of improvement.
Metrology-grade 3D scanners are capable of capturing millions of data points in seconds. Data points can be used to create a 3D model of the scanned object.
Thanks to these advances in 3D metrology, metrology-grade 3D scanners are faster, more accurate, and versatile than ever.
3D metrology is widely used in different industries to ensure that parts meet all specifications. It can help identify defects in the early stages of production, reducing waste. Many manufacturers use 3D metrology to reverse engineer legacy parts or parts for which original design documents are unavailable. It enables early validation of designs, ensuring manufacturers can mass produce with confidence.
Need help managing your 3D scanning project? Call 708-429-4887.
You'll find all the detailed service information you need in one brochure.
Download Brochure
Get a quote within 24-hours and keep your project on schedule.
Get a Quote
Our Nel PreTech engineers are ready to get started on your product challenges.
Ask an Engineer
Download the ultimate CT Scanning Buyer's Guide to improve understanding, time, and efficiency in your scanning needs. Over 50 Pages of useful data and case studies.
Download Now
