The core of ASTM E83 is the classification table. Extensometers are not simply "pass" or "fail"; they are categorized into classes based on their error limits relative to the strain being measured. The standard defines six primary classes, typically represented by letters.
The physical calibration must be performed using a certified verification apparatus (often called an extensometer calibrator or micrometer tower). This apparatus must be highly accurate—typically traceable to national standards like NIST—and must have an accuracy at least five times greater than the extensometer being verified. Step-by-Step Verification Procedure
The actual device attached to the specimen (e.g., clip-on, contact, or non-contact/video extensometers). astm e83 pdf
Utilizing a universally accepted verification standard ensures that a material tested in Asia, Europe, or North America yields identical, comparable data.
The scope of ASTM E83 is specific to systems that measure strain, a dimensionless quantity that represents deformation relative to an original length. It provides a standardized method for "verification," which is the process of comparing an extensometer's output against known, traceable displacements generated by a high-precision apparatus. Importantly, the standard is clear that it is not intended to be a complete purchase specification, but rather a performance benchmark. The core of ASTM E83 is the classification table
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: Use tools like Adobe Acrobat , Microsoft Word, or Google Docs to open and save the PDF as an editable text or Word document. The physical calibration must be performed using a
| | Typical Use Case | | :--- | :--- | | Class A | Highest precision; used in research, calibration laboratories, and critical applications | | Class B-1 | High accuracy suitable for most general testing requirements | | Class B-2 | Medium accuracy for routine quality control | | Class C | Lower accuracy for less critical testing | | Class D | Low accuracy for preliminary or educational use | | Class E | Lowest accuracy, with correspondingly higher permissible errors |
Extensometer systems are classified based on the maximum allowable error of the indicated strain and their overall displacement resolution. When a calibration engineer evaluates a system, they assign it one of six distinct classes: Extensometer Class Maximum Error of Indicated Strain Resolution Requirement Typical Application Extremely strict limits Exceptionally high resolution Specialized research, high-precision calibration standards Class B-1 of reading or fixed limit Modulus of elasticity testing for aerospace alloys Class B-2 Slightly higher fixed error allowance Standard metals testing, yield strength ( Rpcap R sub p ) determination Class C Moderate error threshold General tension/compression tests, plastic deformation Class D Higher error threshold High-elongation materials, polymers, elastomers Class E Maximum permissible error tier Broad structural tear/break limits
The verification process outlined in the ASTM E83 PDF involves comparing the readings of the extensometer against a highly accurate reference device, known as a calibration apparatus or displacement standard. Key Steps in the Verification Procedure:
The 2023 version added Annex A1 , specifically for optical and non-contact extensometers. 🔍 Verification Classes (Accuracy Limits)