ISO 9513 — Calibration of extensometer systems for uniaxial testing

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ISO 9513 specifies how to calibrate the extensometer systems used to measure strain in uniaxial testing of metals. The calibration assigns the extensometer a class that determines which properties it can be trusted to report. To match an extensometer class to the results you must record, talk with our team.

What ISO 9513 Calibrates

The standard evaluates how accurately an extensometer measures displacement over its gauge length. A reference length-measuring device applies known displacements, and the extensometer response is compared against them to determine error, resolution, and class.

Extensometer Classes

Calibration places the extensometer in a class by its permitted error. Tighter classes are needed for proof-strength and modulus work:

Table 1. ISO 9513 extensometer classes by permitted error.
Class Typical use
Class 0.5 Proof strength and modulus, where small strains must be resolved accurately
Class 1 General yield and elongation measurement
Class 2 Larger-strain measurements with wider tolerance

Why Extensometer Class Matters

Yield-related results are only as good as the strain measurement behind them. Methods such as ISO 6892-1, especially under strain-rate (Method A) control, depend on an extensometer of a suitable class. A current ISO 9513 calibration is what makes those strain-based results defensible.

Reading the Designation

Cited as ISO 9513:YYYY. Confirm the edition, since class limits and procedures can change between revisions.

Related Standards

ASTM E83 is the ASTM practice for extensometer verification, ISO 7500-1 verifies the machine force system, and ISO 6892-1 is a common test method that relies on calibrated extensometry.

Request a Quote

Need extensometers calibrated or matched to a strain requirement? Request a quote and our team will help you build a system matched to your strain range and extensometer class.


TensileMill CNC products for ISO 9513

Our specimen-preparation systems and testing equipment compatible with ISO 9513:


Equip your lab for ISO 9513 with TensileMill CNC

From specimen preparation to the test itself, TensileMill CNC supports the full ISO 9513 testing chain. For this work we supply load cells, alignment hardware, and the reference setups used for machine and extensometer verification. Share your material mix and throughput, and we will recommend a setup that fits ISO 9513.