ISO 7500-1:2018

Overview

ISO 7500-1:2018 - "Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Calibration and verification of the force‑measuring system" defines requirements for the static calibration and verification of force‑measuring systems in tension/compression testing machines. The standard covers a general machine inspection, calibration of the force‑measuring system, and confirmation that performance meets limits for a specified class. Note: this part addresses static calibration only - calibration values are not necessarily valid for high‑speed or dynamic testing.

Key topics and requirements

• General inspection of the testing machine and force application accessories (see Annex A). Calibration is carried out only if the machine is in good working order.
• Calibration of the force‑measuring system for each force range and all force indicators in use. Instruments must have traceability to SI units.
• Use of force‑proving instruments in accordance with ISO 376; dead weights may be used for forces below the smallest proving instrument. When using dead weights, relative force error shall be within ±0.1%.
• Calibration procedure elements:
  • Determination of resolution (analogue: pointer vs scale spacing; recommended pointer-to-scale ratios 1:2, 1:5 or 1:10; spacing ≥ 2.5 mm for one‑tenth divisions).
  • Alignment of the force‑proving instrument and temperature compensation.
  • Conditioning of machine and instrument prior to measurement.
  • Application of discrete constant forces (increasing and/or decreasing series) and verification across ranges (overlap between instruments).
  • Verification of accessories (recorders, pointers) and effects such as piston position differences.
• Performance assessment metrics include relative indication error, repeatability error, relative reversibility error, and agreement between two force‑proving instruments.
• Reporting and intervals: verification report requirements and recommended intervals between verifications are specified. Annex C discusses uncertainty of calibration results.
• Safety note: some tests can create hazardous conditions - follow appropriate safety procedures.

Applications and who uses it

ISO 7500-1:2018 is used by:

• Calibration and metrology laboratories performing force calibration and verification.
• Materials testing laboratories and quality control departments that operate tensile/compression machines.
• Manufacturers of testing machines and force‑measuring instruments for design verification and compliance.
• Certification, inspection and accreditation bodies assessing machine performance and traceability. Practical uses include ensuring accurate tensile/compression test results, maintaining traceability of material test data, supporting quality assurance in R&D and production, and meeting regulatory or customer conformity requirements.

Related standards

• ISO 376 - Calibration of force‑proving instruments used for verification of uniaxial testing machines (normative reference).
• Other parts of the ISO 7500 series (see ISO website for a full list).

Keywords: ISO 7500-1:2018, calibration, verification, tension/compression testing machines, force‑measuring system, static uniaxial testing, ISO 376, force‑proving instrument, metrology, testing machine class.