Overview
ISO 764:2020 - "Horology - Magnetic resistant watches" is the international standard that specifies minimum requirements and test methods for watches designed to resist everyday magnetic fields. It defines both ordinary magnetic resistant watches (tested at 4 800 A/m) and enhanced magnetic resistant watches (designed for stronger fields, ≥16 000 A/m), and it prescribes the marking manufacturers may apply.
Key topics and technical requirements
- Scope and definitions: clarifies terms such as magnetic resistant watch, enhanced magnetic resistant watch and residual effect (difference in rate before and after exposure).
- Performance criteria:
- Watches must not stop during magnetic field application (mechanical and electronic).
- For mechanical watches, limits on residual effect (rate change after exposure) depend on case size (stricter limits for larger cases).
- Electronic watches: no stepper motor may stop; multiple motors must all continue running.
- Test conditions and environment:
- Tests on finished products, without removable bracelets.
- Room temperature: 23 °C ± 5 °C; watch temperature during rate measurement must not vary by more than ±2 °C.
- Test apparatus and fields:
- Homogeneous, continuous direct current magnetic fields with admissible variation 0% to +5%.
- Standard test value: 4 800 A/m (daily magnetic fields); enhanced tests in Annex A use higher field strengths.
- Test procedure (mechanical watches):
- Demagnetize in three orthogonal directions (3H–9H, 12H–6H, CH–FH) before initial rate measurement.
- Measure initial rate for at least 180 s (CH position, per ISO 3158).
- Apply field progressively, observe for 60 s (or longer for watches without second hands), remove field, then measure post-test rate and calculate residual effects.
- Marking: authorized markings (e.g., "magnetic resistant" in multiple languages) and guidance on placement.
Applications and who uses it
ISO 764:2020 is used by:
- Watch manufacturers and designers to certify magnetic resistance and apply correct markings.
- Quality assurance and production testing teams to validate compliance during manufacturing.
- Independent test laboratories performing standardized magnetic resistance tests.
- Retailers and consumers seeking objective information about a watch’s resistance to everyday magnetic fields.
Practical application includes product specification, marketing claims about antimagnetism, and regulatory/conformity documentation.
Related standards
- ISO 3158 - Timekeeping instruments: symbolization of control positions (referenced for rate measurement positions).
- Annexes in ISO 764:2020 include a flow chart for testing (Annex B) and guidance on distance relationships to magnetic-field sources (Annex C), useful for interpreting real-world exposure.
Keywords: ISO 764:2020, magnetic resistant watches, watch magnetic resistance testing, horology standard, antimagnetism, watchmakers, watch testing laboratory.
