EN 3475-805:2002

Overview

EN 3475-805:2002 is a European standard that defines test methods for measuring the characteristic impedance of electrical cables used in aerospace applications. Issued by CEN and prepared by the European Association of Aerospace Manufacturers (AECMA), this standard ensures reliable and consistent testing procedures crucial for aircraft electrical cable performance. It is designed to be used alongside EN 3475-100, which covers general test methods for aerospace cables.

Characteristic impedance is a fundamental electrical parameter that affects signal integrity, electromagnetic compatibility, and overall cable performance in aviation systems. Accurate measurement following EN 3475-805:2002 helps manufacturers and quality assurance teams verify compliance with strict aerospace standards.

Key Topics

• Scope
  Specifies standardized methods for measuring the characteristic impedance of aerospace electrical cables.

• Reference Standards
  Needs to be used in conjunction with EN 3475-100 (General test methods) and EN 3475-804 (Velocity of propagation).

• Test Methods

  • Method A: Impedance bridge measurement on coaxial cables
    • Uses input impedance with cable ends open-circuit and short-circuit to calculate characteristic impedance.
    • Requires cable samples of 3 meters or longer.
  • Method B: Reflectometer measurement on coaxial cables
    • Measures reflection coefficient at one meter from cable input; calculates characteristic impedance from this value.
  • Method C: Measurement on shielded symmetric cables
    • Utilizes a vector network analyzer and balun for measuring reflection coefficients on balanced cables.
    • Includes detailed calibration procedures for accurate results.

• Equipment Requirements

  • Impedance measuring bridge
  • Reflectometer or vector network analyzer
  • Balun with specific impedance matching characteristics

• Measurement Formulas
  Characteristic impedance (Zc) is derived using measured input impedances or reflection coefficients, with precise mathematical formulas provided for each method.

• Compliance
  The measured characteristic impedance must fall within limits specified in the respective product standards to ensure cable suitability for aerospace use.

Applications

This standard is essential for aerospace manufacturers, test laboratories, and quality control departments involved in:

• Aircraft Electrical Cable Certification
  Verifying that cables meet aerospace electrical performance requirements before installation.

• Signal Integrity Assurance
  Ensuring minimal signal reflections and losses in critical avionics communication and control systems.

• Research and Development
  Developing new aerospace cable designs with verified characteristic impedance values for enhanced performance.

• Maintenance and Troubleshooting
  Measuring cable impedance in situ to detect degradation or faults affecting electrical signal transmission in aircraft.

Related Standards

• EN 3475-100 – Aerospace series cables: General test methods, providing foundational procedures linked to Part 805.
• EN 3475-804 – Test methods for velocity of propagation in aerospace cables, often performed alongside impedance measurement.
• AECMA Specifications – Various aerospace cable manufacturing and testing guidelines harmonized with EN 3475-series standards.
• IEC and MIL Standards – Complementary international and military aerospace cable standards relating to electrical performance and environmental testing.

By adhering to EN 3475-805:2002 test methods, aerospace stakeholders ensure electrical cables exhibit consistent characteristic impedance, critical to maintaining performance, safety, and reliability in modern aircraft electrical systems. This standard supports efficient quality control and compliance with international aerospace manufacturing requirements.