ISO 20495:2018

Overview

ISO 20495:2018 specifies performance and test methods for skin electrical resistance measurement devices used in Traditional Chinese Medicine (TCM). It applies to non‑invasive devices that apply an electrical signal to acupuncture points or specific body surface points to detect skin electrical resistance. The standard defines measurable ranges, accuracy, safety and biocompatibility requirements, and test procedures. It does not cover software or medical analysis functions. Annex A provides additional guidance and rationale.

Key topics and requirements

• Measurable range: devices shall measure skin electrical resistance from 100 Ω to 10 kΩ.
• Measurement accuracy: measured values (Ω, V, A or relative) must be within ±10% of actual value.
• Detection electrical signal: set vs actual voltage/current error must be within ±10%.
• Detection voltage limit: RMS open‑circuit voltage shall not exceed 24 V.
• Detection current limit: RMS short‑circuit detection current shall not exceed 0.5 mA.
• Electrodes:
  • Exploratory (contact) and auxiliary (reference) electrodes defined; auxiliary effective area ≥ 300 mm².
  • Electrode force indication devices must indicate force within ±10%.
  • Force sensing switch repeatability error for exploratory electrodes must be ≤ ±10%.
• Safety and compatibility: devices must meet electrical safety and EMC requirements of IEC 60601‑1 and IEC 60601‑1‑2.
• Biological evaluation: materials in contact with skin must be assessed per ISO 10993‑1 (biocompatibility evidence via testing, literature, or proven clinical use).
• Testing methodology: the standard prescribes how to select test points, use non‑reactive resistors for calibration checks and calculate repeatability/error metrics.

Applications and who uses the standard

ISO 20495:2018 is practical for:

• Manufacturers of TCM diagnostic/measurement devices to design and certify product performance and safety.
• Regulatory and quality assurance teams preparing technical documentation and conformity evidence.
• Test laboratories performing performance verification, electrical safety and EMC testing.
• Clinicians and TCM practitioners seeking devices with established accuracy, safety and biocompatibility.
• Product designers integrating electrodes, force sensors and signal sources to meet device limits.

Using ISO 20495 helps ensure reliable, repeatable skin electrical resistance measurements and supports regulatory compliance and market acceptance.

Related standards

• IEC 60601‑1 - Medical electrical equipment - basic safety and essential performance
• IEC 60601‑1‑2 - Electromagnetic compatibility for medical devices
• ISO 10993‑1 - Biological evaluation of medical devices (biocompatibility)

For device implementation and rationale, consult Annex A of ISO 20495:2018.