Overview
EN ISO 17657-1:2007 (ISO 17657-1:2005) provides guidelines for the measurement of welding current in resistance welding. It covers the equipment, terminology and basic measurement practices for calibrating and using welding current measuring systems applied to single‑phase alternating current (50 Hz or 60 Hz) and direct current. The standard is adopted by CEN and intended to support accurate determination of welding current and weld time in resistance‑welding processes.
Key Topics
- Scope and applicability
- Measurement and calibration guidance for welding current measuring systems used on single‑phase AC (50/60 Hz) and DC.
- Definitions of basic terms such as welding current, weld time, current flow time, reference/master meters, and certified reference equipment.
- System components
- Description of a welding current measuring system: current sensing coil (e.g. toroidal or Rogowski), integrator/amplifier, data processing unit and display/recorder.
- Alternative sensors referenced: non‑inductive shunt and other suitable sensors.
- Calibration and accuracy
- Emphasis that calibration should be performed on the complete set (sensor + integrator) to guarantee measurement accuracy.
- Practical note: for high‑accuracy measurements (better than ±0.5 %), the current sensing coil must be positioned exactly as during calibration.
- Factors affecting measurement scatter: sensor manufacturing variation, sensor placement, magnetic noise, temperature, integrator design and data processing algorithms.
- Measurement definitions and procedures
- Welding current is indicated as an r.m.s. value accumulated over the defined weld time; Annex A provides additional weld‑time definitions and calculation notes.
- Current flow time is defined for DC and is used for hold‑time considerations.
Applications and Who Uses It
- Welding equipment manufacturers (OEMs) - design and validate weld controllers and built‑in welding current meters.
- Quality assurance and production engineers - ensure process control, repeatability and traceability of weld current measurements.
- Calibration and test laboratories - perform system calibration and verification, using the standard’s guidance on calibration systems and reference meters.
- Standards/Compliance teams - integrate consistent measurement definitions into certification and inspection workflows.
- Research and development - develop and validate new sensors (coils or shunts) and integrator algorithms for resistance welding applications.
Related Standards
- ISO 17657 series:
- ISO 669 - Resistance welding equipment - mechanical and electrical requirements
EN ISO 17657-1:2007 is essential reading for anyone responsible for accurate current measurement, calibration and process control in resistance welding. Keywords: resistance welding, welding current measurement, current sensing coil, calibration, weld time, ISO 17657-1, EN ISO 17657-1:2007.