Overview
ISO 17657-1:2005 - "Resistance welding - Welding current measurement for resistance welding - Part 1: Guidelines for measurement" provides guidance on measuring and calibrating welding current and weld time for single-phase alternating current (50 Hz or 60 Hz) and direct current (DC). The standard defines basic terms, describes a welding current measuring system (sensor, integrator/amplifier, data processing and display) and gives practical guidance for selection, testing and calibration of measuring systems including welding current meters and current sensing coils.
Key topics and technical requirements
- Scope and applicability: Measurement and calibration guidance for resistance welding using single‑phase AC (50/60 Hz) or DC; applies to welding current meters, sensing coils, shunts and other suitable sensors.
- System components: Welding current measuring system = current sensor (e.g., current sensing coil, non‑inductive shunt, Hall device), integrator/amplifier, data processing unit and display/recorder.
- Sensor types: Flexible and rigid current sensing coils are described; coils (toroidal/Rogowski) are predominant for secondary‑circuit measurement.
- Calibration as a set: For accurate results the sensor and integrator/amplifier should be calibrated together. If calibrating the sensor alone, the calibration input impedance must match the welding meter’s input.
- Accuracy factors: Measurement scatter can result from sensor manufacturing or winding distortion, sensor position, magnetic noise, temperature, integrator design and differing start/finish time definitions for RMS calculation. For very high accuracy (better than ±0.5%), the coil must be positioned exactly as during calibration.
- Sensor selection criteria: Sensitivity/conversion coefficient, maximum output voltage, frequency response, position error, temperature dependency, required output load and susceptibility to external magnetic fields.
- Weld time definitions: Standard defines “weld time” (cycles or milliseconds) and “current flow time” (for DC - time to decay to 10% of measured value). Annexes provide integrator/coils circuits, conversion coefficients and calibration details.
Applications and who uses it
ISO 17657-1 is intended for:
- Welding equipment manufacturers and suppliers of welding current meters and current sensing coils
- Quality/QA engineers in automotive, aerospace and heavy industry using resistance welding
- Calibration laboratories and test houses performing verification or calibration of welding current measuring systems
- R&D teams developing resistance welding controllers and metrology systems
Practical uses include selecting appropriate current sensors, ensuring traceable calibration, verifying weld current and weld time for process control, and reducing measurement uncertainty in production and testing.
Related standards
Keywords: ISO 17657-1, resistance welding, welding current measurement, current sensing coil, welding current meter, calibration, weld time, verification.
Open preview (PDF)Resistance welding — Welding current measurement for resistance welding — Part 1: Guidelines for measurement