Overview
ISO 17657-4:2005 - "Resistance welding - Welding current measurement for resistance welding - Part 4: Calibration system" defines calibration systems and procedures for measuring welding current in resistance welding. It covers calibration of welding current measuring systems, current sensors, welding current meters and monitoring devices for alternating current (50 Hz or 60 Hz) and direct current. The standard applies to currents from 0.5 kA to 25 kA and aims to ensure traceable, repeatable current measurement for quality control and process validation.
Key topics and technical requirements
- Scope and components: Calibration systems consist of a reference welding current measuring system (calibrated current sensor, data acquisition system and display/recorder), a test set-up (power source and secondary circuit) and the test welding current meter or sensor.
- Reference sensor: Requirements for reference sensors include high accuracy (measuring accuracy within ±0.5% including positioning error, or fixed positioning), and guidance for non‑inductive shunts (conversion coefficient 10 mV/kA to 150 mV/kA; error < ±0.25%; phase shift < 1° for a sinusoidal wave current at 10 kHz).
- Data acquisition (DAQ): DAQ devices shall use an ADC of 12-bit or higher, have at least two simultaneous-sampling channels, sample at ≥10 000 samples per second per channel, and input impedance >500 kΩ. Calibration of DAQ channels and gains must be documented.
- Calibration frequency and accuracy: Components of the reference measuring system shall be calibrated by certified reference equipment at least once a year. The total measuring accuracy of the reference system must meet the highly accurate class defined in ISO 17657-2.
- Test set-up and environment: Test set-ups must deliver at least four representative current values across the intended range; multi-turn secondary circuits may be used. Operating conditions without adverse effect: +5 °C to +40 °C, relative humidity up to 95%, altitude up to 1000 m.
- Reporting and traceability: The standard specifies required test report content (reference system ID and accuracy, test equipment make/model, sensor position, frequency, waveform, time of current application, etc.) and reference documentation to be retained.
Applications and users
Who uses ISO 17657-4:
- Calibration laboratories and metrology labs performing high-current calibrations
- Welding equipment manufacturers and R&D teams validating current measurement systems
- Quality assurance, production engineers and process control teams needing traceable welding current measurements
- Third‑party auditors and certification bodies evaluating resistance welding measurement systems
Practical uses:
- Calibrating welding current sensors/coils, welding current meters and monitoring devices
- Establishing traceable measurement chains for production and acceptance testing
- Ensuring accurate process monitoring and repeatability in resistance welding applications
Related standards
- ISO 17657-1 - Guidelines for measurement
- ISO 17657-2 - Welding current meter with current sensing coil
- ISO 17657-3 - Current sensing coil
- ISO 17657-5 - Verification of welding current measuring system
- ISO 669 - Resistance welding equipment - Mechanical and electrical requirements
Keywords: ISO 17657-4:2005, resistance welding, welding current measurement, calibration system, current sensor calibration, data acquisition, reference sensor, welding current meter.