Overview
EN ISO 17657-2:2007 / ISO 17657-2:2005 defines requirements for a welding current meter with a current sensing coil used in resistance welding. The standard specifies how to measure weld time and the true r.m.s. value of welding current for single‑phase alternating current (50 Hz or 60 Hz) and direct current (DC). It applies to systems with a display or calibrated output port that may interface with welding controllers and quality systems.
Key topics and technical requirements
- Measured quantities: true r.m.s. welding current and indicated measuring time (start/finish interval while current flows).
- Current types supported: single‑phase AC (50/60 Hz) and DC.
- Accuracy classes:
- Highly accurate class: ±1.0% of full scale (laboratory use)
- Accurate class: ±2.0% of full scale (routine use for high‑accuracy systems)
- Ordinary class: ±5.0% of full scale (routine use)
- System components: data processing unit, integrator, display unit and output ports, and the current sensing coil.
- Operating conditions: designed to operate without accuracy loss at +5 °C to +40 °C, relative humidity up to 95%, and altitudes up to 1 000 m; tolerance to typical welding environment contaminants (gas, dust, oil mist, spatters).
- Performance and safety aspects covered: minimum/maximum measuring time, minimum/maximum measurable current, phase‑controlled current handling, minimum time resolution, fluctuation of supply voltage, mechanical strength and setting‑position error of the sensing coil, temperature influence and drift (automatic zero level correction).
- Testing: type tests and acceptance tests are specified for verification of performance.
Practical applications and users
- Who uses this standard: welding equipment manufacturers, welding process engineers, quality assurance and inspection teams, calibration laboratories, and research & development groups working with resistance welding.
- Why it matters: ensures consistent, traceable measurement of welding current and weld time - critical for process control, repeatability, joint quality, and compliance with production and safety specifications.
- Typical use cases: integration of current meters into welding controllers for process monitoring and logging; laboratory verification of weld schedules; factory acceptance testing and routine production checks.
Related standards
- ISO 17657-1: Guidelines for measurement
- ISO 17657-3: Current sensing coil
- ISO 17657-4: Calibration system
- ISO 17657-5: Verification of welding current measuring system
- ISO 669: Resistance welding equipment - mechanical and electrical requirements
- Adopted as EN ISO 17657-2:2007 by CEN (European national standard implementation)
Keywords: resistance welding, welding current meter, current sensing coil, ISO 17657-2, r.m.s. welding current, weld time measurement, measurement accuracy, calibration, welding process control.
