Overview
ISO 17657-2:2005 specifies requirements for a welding current meter with a current sensing coil used in resistance welding. The standard defines how to measure weld time and the r.m.s. value of welding current for single-phase alternating current (50 Hz or 60 Hz) and direct current. It applies to welding current measuring systems with a display or calibrated output port that may be connected to welding controllers for process control and quality assurance.
Key topics and technical requirements
- Scope and environment
- Operability at ambient temperatures of +5 °C to +40 °C, relative humidity up to 95%, and altitudes up to 1 000 m; tolerance to common welding atmospheres (dust, oil mist, spatters).
- Measurement capability
- Measures true r.m.s. welding current and indicated measuring time (start/finish time logic for weld-time windows).
- Supports single-phase AC (50/60 Hz) and DC; cycle-based timing for AC and millisecond timing options for DC.
- Accuracy and classification
- Welding current meter with current sensing coil (system) classified by accuracy:
- Highly accurate: ±1.0% of full scale (laboratory use)
- Accurate: ±2.0% of full scale (routine high-accuracy systems)
- Ordinary: ±5.0% of full scale (routine systems)
- Welding current meters alone have tighter meter-only classes (e.g., highly accurate ±0.5% of full scale).
- Components and functionality
- Current sensing coil must conform to ISO 17657-3 and match integrator conversion coefficients.
- Integrator must process full-wave and heat-controlled AC without clipping/distortion.
- Data processing unit: ADC, memory, CPU; algorithm must compute true r.m.s. values and store results until next measurement.
- Display and outputs: pointer, digital or print-out displays for current and weld time; analog/digital output ports for waveform and data.
- Testing, calibration and verification
- Type and acceptance testing procedures and thermal tests are required (see Clauses 6–7).
- Calibration and verification should follow ISO 17657-4 (calibration system) and ISO 17657-5 (verification).
Applications and users
- Who uses it
- Welding equipment manufacturers, process engineers, QA/QC personnel, calibration laboratories, and research/testing laboratories.
- Practical applications
- Process control and monitoring of resistance welding (spot and projection welding).
- Verification and calibration of welding controllers and current sensing coils.
- Ensuring repeatable weld quality and traceable measurements for production and laboratory environments.
Related standards
Keywords: ISO 17657-2:2005, welding current meter, current sensing coil, resistance welding, weld time, r.m.s. value, welding current measurement, measurement accuracy, integrator, calibration.
Open preview (PDF)Resistance welding — Welding current measurement for resistance welding — Part 2: Welding current meter with current sensing coil
