IEC 61000-4-2 ESD Calibration Target for ESD Generator Verification

An ESD generator may correctly display a selected test voltage such as 2 kV, 4 kV or 8 kV, but that indication alone does not confirm that the actual discharge-current waveform is correct.

For reliable electrostatic discharge immunity testing, the output of the ESD generator must be characterized through a suitable current measurement system.

The ESD Calibration Target provides the interface required for this measurement.

During verification, the ESD generator is discharged directly onto the target. The resulting current pulse is converted into an electrical signal and transferred through an attenuator and coaxial cable to a high-bandwidth oscilloscope.

The oscilloscope waveform can then be used to evaluate the main characteristics of the discharge pulse, including the initial current peak, rise time and current values at defined time points.

The ESD Calibration Target uses a 2 Ω ±5% measuring resistor, supports ESD test voltages up to ±30 kV, and provides defined insertion-loss performance for the complete target–attenuator–cable measurement chain.

IEC 61000-4-2 establishes a reproducible method for evaluating the immunity of electrical and electronic equipment to electrostatic discharge.

A complete ESD immunity test depends not only on the DUT and selected test voltage, but also on whether the ESD generator produces the intended discharge waveform.

The current IEC edition, IEC 61000-4-2:2025, continues to address the ideal discharge-current waveform, test equipment, test setup and calibration of the current measurement system.

In practical laboratory work, this means that an ESD generator should not be judged only by the voltage displayed on its front panel.

Its actual discharge-current waveform must also be checked.

These four waveform characteristics are used to evaluate whether the ESD generator produces the required discharge-current pulse.

For laboratories, this verification helps distinguish a DUT failure from a possible problem with the ESD generator or measurement setup.

The measurement principle is straightforward:

When the ESD generator discharges onto the target, the current passes through the target’s measuring element.

The target converts the discharge current into a corresponding voltage signal. Because the ESD pulse is both fast and relatively high in amplitude, the output is passed through an attenuator before reaching the oscilloscope.

The oscilloscope then captures the waveform so that the required current characteristics can be evaluated.

Relationship Between Discharge Current and Measured Voltage

For this measurement configuration:

• Ip = discharge current in amperes
• Vm = voltage measured by the oscilloscope in volts

For example, a discharge current of 7.5 A corresponds to an oscilloscope reading of approximately 1.5 V under the specified 2 Ω target and 20 dB attenuation arrangement.

This relationship applies to the defined measurement chain. If the target, attenuation or connection arrangement changes, the conversion relationship should be verified accordingly.

The Complete Target–Attenuator–Cable Measurement Chain

A technically important point is that the current target should not be considered independently from the rest of the RF measurement path.

The specified insertion-loss performance applies to the complete:

Target + Attenuator + Cable chain.

Insertion loss is evaluated for the complete Target–Attenuator–Cable chain rather than for the target alone.

This matters in actual laboratory use.

Changing the cable, attenuator or connector arrangement may change the frequency response of the measurement system and therefore affect the captured ESD waveform.

For calibration or traceable verification work, laboratories should therefore define and maintain the complete measurement chain.

The ESD calibration target is one component of the complete verification setup. It is not a standalone automatic ESD calibration system.

The target is installed in the wall of a shielded room or in a conductive metal plate of at least 1.2 m × 1.2 m.

The physical arrangement of the ESD generator is also important.

The ground-return cable should be positioned carefully because its geometry can significantly affect the measured waveform, particularly the current readings at 30 ns and 60 ns. Incorrect routing may introduce oscillations that distort the observed pulse.

This is why ESD waveform verification should be treated as a complete measurement setup rather than simply connecting a target to an oscilloscope.

The optional 50 Ω conical adapter serves a different purpose from the ESD current target.

The current target is used when measuring the discharge produced by the ESD generator.

The 50 Ω conical adapter is used when verifying the RF characteristics of the current-target measurement system.

It provides a transition between a 50 Ω coaxial measurement connection and the geometry of the current target.

When two adapter lines are mounted face-to-face, the verification configuration provides:

• reflection coefficient better than 30 dB up to 1 GHz;
• reflection coefficient better than 20 dB up to 4 GHz;
• insertion loss below 0.3 dB in the stated configuration.

Current Target vs. Verification Adapter

The conical adapter therefore does not need to be treated as a separate ESD test instrument. It is an optional verification accessory for the current target.