Q&A Electrostatic Discharge Simulators

 Waveform measurement

 

Q1.

Why an ESD target is used to measure the discharge current waveform from ESD generators?

 

Q2.

What test instrument and accessories are required to measure the output waveform from an ESD generator?

 

Q3.

For calibration of ESD generator, the IEC 61000-4-2 standard says the generator (discharge gun) should be installed on a tripod or equivalent non metal low loss support but the ISO 10605 does not say anything about this. Can I hold the gun in my hand?

 

Q4.

Why does the IEC61000-4-2 define the discharge current waveform for contact discharge only, but not air discharge?

 

Q1.

Why an ESD target is used to measure the discharge current waveform from ESD generators?

 

   

ESD pulse waveforms (such as defined in the IEC 61000-4-2 standard) cannot be directly measured with any measurement instrument (oscilloscope) due to their high voltage and fast properties. 

 

The ESD target, the electrical and mechanical specifications are defined in the standard, is a kind of transducer from current to voltage by means of a low impedance with characterized frequency response over a specified range, allowing an appropriate scope to measure the voltage across the resistance (typically 2 ohm) of the ESD target.  Also refer to Q&A No.2.

   
Q2.

What test instrument and accessories are required to measure the output waveform from an ESD generator?

 

   

The following equipment and accessories are required:

  • 06-00067A ESD current target   
  • 00-00011A 20dB attenuator
  • 02-000132A coaxial cable
  • 00-00010A 6dB attenuator (1 piece or 2 pieces depending on test voltage
  • 02-00133A coaxial conversion SMA to BNC, when your scope input is a BNC type)  
  • Oscilloscope with >2GHz bandwidth for IEC 61000-4-2 or >1GHz bandwidth for ISO 10605

 

The ESD current target shall be mounted on a metal plate working as a shielding wall (03-00052B 1.2 x 1.2 m, specifically designed for this purpose, also available) and the scope shall be placed to the output side of the target to be electromagnetically separated from the ESD generator.

 

All the said items shall be connected in the following order to form an ESD target-attenuator-calibration chain: 06-00067A ESD current target -00-00011A 20dBattenuator - 02-000132A coaxial cable - 00-00010A 6dB attenuator (1 piece or 2 pieces depending on test voltage)    

 

The following options make easy for you to create the conditions required in the IEC/ISO standards.

  • 03-00060A Cable Positioner

The discharge return cable shall be connected to the plane onto which an ESD current target is installed at a distance of 0.5m below the ESD current target and shall be pulled backwards at its midpoint to form an isosceles triangle.

  • 03-00061B Discharge Gun Mount

This mount is attached to the 03-00052B plane and holds the discharge gun. 

   
Q3.

For calibration of ESD generator, the IEC 61000-4-2 standard says the generator (discharge gun) should be installed on a tripod or equivalent non metal low loss support but the ISO 10605 does not say anything about this.  Can I hold the gun in my hand?

 

   

Our company's understanding on this issue is the IEC method is the preferred way, minimizing the affects on the waveform due to user-to-user variations.

   
Q4.

Why does the IEC 61000-4-2 define the discharge current waveform for contact discharge only, but not air discharge?

 

   

Air discharges are inherently unstable events. One major difference from contact discharge is the factor of discharge arc, the length of which varies depending on test voltage.  This discharge arc path in some part accounts for variable rise times and peak amplitudes, which in reality make air discharge waveform parameters too complicated to define.

 

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