See 7.2.4.1 of the standard ( my bold text):

Rationale: Ungrounded equipment, or*ungrounded part(s) of equipment,* cannot discharge itself similarly to class I mains-supplied equipment. If the charge is not removed before the next ESD pulse is applied, it is possible that the EUT or part(s) of the EUT be stressed up to twice the intended test voltage. Therefore, this type of equipment or equipment parts could be charged at an unrealistically high charge, by accumulating several ESD discharges on the capacitance of the class II insulation, and then discharge at the breakdown voltage of the
insulation with a much higher energy.

Best wishes
John Woodgate OOO-Own Opinions Only
www.woodjohn.uk
Rayleigh, Essex UK

On 2020-03-12 15:53, Elliott Martinson wrote:

Hi Everybody,

We’re having some disagreements regarding the 61000-4-2 standard. In the section “ungrounded equipment”, it states that ungrounded equipment or part(s) of equipment shall have the charge removed in between ESD pulses in order to not over-test.

We have a product that only fails pre-compliance when repeated ESD pulses are applied to a floating metal knob without removing the charge in between (eventually there is a second discharge between the knob and the enclosure). The product as a whole is “grounded equipment”.

Since the issue only happens when the charge isn’t removed in between pulses, is this a pass or a fail?

Thanks,

Elliott Martinson

Controls Engineer

Sub-Zero/Wolf

elliott.martin...@subzero.com

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