ESD Simulator design?

[ftransform]

How do these devices work? Why do they cost 4000$?
I assume its more of a niche market gotta pay the engineers thing vs a cost of parts thing.

What is in these magical boxes?

[Short Circuit]

An adjustable PSU 1-15kV (or even up to 25kV), a resistor, a capacitor, high voltage relay to discharge, and some probes with specificallty defined geometry.
Indeed price is for a large amound due to R&D costs, and extensive quality control, tracability, calibration etc.

And partially because they can (I think), works as long as all manufacturers play along and stay roughly in the same pricerange.
No really a problem, because their customers are mostly EMC laboratories, for which even the most expensive ESD gun is still
among the cheapest bits of gear.

[ftransform]

Why is the probe geometry so important?

[Short Circuit]

Because EN 61000-4-2-2009  says so 

[free_electron]

low volume production is the reason.

The guts of these things are pretty simple. adjustable high voltage source , charging circuitry , a 'model' and a high voltage mercury wetted relay.

You don't need a lot of current from that source, just enough to charge the 'model'.
The relay is critical. it needs to be absolutely bounce free : shoot it closed and it needs to stay closed without bounce. the energy from the model needs to discharge in 1 shot.

the 'model' is a reference circuit made out of 1 capacitor and 1 resistor. we charge the capacitor from the hv source , then disconnect the hv source. the capacitor is discharged through the resistor and relay contact into the structure to be tested.

There are a number of 'models' . human body model , machine model and others. these 'models' actually define pulse shapes. with a maximum voltage applied.

advanced esd zappers allow you to select the model and they switch resistors and caps internally.

the 'old-skool' zappers had a cartridge containing the right parts that would simply be plugged in. you could then test against taht model and onyl had one knob to adjust the voltage of the pulse. another button allowed to select pulse repitition.


some lecture : http://www-tcad.stanford.edu/tcad/pubs/theses/sbeebe.pdf

[Neilm]

The ESD tests consists of 2 types of test - the air discharge test and the contact discharge test. The first one is reasonably easy, charge up the test probe (size and shape specified by the standard) to the correct voltage and bring it close to the UUT. The second one you have to touch the UUT with the tip then trigger the test.

The probe has to be built so that the discharges it does are repeatable and meet the standard waveforms (which I can't remember)

The probe tip is important as it will influence the way the discharge happens, obviously a point will concentrate the charge leading to it discharging from that tip which might not be what was required.

Yours

Neil