Monday, January 10, 2005

Minimum voltage for electrostatic discharge?

Someone asked me today if there is a minimum voltage for required an electrostatic discharge (ESD) to happen. He was probably thinking of the Paschen minimum - this is a minimum voltage to break down an air gap between two electrical conductors. When two electrodes are brought closer together, the breakdown voltage between then reduces nearly linearly with distance. However a minimum occurs at about 0.1 mm - at this distance an air discharge requires about 300-350 V across the gap. If you bring the conductors closer, the breakdown voltage theoretically increases! In practice it may not, because a different type of discharge occurs at small gaps. So really there is no minimum - at the limit an ESD will occur when the conductors touch.

1 comment:

Steve Fowler said...

What many people mean about a minimum electrostatic discharge has something to do with their interest:
1. Minimum to feel - 3,000 - 3,500 Volts
2. Mimimum to feel pain - maybe 7,000 - 10,000 Volts (person and body part dependent)
3. Minimum to Ignite vapors - Usually over 1200- 1500 Volts
4. Minimum to damage electronics - 10 - 1,000's Volts ???????
5. Minimum to physically damage plastic - 100,000's Volts
6. Biologically Damaging to a person - depends on body entry point and exit point. 20,000 Volts may cause nerve damage where 3,000,000 Volts may only flash over.

Complicated Question!