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[SOLVED] ESD Circuit protection against electrostatic painting

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asraralam123

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I have a circuit for an automotive sensor aimed for 24V supply. The circuit itself is well tested for EMC requirements including power line transients and EMC immunity. Usually the requirement is for all the terminal pins to be galvanically isolated from the metal housing. We have but a strange requirement from one of our customers that demands the opposite. They subject our sensors to electrostatic painting and it may be - just may be- that some charge gets induced on one of the terminal pins. They want some high resistance conduction path from the pins to the case-housing to provide as a relief valve for the charge to be grounded in such situation. I already have the Y-caps from case-housing to all the lines. I was thinking of some high resistors in parallel to each of these caps as a charge draining path. but then what effect would it have on the galvanic insulation requirement (>10Meg @ 500V)?
 

10 Mohm is relative low in terms of ESD protection. Why not use e.g. a 100 Mohm resistor? I presume, there's already a conductive path between terminals, hence a single resistor would be sufficient.
 
You would think that powder-coating the terminals would be bad,
ESD or no.

Maybe an answer would be using a conductive-material connector
"filler plug" which could at least short the pins (case-to-guts charge
would not be helped). Many sensors come with some sort of plug
to protect the pins from handling / shipping damage or corrosion in
storage. This would go away on installation so you don't have a
care about degrading your isolation spec. A clever mechanical
design might also include a tab that contacts the case "just enough"
to bleed charge, but not enough to bother the paint job?

Or maybe the customer / paint shop makes that all part of the
spray booth fixture "target mount" and solves their own problem.
 

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