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Testing if supplementary bonding is required.

MrJack96
I have read some bits stating we can measure between the two metallic parts in question and referring to the formula 


50/ia will give you the resistance needed to keep touch voltage to less than 50v 


my questions can we do the same test to determine if the part has a high enough resistance to not require bonding and what sort of figures we should look for?
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    Certainly can. You have to pick an maximum acceptable body current - often 10mA is chosen from purely a avoiding death by electric shock point of view (but some designers might prefer lower figures especially for wet areas or where the result of a non-fatal shock might still be fatal - e.g. falling from a height).


    The maximum voltage is likely to be around full mains voltage - say 230V - so it's just them Ohm's law for a resistance to keep the current low enough - so say 230V/0.01A = 23k Ohms. Some subtract a likely body resistance from that (say 1kΩ) but not bothering errs on the side of safety.


    Similarly if you picked 1mA and thought you might have 250V rather than 230V to worry about, you'd end up with 250kΩ.


       - Andy.
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  • 0
    Certainly can. You have to pick an maximum acceptable body current - often 10mA is chosen from purely a avoiding death by electric shock point of view (but some designers might prefer lower figures especially for wet areas or where the result of a non-fatal shock might still be fatal - e.g. falling from a height).


    The maximum voltage is likely to be around full mains voltage - say 230V - so it's just them Ohm's law for a resistance to keep the current low enough - so say 230V/0.01A = 23k Ohms. Some subtract a likely body resistance from that (say 1kΩ) but not bothering errs on the side of safety.


    Similarly if you picked 1mA and thought you might have 250V rather than 230V to worry about, you'd end up with 250kΩ.


       - Andy.
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