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To ground or not?

I have designed a battery operated system which is installed inside a sheet metal enclosure. The systems are used outdoors and are often mounted near equipment associated with utilities (phone, CATV, etc). As it is now, I have all PCBs mounted to the enclosure in a non-isolated manner. My mounting (screw) holes are plated and tied to the reference node (gnd) on my PCBs. The standoffs are metallic and so are the screws. So, there exists a conductive path (< 1 ohm) from ground on the board to the chassis.

I did this without much thought... and now I am thinking it might not have been a wise choice. Any comments?

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Reply to
eeboy
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For battery powered kit I always isolate the board from the chassis..

I would then use one or more low ESR low ESL caps to connect between the circuit ground and the chassis ground to give a good EMC ground for the board.

Reply to
Raveninghorde

That's the best way to do it; ground hard and often to the metal enclosure. For lightning protection, all wires that exit the box should be protected by serious transient supressors. Lightning protection is non-trivial for things like this.

John

Reply to
John Larkin

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Therde are three ways to handle this kind of equipment.

  1. Ground everywhere.
  2. Ground at one point.
  3. Completely isolate internal circuits.

All three are correct in certain applications. In some applications, more than one method will be "correct".

Reply to
Richard Henry

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