Grounding in lab.

fidel

Hi all. We're moving to a new lab and I need to have a reliable ground for ESD protection, e.g. connecting the ESD mat safely. My questions are: can I just use the ground in the power outlet, or I need to request a different ground? Do I need to connect a resistor between the mat and the ground?

berkeman

The mat should come with grounding instructions. Usually there will be a built-in resistor at the connection point, but you should check. You want a large value resistor (few hundred kOhm, I would think) to limit the current in the event of an electrocution hazard from equipment located above the mat.

The ground in an AC Mains socket should serve the purpose, once you've located the current limiting resistor.

mgb_phys

You can buy special plugs that only have an earth pin, contain a built in resistor and have the press-stud connector for a ground mat.

It's not especially important that the mat is grounded, just that your, wrist strap+bench mat+floor pad are connected together.
If you have an insulation tester or even an ohm meter it's worth checking the grounds of sockets in newly built labs are correctly earthed - it's amazing how many aren't, or have live/neutral swapped etc.

fidel

Well, to check the ground of the socket with an ohm meter, one probe to the "ground", how about another?

mgb_phys

Water pipe, ground outlet in another socket or if you are on the ground floor in a flower bed outside.

fidel

Got it! Thank you.

NoTime

The make a special plug for testing outlets.
Should be < $10 at almost any hardware store.
Validates power, ground, reversed wiring, and open connections.