esd
How do ESD monitors work? Especially those dealing with one wired ESD wrist band. All I've been able to grasp is that the human body acts as a capacitor between the wrist band and the ground. But I don't understand how you can detect if an operator is wearing the wrist band or not. Should you run a current through him?
If anyone knows the answer a detailed explanation would be very appreciated.
Most controlled test would be to use a human model like this:
For the high voltage supply I would use a Cockcroft Walton voltage multiplier with an isolation transformer. For 220V mains, you'll need 9 stages.
(source: eet.com)
My go to method is my ghetto ESD-gun (a cheap electronic lighter) ala - Long neck lighter Split it open, strip the wires and zap away :) It should produce a few kilo volts.
Best Answer
An ESD monitor or ESD tester like this:
is like a crude resistance meter.
ESD (Electro Static Discharge) events are caused by charge that is trapped. This charge will try to find its way to ground as soon as it can. This might be through a sensitive device which can be damaged.
To prevent that damage we have to make sure that no charge buildup can take place. That is done by connecting everything to ground including humans. The connection doesn't need to be very low ohmic (have a low resistance), even if there's a 1 M ohm resistor in series between the human and ground, that will still work.
Actually having some resistance in place between the human and ground is preferred as that prevents a large current from flowing when the human accidentally touches a mains live connection. Would you like to touch 240 V AC while your other hand is directly grounded? Neither would I but if the ground connection has 1 Mohm in series it becomes a lot safer.
That's that the ESD test station tests. It measures the resistance between your body (you need to touch a metal pad with your finger) and ground. If you're properly grounded with a safe 1 Mohm ESD wristband the test station will indicate everything is OK. If no connection at all is measured then you will fail the test.
So: an ESD monitor/tester measures the resistance between your body and ground.