Is a Wrist Strap Enough for ESD Protection Without Grounded Mats?

[likephysics]

Can you claim to have ESD protection if you have just the wrist strap connected to ground and not the ESD mats on a typical workbench?

With just the wrist strap, ESD is instantly discharged to ground. With the ESD mat, the charge is gradually discharged to ground.

 

[the_emi_guy]

Wrist straps are never connected directly to ground. Typically a 1Meg ohm resistor should be in series.

A static dissipative work surface is necessary on a typical workbench.

 

[likephysics]

A static dissipative work surface is necessary on a typical workbench.

Why exactly do you need the static dissipative work surface.

 

[davenn]

Can you claim to have ESD protection if you have just the wrist strap connected to ground and not the ESD mats on a typical workbench?

definately not

With just the wrist strap, ESD is instantly discharged to ground. With the ESD mat, the charge is gradually discharged to ground.

wrist straps DONT instantly discharge to ground ( well not in the way you are probably thinking
as said by the_emi_guy ... they are not connected directly to ground. that would present the wearer of the strap with the potential of being electrocuted

The wrist strap, like the mat, are high resistance to ground

Why exactly do you need the static dissipative work surface.

so that you and the equip you are working on are BOTH static grounded

cheers
Dave

 

[Averagesupernova]

The wrist strap is always connected to ground. Usually through a resistor as has been stated. The static mat is similarly connected.
-
ESD mats behave a little differently than one might expect. Take your ohmmeter probes and stab them into the mat and you will be hard pressed to get a reading. But, take two wet sponges and lay on the mat a short distance apart and then stab the ohmmeter probes into the sponges. You will definitely find a low enough of an impedance to drain away ESD charges. I have found if you have a wooden surface on the bench that has gotten soiled with use makes a pretty good ESD mat all by itself. This assumes it is mounted to something that is grounded.

 

[likephysics]

The wrist strap is always connected to ground. Usually through a resistor as has been stated. The static mat is similarly connected.
-
ESD mats behave a little differently than one might expect. Take your ohmmeter probes and stab them into the mat and you will be hard pressed to get a reading. But, take two wet sponges and lay on the mat a short distance apart and then stab the ohmmeter probes into the sponges. You will definitely find a low enough of an impedance to drain away ESD charges. I have found if you have a wooden surface on the bench that has gotten soiled with use makes a pretty good ESD mat all by itself. This assumes it is mounted to something that is grounded.

The sponge experiment, I will definitely do.

I guess without the mat, a regular surface might be a source for picking up static, like when you wipe it with a piece of cloth or when your sweater rubs against the surface?

 

[likephysics]

Another ESD related question - I have seem some tables with ESD mats wired to a metal ball at the bottom of the table, lying on the ground.
Is the ball used as ground instead of connecting to real Earth.

 

[Averagesupernova]

I would assume the ball contacting the floor is considered a good enough ground to protect against ESD.