SparkFun Forums

[qwertymodo]

I've been wanting an anti-ESD for my workbench for awhile now, but the cost has been prohibitive. Finally, I found one on AliExpress for $25 and figured even if I got exactly what I paid for, at that price it was worth a shot. I got it today, and one thing I've found strange is that the "top" green layer measures Hi-Z on my multimeter, regardless of your close the multimeter probes are. The *bottom* side, however, measures a resistance of 1-3MOhms, which is what I expected to see on the top layer. Am I incorrect in my assumption that the top layer should register a resistance across it instead of insulating like I'm seeing, or should I just flip the mat and use the "bottom" side as my work surface?

[cristoper]

The top layer should be dissipative, but non-conductive. Usually that means greater than 10^6 but less than 10^9 ohms. The bottom layer should be conductive, anywhere from 10^3 to 10^6 ohms. So your measurements look normal. I expect your readings are a bit high because you are simply measuring with your probe tips. If you instead use a larger conductor (a coin even) and press it against the surface as a measurement point, I bet you would find the bottom layer to be under a megaohm per square.

[qwertymodo]

Ok, that's good to know. My only experience was one of Dave Jones' EEVBlog videos where he showed off his anti-static mat and measured a ~Mohm resistance across its top surface with just his DMM probes. But yesterday, I went into my school's EE lab and tried it on their anti-static mats, and they behaved the same as mine. So all seems well.