I'm suspicious. Why are some resistances specified "+/-"? I'm pretty
sure it doesn't have a negative resistance. And the units of volume
resistivity are ohm-cm (or ohm-m), not ohm/cm.
The fact that it doesn't specify compliance to any industry standard
also is a concern. An anti-static mat should comply with "ANSI/ESD
S4.1" or "ANSI/ESD S20.20". Those standards specify measuring the
resistance between two weighted, circular electrodes of a certain size
and spaced a certain distance apart on the mat. The resistance should
measure between 1 Mohm and 1 Gohm, depending on the relative humidity.
Here are the results of some testing I did on anti-static mats a few
years ago, along with a recommendation for one mat I found that did
measure within spec:
http://www.mail-archive.com/elecraft%40mailman.qth.net/msg94407.html
The bottom line is, many so-called "anti-static" mats don't do the job.
And the problem is, there is no easy way to tell. Just because you
managed to build something without damaging any parts doesn't prove the
mat is working correctly. This is one area where it doesn't pay to go
cheap.
Alan N1AL
On 04/17/2016 01:24 PM, Bruce Nourish wrote:
Hi folks,
I'm adding a 2m unit to my factory built KX3, and wanted to check if the
specs on this mat were adequate:
http://www.velleman.eu/products/view/?country=be&lang=en&id=382422
surface resistance: ± 10^8 - 10^10 Ω/sq
volume resistance: < 10^10 Ω/cm
RTT (point to point): ± 10^8 - 10^10 Ω
It includes a wrist strap with a 1 MΩ resistor. The numbers look to be in
the ball park of the examples given in the KX3 manual, but I wanted to
check before I started poking around the guts of my very expensive toy.
Bruce
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