ThingMagic Micro Hardware - Manual (Page 102)

ElectroStatic Discharge (ESD) Considerations
A D I V I S I O N O F T R I M B L E
Appendix C: Environmental Considerations 97
What actually gets to the Micro is also strongly influenced by the antenna installation,
cabling, and grounding discussed above.
Use the mean operating time statistic before and after one or more of the changes
listed below to quantitatively determine if the change has resulted in an improvement.
Be sure to restart your statistics after the change.
Common Installation Best Practices
The following are common installation best practices which will ensure the readers isn’t
being unnecessarily exposed to ESD in even low risk environments. These should be
applied to all installations, full power or partial power, ESD or not:
Insure that Micro, Micro enclosing housing (e.g. Vega reader housing), and antenna
ground connection are all grounded to a common low impedance ground.
Verify R-TNC knurled threaded nuts are tight and stay tight. Don’t use a thread locking
compound that would compromise the grounding connection of the thread to thread
mate. If there is any indication that field vibration might cause the R-TNC to loosen,
apply RTV or other adhesive externally.
Use antenna cables with double shield outer conductors, or even full metallic shield
semirigid cables. ThingMagic specified cables are double shielded and adequate for
most applications. ESD discharge currents flowing ostensibly on the outer surface of
a single shield coaxial cable have been seen to couple to the inside of coaxial cables,
causing ESD failure. Avoid RG-58. Prefer RG-223.
Minimize ground loops in coaxial cable runs to antennas. Having the Micro and
antenna both tied to ground (per item 1) leads to the possibility of ground currents
flowing along antenna cables. The tendency of these currents to flow is related to the
area of the conceptual surface marked out by the antenna cable and the nearest
continuous ground surface. When this conceptual surface has minimum area, these
ground loop current are minimized. Routing antenna cables against grounded
metallic chassis parts helps minimize ground loop currents.
Keep the antenna radome in place. It provides significant ESD protection for the
metallic parts of the antenna, and protects the antenna from performance changes
due to environmental accumulation.
Keep careful track of serial numbers, operating life times, numbers of units operating.
You need this information to know that your mean operating life time is. Only with this
number will you be able to know if you have a failure problem in the first place, ESD
or otherwise. And then after any given change, whether things have improvement or
not. Or if the failures are confined to one instantiation, or distributed across your
population.