User's Guide

Review Copy 11-6-10
ThingMagic Micro Family User Guide
53
www.JADAKtech.com
Identifying ESD as the Cause of Damaged Readers
The following are some suggested methods to determine if ESD has caused reader failures, i.e., ESD
diagnostics. Some of these suggestions have the negative result experiment issue.
• Return failed units for analysis.
Analysis should determine if it is the power amplifier that has failed, but won’t be able to definitively
identify that the cause is ESD. However, ESD is one of the more common causes of PA failure.
• Measure ambient static levels with static meter, for example, AlphaLabs SVM2.
Note the static potentials floating detected. High static doesn’t mean discharges, but should be
considered cause for further investigation. High levels that keep changing are highly indicative of
discharges.
• Touch some things around the antenna and operating area.
If you feel static discharges, that is an indication of what is in front of the antenna. What 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 to 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:
• Ensure 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. 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 full metallic shield semi rigid cables. JADAK
specified cables are double shielded and adequate for most applications. ESD discharge currents
flowing on the outer surface of a single shield coaxial cable have coupled to the inside of coaxial cables,
causing ESD failure. Avoid RG-58. RG-223 is preferred.
• Minimize ground loops in coaxial cable runs to antennas. Tying both the Micro and antenna 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 currents 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 antenna’s metallic parts
and protects the antenna from performance changes due to environmental accumulation.
• Keep careful track of serial numbers, operating lifetimes, and numbers of units operating in order to
determine the mean operating lifetime. This number indicates if you have a failure problem, ESD or
otherwise. After any given change, it also indicates whether things have improved and if the failures are
confined to one instantiation or distributed across your population.