PN T900-014, Rev B
Electromagnetic Compatibility (EMC)
Read and follow the recommendations in this section to avoid performance
variations or damage to the internal circuits of this equipment when installed
in harsh electrical environments.
The various configurations of the ta7000F should not produce, or fall victim to, electromagnetic
disturbances as specified in the European Union’s EMC Directive. Strict compliance to the EMC Direc-
tive requires that certain installation techniques and wiring practices are used to prevent or minimize
erratic behavior of the ta7000F or its electronic neighbors. Below are examples of the techniques and
wiring practices to be followed.
In meeting the EMC requirements, the various ta7000F configurations described in this manual rely
heavily on the use of metallic shielded cables used to connect to the customer’s equipment and pow-
er. Foil and braid shielded I/O and DC power cables are recommended for use in otherwise unprotect-
ed situations. In addition, hard conduit, flexible conduit, and armor around non-shielded wiring also
provides excellent control of radio frequency disturbances. However, use of these shielding techniques
is effective only when the shielding element is connected to the equipment chassis/earth ground
at both ends of the cable run. This may cause ground loop problems in some cases. These should be
treated on a case-by-case basis. Disconnecting one shield ground may not provide sufficient protec-
tion depending on the electronic environment. Connecting one shield ground via a 0.1 microfarad ce-
ramic capacitor is a technique allowing high frequency shield bonding while avoiding the AC-ground
metal connection. In the case of shielded cables the drain wire or braid connection must be kept short.
A two-inch connection distance between the shield’s end and the nearest grounded chassis point,
ground bar or terminal is highly recommended. An even greater degree of shield performance can
be achieved by using metallic glands for shielded cable entry into metal enclosures. Expose enough
of the braid/foil/drain where it passes through the gland so that the shield materials can be wrapped
backwards onto the cable jacket and captured inside the gland, and tightened up against the metal
interior.
Inductive loads connected to the low voltage “Alarm Contacts” are not recommended. However, if
this becomes a necessity, adhere to proper techniques and wiring practices. Install an appropriate
transient voltage suppression device (low voltage MOV, “Transzorb,” or R/C) as close as possible to the
inductive device to reduce the generation of transients. Do not run this type of signal wiring along
with other I/O or DC in the same shielded cable. Inductive load wiring must be separated from other
circuits in conduit by using an additional cable shield on the offending cable.
In general, for optimum protection against high frequency transients and other disturbances, do not
allow installation of the ta7000F where its unshielded I/O and DC circuits are physically mixed with AC
mains or any other circuit that could induce transients into the ta7000F or the overall system. Exam-
ples of electrical events and devices known for the generation of harmful electromagnetic disturbanc-
es include motors, capacitor bank switching, storm related transients, RF welding equipment, static,
and walkie talkies.
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