Table of Contents
Advertisement
Electromagnetic Compatibility (EMC)
The various confi gurations of the Heater should not produce, or fall victim to, electromag-
netic disturbances as specifi ed in the European Union's EMC Directive. Strict compliance
to the EMC Directive requires that certain installation techniques and wiring practices
are used to prevent or minimize erratic behavior of the Heater or its electronic neighbors.
Below are examples of the techniques and wiring practices to be followed.
In meeting the EMC requirements , the various Heater confi gurations described in this
manual rely heavily on the use of metallic shielded cables used to connect to the custom-
er's equipment and power. Foil and braid shielded I/O and DC power cables are recom-
mended for use in otherwise unprotected situations. In addition, hard conduit, fl exible
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 treat-
ed on a case-by-case basis. Disconnecting one shield ground may not provide suffi cient
protection depending on the electronic environment. Connecting one shield ground via a
0.1 microfarad ceramic 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. In-
stall 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 disturbanc-
es, do not allow installation of this Heater where its unshielded I/O and DC circuits are
physically mixed with AC mains or any other circuit that could induce transients into the
Heater or the overall system. Examples of electrical events and devices known for the gen-
eration of harmful electromagnetic disturbances include motors, capacitor bank switching,
storm related transients, RF welding equipment, static, and walkie-talkies.
8 | Model ta3000R Gas Purity Monitor
Read and follow the recommendations in this section to avoid perfor-
mance variations or damage to the internal circuits of this equipment
!
when installed in harsh electrical environments.
CAUTION
Advertisement
Table of Contents
