Radio Shack FX2 User Manual download pdf (Page 12)

Revision 050908 Page 12 of 101

N-TRON SWITCH GROUNDING TECHNIQUES

The grounding philosophy of any control system is an integral part of the design. N-Tron switches are

designed to be grounded, but the user has been given the flexibility to float the switch when required. The

best noise immunity and emissions (i.e. CE) are obtained when the N-Tron switch chassis is connected to

earth ground via a drain wire. Some N-Tron switches have metal din-rail brackets that can ground the

switch if the din-rail is grounded. In some cases, N-Tron switches with metal brackets can be supplied with

optional plastic brackets if isolation is required.

Both V- legs of the power input connector are connected

to chassis internally on the PCB. Connecting a drain wire

to earth ground from one of the V- terminal plugs as

shown here will ground the switch and the chassis. The

power leads from the power source should be limited to 3

meters or less in length.

As an alternate, users can run a drain wire & lug from any of the

Din-Rail screws or empty PEM nuts on the enclosure. When

using an unused PEM nut to connect a ground lug via a machine

screw, care should be taken to limit the penetration of the outer

skin by less than 1/4 in. Failure to do so may cause irreversible

damage to the internal components of the switch.

Note: Before applying power to the grounded switch, you must

use a volt meter to verify there is no voltage difference between

the power supply’s negative output terminal and the switch

chassis grounding point.

If the use of shielded cables is required, it is generally recommended to only connect the shield at one end to

prevent ground loops and interfere with low level signals (i.e. thermocouples, RTD, etc.). Cat5e cables

manufactured to EIA-568A or 568B specifications are required for use with N-Tron Switches.

In the event all Cat5e patch cable distances are small (i.e. All Ethernet devices are located the same local

cabinet and/or referenced to the same earth ground), it is permissible to use fully shielded cables terminated

to chassis ground at both ends in systems void of low level analog signals.

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Radio Shack FX2 User Manual Page 12