B&B Electronics 516TX-A - Manual - Manual (Page 12)

(Revised 8/4/2009) 12
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. Please note that the minimum cross-
sectional area of the grounding conductor must be at least 4mm2
and it must be suitable for use in temperature of 110°C.
Note: Ensure the power supply is grounded properly before applying
power to the grounded switch. This may be verified by using a
voltmeter to determine that there is no voltage difference between the
power supply’s negative output terminal and the chassis grounding
point of the switch.
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.