Woodward 2301E, Инструкция по установке и эксплуатации, Страница: 21 / 182

Manual 26641 2301E Digital Control
Woodward 11
Shields and Grounding
An individual shield termination is provided at the terminal block for each of the
signals requiring shielding. All of the inputs having a shield pin should be wired
using shielded, twisted-pair wiring. The optimum exposed wire length beyond the
shield should be limited to 25 mm (1 inch); however, up to 75 mm (3 inches) may
be used.
Relay outputs, contact inputs, and power supply wiring do not normally require
shielding, but can be shielded if desired. Shields should terminate to chassis and
may be direct or share a shield pin except the AI or CAN shields.
The 2301E is designed for shield termination to earth ground at the control. If
intervening terminal blocks are used in routing a signal, the shield should be
continued through the terminal block. If shield grounding is desired at the
terminal block, it should be ac coupled to earth with a capacitor. All other shield
terminations except at the control (in the field) should be ac coupled to earth
through a capacitor. A 1000 pF, 500 V capacitor is typically sufficient, however
1
–10 nF, 500–1500 V may be used or needed, and 1000 pF (1 nF) 1000 V is
recommended. The intent is to provide a low impedance path to earth for the
shield at frequencies of 150 kHz and up. Multiple direct connections of a shield to
earth risk high levels of current to flow within the shield (exception, see note
below on cabinet installations).
Shields can be grounded at both ends (2301E and load) if the cable length is
sufficiently short (i.e., within a cabinet, less than about 10 m straight line between
the ground points) to prevent ground loop current in the shield.
Cabinet Installations: If the 2301E is installed in a cabinet, shielded
I/O can be terminated directly to the cabinet (earth ground) at the
entry/exit of the cabinet, as well as at the control (recommended).
Installation concerns associated with wiring in systems with other
devices are addressed in the electrical connections section.
Figure 2-1. Installation of Wiring into Terminal
LED System Status Indicators
The LED located between terminals 30 and 31 is a two colored LED. The
following provides the functions of the LED status:

LED Off = Power Off

LED Green = System On

LED Solid Red = I/O Lock

LED Flashing Red = Fault (This indicates a major problem and should be
returned to Woodward for service).