16
P
B
= P
B
’ – P
Loss
Divide the result by the cable attenuation (Att) in dB/km to arrive at the maximum cable length. Note that the
transmitter output power data given in the specifications already includes connector loss when using precision
ceramic ST connectors.
Length = P
B
/ Att
7.1.2
Fiber Optic Connector
The fiber optic cables (or “patch cords”) used with the MJ-X
L
Fiber Optic Communications Module must be
terminated with ST style connectors and have a numerical aperture of 0.275 ± 0.015.
(If pre-terminated cables are not used, follow the instructions supplied by the manufacturer to attach the connector
to the fiber cable using the cable type recommended in section 7.1.)
7.1.3
Fiber Optic Connections
When making connections to the transmitter and receiver inputs/outputs, ensure that the transmit output from one
device is connected to the receive input of the next device. Figure 7-1 shows how to insert the connector. The tip of
the cable on the ST connector must be clean and free of dust. Dust on the tip of the cable will cause signal
attenuation.
Caution:
Use extreme care when handling the fiber optic connector, especially the exposed ceramic ferrule.
Figure 7-1 Fiber Optic Connections
7.2 RS-485 Twisted-pair Cable
The following sections provide the information necessary to select and install cable between an MJ-X
L
Control
Panel, RTU, and other field devices in an RS-485 network.
7.2.1
RS-485 Cable Type
Listed in Table 7-1 are the cable characteristics necessary for proper electrical performance in an RS-485
communications network. Use cable with a shield that provides 100 percent RFI/EMI coverage.
