Siemens MJ-X, Руководство по установке

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MJ-X
L
Communications Module
15
2. Press the Change key, then the up arrow key to select “LOOPBK.” If the password is requested, enter the
password and proceed.
3. Press the Save key. It should display “LOOPBK” for several seconds before changing automatically to “OFF.”
If this does not occur, then recheck the physical installation of the communications module and retry.
4. Once the “CM Test:?” screen displays “OFF,” press the down arrow key to display the “CM TestStat” data
item. This screen gives the status of the communications module test. A value of xxx7 (where x may be 0-9 or
a-f), indicates that the loopback test passed. A value of xxx0 - xxx6 indicates a failure.
•
xxx0 indicates the test did not run at all. Run the test again, allowing extra time for the communications
module to power up. This should take about 15 seconds. The Watchdog LED will blink after the module
successfully completes self test and initialization.
•
xxx1 or xxx2 indicate an internal problem with the MJ-X
L
Communications Module. Contact Siemens for
assistance.
•
xxx3 indicates the loopback test failed. Check the loopback connectors and repeat the test.
•
xxx4 , xxx5 , or xxx6 indicates a communication problem. Contact Siemens for assistance.
7 Cabling the Communications Module to the Power System
Connect the communications modules using the recommended cable as described in sections 7.1 to 7.3 below. The
following sections provide some general guidelines for cable selection and explain the different cable parameters.
Make connections between the device and the communications unit with the appropriate connector.
Typically, RS-485 requires custom wiring to the other devices. Consult the device’s pin assignments to determine
the applicable connections. Typically, a DE-9 or DB-25 will be needed for making RS-232 connections to the RTU,
personal computer, or other device. Use the supplied Phoenix Contact Screw Terminal Block (MSTBT 2,5/8-ST-
5,08) for connections to the RS-232/485 module. Use an ST optical connector when making connections to the
fiber optic module.
7.1 Fiber Optic Cable Type
The recommended cable is 62.5/125
µ
m diameter fiber optic cable with a maximum attenuation of 5dB/km at a
wavelength of 820-850 nm. If this is not available use 50/125
µ
m diameter glass cable, but only for cable lengths
less than 1500 feet. Use of 50/125
µ
m diameter cable requires that the range jumper J607 be set for long range.
This will provide protection against under driving the receiver. When using 50/125
µ
m cable, install the long
range jumper (J607) even for very short cable lengths.
A 100/140
µ
m diameter cable can also be used for cable lengths less than 1500 feet. Use of this cable requires that
the range jumper J607 be set to normal. This setting will provide protection against overdriving the receiver.
Plastic cable is not recommended due to the coupling efficiency of the cable, which at short lengths will overload
the optical receiver. In addition, the large cable attenuation normally associated with plastic cable limits the useful
link lengths to a fraction of that achievable with glass cable.
7.1.1 Fiber Optic Cable Lengths
Calculate cable length by determining the output power of the transmitter (P
TX
) and the input receive level (Peak
Input Power Logic Level Low Receiver Sensitivity, P
RX
). The difference between the two numbers is the optical
power budget (P
B
’).
P
B
’ = P
TX
– P
RX
For example, if transmitter output power is -16 dBm and the input receive level is -24 dBm, the optical power
budget is then 8 dBm. Subtract from this value the fixed losses (i.e. connector losses, splice losses, P
Loss
) to obtain
the real power budget (P
B
).