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E6581402c
-10-
3.3. Network cable connection
Connect t he BACnet network cable to communication option as follows.
Title Description
Wire type Shielded tw isted cable
Characteristic impedance Between 100 and 130 ohm
Distributed impedance between
conductors
Less than 100pF per meter
Distributed impedance between
conductors and shield
Less than 200pF per meter
Foil or braided shields are acceptable.
Length of an MSTP segment 1200 meters with AWG18 (0.8mm
2
)
Cable sheath should be peeled off by a bout 7mm.
For wiring work, use a flat blade screwdriver with a 0.6mm thick and
3.5mm width blade.
Tightening torque for the terminal block is 0.5Nm.
* Fix a cable so that a communication connector may be not taken the weight of wire.
3.4. Network configuration
Make up the net work as follows.
- Transmission/reception signals (A, B)
Make up the communication path by connecting all transmission/reception data cables.
- Signal common (GND)
GND is t he signal common.
- Grounding the shield of cable (SCR)
Connect the all shield lines of network cable. The shield shall be grounded at one end only prevent
currents from being created.
- Termination resistor
A termination resistance of 120 ohms plus or minus 5% shall be connected at each of the two ends
of the segment medium. This option has a termination resistor, so if use, set up the termination
resistor SW. (Refer to 2.1 Outline)
At least one set, and no more than two sets, of network bias resistors shall exist for each segment.
This option has local bias resistors.
Termination
B
A
GND
+5
510
510
Node with network
bias resistors
120
B
A
GND
Node without
bias resistors
B
A
GND
+5
47k
Node with local bias resistors
This option board
47k
4.7k
4.7k
Termination
120
SCR
Communication
cable
Communication
cable
SCRSCR
SW4
TERM
N.B.:Do not c onnect the SCR terminal to the power ground of inverters or other units.
Keep t he network cables 20cm or more separate from the power cables to prevent from
malfunctioning due to electromagnetic noise.
⿆
mm