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Network Configuration Section 2-2
Checking the Installation
of Terminating Resistors If communications errors occur when setting up the system, it is possible to
check whether or not the Terminating Resistors are connected properly. Turn
OFF the network power supply and use a multimeter to test the resistance
between any node’s CAN H signal wire (white) and CAN L signal wire (blue).
• A normal resistance reading is 50 to 70
Ω
.
• If the resistance is greater than 70
Ω
, there may be a broken signal line
in the network or one or both Terminating Resistors may be missing.
A reading of about 100
Ω
indicates that one Terminating Resistor is
missing.
A reading of about 300
Ω
or higher indicates that both Terminating Re-
sistors are missing.
• If the resistance is less than 50
Ω
, there may be too many Terminating
Resistors (3 or more) in the network.
Note Do not test the resistance while the network is operating. Errors will occur in
the communications data and could cause unexpected problems.
2-2-8 Using Crimp Terminals
We strongly recommend the use of crimp terminals (solderless pin terminals)
on the wires that connect to the communications cable connectors. The fol-
lowing problems may occur if crimp terminals are not used.
1. A stray wire strand may contact the adjacent terminal and cause a short.
2. The cable may pull out of the connector.
3. The contact between the wire and connector may be poor.
Refer to 2-4 Wiring Methods for information on recommended crimp termi-
nals.
2-2-9 Sharing the Communications and Internal Circuit Power Supply
To avoid noise problems, it is generally recommended to provide separate
communications and internal circuit power supplies, but the same power sup-
ply can be used for both purposes if necessary.
When a power supply is shared for the communications and internal circuit
power supplies, wire the network as shown in configuration A. Do not use con-
figuration B because it will generate more noise than configuration A.
Ω
Multimeter
Use a multimeter to
measure the resistance
between the signal wires.
Blue (CAN L) White (CAN H)