4. Troubleshooting (DeviceNet)
♦
Causes of Error
Possible Cause
Examination Method
Countermeasure
{
Disconnected
terminating resistors
{
Cable disconnection
{
Disconnected
connector
{
Disconnected signal
wire
(1) Check that terminating
resistors are connected to
both ends of the network.
(2) Measure resistance
between signal wires with
communications power
supply OFF.
→
Normal: 50 to 70
Ω
z
Measuring point: Connection
of the trouble unit
z
For detail, refer to the section
4.1.3.1 Connection Problem
.
Fix the problem.
How to find the trouble
point:
Remove the terminating
resistor on one end of the
network. The trouble point
is where resistance changes
from 120
Ω
.
{
Loose connector
{
Loose signal wire
Check for the connection of
connectors and signal wires.
→
The connectors and signal
wires should be firmly
connected.
z
Checkpoint: all nodes and all
branch taps
z
For details, refer to the
section
4.1.3.2 Loose
Connector and Signal Wire
.
Connect the connectors and
signal wires again.
{
Voltage drop of
communications
power supply
Measure voltage of
communications power supply
at the unit with a trouble.
→
Normal: 11V or more
between V+ and V-
z
If the voltage is 11 to 14 V,
the unit is a possible cause.
Fix the problem on the unit.
Check the voltage of the
power supply.
Calculate the current
capacity of the cable and add
more communications power
supplies.
{
Noise
(external cause)
Check the noise intrusion via
the following paths (1) to (3).
(1) Noise via DRAIN (FG)
(2) Induced noise via
communication cable
(3) Communications power
supply
→
For details, refer to the
section
4.1.3.3 Noise
Intrusion
.
Take countermeasures
against noise.
{
Broken unit
Replace the broken unit with a
new one.
→
Verify whether the problem
is fixed.
Replace the unit with a new
one.
z
No cause is
identified.
Identify the trouble point by
dividing the network.
→
For details, refer to the
section
4.1.3.4 Broken Unit
Examination
.
Fieldbus I/O Rev.6
85
Содержание EM07ZS1647F
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