Epson RC620 Manual page 189

♦ Causes of Error
Possible Cause
 Disconnected
terminating
resistors
 Cable
disconnection
 Disconnected
connector
 Disconnected
signal wire
 Loose connector
 Loose signal wire
 Electrical surges of
device power
supply
 Noise
(external cause)
 Broken unit
 No cause is
identified.
RC620 Option Fieldbus I/O Rev.8
Examination Method
(1) Check that terminating
resistors are connected to
both ends of the network.
(2) Measure resistance between
signal wires with device
power supply OFF.
→ Normal: 100 to 120 Ω
 Measuring point: Connection
of the trouble unit
 For details, refer to the section
4.2.3.1 Connection Problem.
Check for the connection of
connectors and signal wires.
→ The connectors and signal
wires should be firmly
connected.
 Checkpoint: all stations and all
branch taps
 For details, refer to the section
4.2.3.2 Loose Connector and
Signal Wire.
Measure voltage of the device
power supply at the trouble unit.
→ It should be within the range
of sufficient voltage for device
operation.
Check the noise intrusion via the
following paths (1) to (3).
(1) Noise via shield
(2) Induced noise via
communication cable
(3) Device power supply
→ For details, refer to the section
4.2.3.3 Noise Intrusion.
Replace the trouble unit with a
new one.
→ Verify whether the problem is
fixed.
Identify the trouble point by
dividing the network.
→ For details, refer to the section
4.2.3.4 Broken Unit
Examination.
4. Troubleshooting (PROFIBUS DP)
Countermeasure
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 220
Ω.
Connect the connectors and
signal wires again.
Check voltage of the device
power supply.
Take countermeasures
against noise.
Replace the unit with a new
one.
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