Siemens Simatic S7-200 System Manual page 450

S7-200 Troubleshooting Guide
Table H-1 S7-200 Troubleshooting Guide, continued
Problem Possible Causes
Power supply Over-voltage on the power lines
damaged. coming to the unit.
Electrical noise Improper grounding
problems
Routing on wiring within the
control cabinet.
Intermittent Excess vibration
values from values from
Improper mounting of the standard
expansion I/O
(DIN) rail
modules modules
The plastic connecting joints were not
completely removed when the bus
expansion cover was snapped out.
Defective bus connector
Communication The RS-485 port on the S7-200 CPU
network is and the PC/PPI cable are not isolated
damaged when (unless otherwise noted on the product
connecting to an data sheet).
external device.
The communication cable can provide
(Either the port a path for unwanted currents if all
on the non-isolated devices (such as PLCs,
computer, the computers or other devices) that are
port on the PLC, connected to the network do not share
or the PC/PPI the same circuit common reference.
cable is The unwanted currents can cause
damaged.) communication errors or damage to
the circuits.
STEP 7-Micro/WIN Communication problems
Error Handling
H-2
Solution
Connect a line analyzer to the system to check the
magnitude and duration of the over-voltage spikes.
Based on this information, add the proper type arrestor
device to your system.
Refer to the wiring guidelines in Section 2.3 for
information about installing the field wiring.
Refer to the wiring guidelines in Section 2.3. It is very
important that the control panel is connected to a good
ground and that high voltage wiring is not run in parallel
with low voltage wiring.
Connect the M terminal on the 24 VDC Sensor Power
Supply to ground.
Refer to Section A.1 for the sinusoidal vibration limits.
If the system is counted on a standard (DIN) rail, refer to
Section 2.2.
Refer to Section 2.2 for information about installing
expansion modules.
Replace the I/O bus connector.
Refer to the wiring guidelines in Section 2.3, and to
the network guidelines in Chapter 9.
Purchase an isolated RS485-to-RS232 adapter (not
supplied by Siemens) to use in place of the PC/PPI
cable.
Purchase an isolated RS485-to-RS485 repeater
when connecting machines that do not have a
common electrical reference.
Refer to Chapter 9 for information about network
comunications.
Refer to Appendix C for information about error codes.
S7-200 Programmable Controller System Manual
C79000-G7076-C230-02