Find and rectify cable connection error

1. Selan network

Symptom

Diagnosis

Reason

Measures

Machine cannot be accessed via Selan

Signal path incorrect (remeasure with oscilloscope)

Long lines

Too many machines in the network:
- subdivide into a number of branches
- fewer machines per branch
In most cases, the machine's I/O card does not need to be changed.

Malfunction in Selan connection

Crosstalk in switching operation on the Selan cable

Electromagnetic disturbance from the network cables, transformers or electrical motors

Move Selan cable away from the network cable (e.g. feed line to neon tubes or gas discharge lamps)

Transfer rate poor

Long lines

Too many machines in individual network branches. Subdivide into a number of branches with fewer machines per branch.

2. Ethernet in general

Symptom

Diagnosis

Reason

Measures

Network output too low

Induced interference voltage

Electromagnetic interference fields in the vicinity of a cable or signal irradiation originating in a faulty connector that acts as an antenna.

Check cable installation. Be sure to keep the latter away from electric supply lines, electric motors and transformers

Loose or faulty connections

Check plug-in connections

Increased number of collisions (> 60%)

Excessively long cable, too many consecutive hubs (max. nesting depth 4), faulty transceiver, missing or faulty terminal resistance, different cable impedances

Check network configuration and reconfigure if necessary; reduce number of emergency segments by half and localize damaged spot by analyzing partial segments; use standardized cable only

3. Ethernet via twisted pair cable

Symptom

Diagnosis

Reason

Measures

Total failure of a segment

Short circuit;
Activity LED at hub fails to light up
Interference measurement reveals low resistance

Mechanical damage: cable crushed or cracked

Localize damaged spot and replace cable

no connection
Activity LED at hub fails to light up
Resistance measurement reading shows infinite value

Mechanical damage; loose connector

Localize damaged spot and replace cable

Anomalous collisions and data fragments

Induced interference voltage

Electromagnetic interference fields in the vicinity of the cable
Unshielded cables are prone to this

Check cable installation. Keep cables away from electric supply lines, electric motors and transformers

Sporadic network failure

High attenuation;
activity LED at hub fails to light up

Cable with high loss rate, different impedances, lines that are unsuitable for high-frequency signals

Use localizing and standardized Category 7 lines