Author: PLC Play Ground
Encoder Position Is Exactly Four Times Wrong? Check Quadrature Evaluation
An exact factor-of-two or factor-of-four position error often points to counting conventions.
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Absolute Encoder Values Jump Strangely? Check Gray Versus Binary
An SSI encoder can communicate reliably while its position is decoded incorrectly.
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IO-Link Sensor Is Fast—Why Does the PLC Update Slowly?
IO-Link communication speed is only one part of the update path.
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EtherNet/IP Device Pings but Rejects I/O? Check the Existing Owner
An EtherNet/IP device can answer network requests while rejecting a cyclic I/O connection because ownership is already assigned.
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PROFINET Device Is Online but a Module Is Red? Compare the Subslots
A reachable PROFINET device can still have an incompatible module or submodule configuration.
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OPC UA Certificate Is Trusted, but Login Still Fails? Check User Policy
Application trust and user authentication are separate parts of an OPC UA connection.
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MQTT Publisher Works, Subscriber Gets Nothing? Compare Every Character
A tiny topic-name difference can separate a working publisher from a silent subscriber.
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Elapsed Time Goes Negative After Clock Sync? Use the Right Clock
Wall-clock corrections can break duration calculations that subtract calendar timestamps.
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Every Device Slows Down at Once? Look for a Layer-2 Traffic Storm
A simultaneous slowdown across many devices can indicate excessive network traffic.
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IO-Link Device Is Online—But Is Its Measurement Valid?
An online IO-Link port does not guarantee that every process value is currently usable.
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