Author: PLC Play Ground
SCADA Connects by IP but Fails by Name? Follow DNS Resolution
A successful IP connection with a failed hostname connection points toward name resolution or name-dependent service configuration.
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RS-485 Fails When One More Device Is Added? Check the Electrical Bus
Adding one RS-485 device changes more than the address list.
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Temperature Changes When the Cabinet Warms? Check Cold-Junction Compensation
A thermocouple reading depends on more than the probe temperature.
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New 5/3 Valve Changes Cylinder Behavior at Rest? Check the Center Symbol
Five ports and three positions do not fully identify a valve function.
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HMI Displays Fahrenheit but Writes Celsius? Test Both Directions
A converted display can look correct while an operator entry writes the wrong units.
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Database Is Back but History Is Still Missing? Inspect Store-and-Forward
Restoring a database connection does not guarantee that queued history has been written successfully.
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Production Report Repeats an Hour? Check Daylight-Saving Time
Local clock labels can repeat during a daylight-saving transition.
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Two Trends Look Identical but Values Differ? Check the Axes
Chart shape alone does not establish equal values or a causal relationship.
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OEE Jumps After a Dashboard Update? Audit the Denominator
An OEE improvement can come from a changed calculation rather than changed production.
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The Spare PLC Is the Right Model but Still Unsuitable? Check Compatibility
Matching the catalog number is only part of a replacement plan.
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