Author: PLC Play Ground
RTD Reads Warmer Than the Process? Check Excitation Self-Heating
An RTD measurement requires excitation current, which also generates heat in the sensor.
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Thermocouple Suddenly Reads Extreme Heat? Check Open-Sensor Status
An extreme temperature can be an open-sensor response rather than real process heat.
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4–20 mA Works Near Zero but Fails Near Full Scale? Check Loop Voltage
A current loop needs enough voltage to drive its highest intended current through every series load.
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A 250-Ohm Resistor Changed Your Signal? Check Burden and Scaling
A resistor used to convert loop current into voltage affects both scaling and the loop burden.
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More ADC Bits but the Same Measurement Error? Separate Resolution From Accuracy
More displayed digits or converter bits do not guarantee a more accurate measurement.
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Analog Value Flatlines at the Top? Find the Saturating Stage
A flat upper reading can mean the measurement chain has reached a limit.
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Pressure Reading Is Suspiciously Smooth? Check the Impulse Line
A stable pressure trend is not always evidence of a stable process.
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Tank Level Changes After a Product Swap? Check Density Assumptions
Hydrostatic level measurement depends on liquid density.
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Magnetic Flowmeter Looks Alive in a Partly Empty Pipe? Check Measurement Validity
A powered electromagnetic flowmeter does not guarantee a valid flow measurement.
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Two Gas Flowmeters Disagree? Check Actual Versus Standard Volume
Gas volume flow is incomplete without pressure and temperature reference conditions.
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