Walt — Simple Man Takeaway
Temperature tells a story. First prove whether the storyteller is honest.
Plain-English Summary
Use this flow when temperature readings drift, jump, fail, lag, disagree with process reality, or cause quality, safety, or equipment issues. Temperature is often both a process variable and a symptom. The sensor may be wrong, or the machine may really be changing temperature because heat is not entering or leaving correctly.
R.E.A.L. firstProve process truthCapture before changingCompare field state to logic stateHumans remain authoritative
Sensor / Instrument First-Check Flow
Field Checks
- Sensor type and matching input configuration
- HMI reading vs. PLC raw value vs. field transmitter vs. local gauge
- Units, scaling, compensation, sensor type
- Wiring, terminals, shield, extension wire, polarity
- Sensor placement, thermal contact, well condition, response time
- Heating/cooling flow path and real process temperature
- Heaters, SSRs, contactors, valves, chillers, pumps, heat exchangers
- Calibration history and replacement sensor match
- Startup vs. steady-state behavior
Watch Out For
- Blaming the sensor when heat transfer is actually failing
- Wrong RTD/thermocouple type in input configuration
- Sensor installed poorly so it sees the wrong temperature
- Filtering hiding short events
- Cooling/heating utilities causing temperature drift
- Temperature safety limits bypassed casually
Reverse-Trace / Ghost Busting™ Decision
if temperature permissive, heater enable, cooling valve command, pump command, or alarm logic is blocked.
if the temperature value spikes, dips, drops out, or crosses a limit briefly and recovers before anyone sees it.
Recipe / Health Log
Record the good, the bad, and the in-between: real-world condition, sensor state, PLC input state, HMI display, logic use, product/material, method, atmosphere, utility condition, timing, symptom, corrective action, and result.
Related Calculators / S.W.A.T. Screens
Related Handbook / Flows
Walt says STOP! - Safety First
Make these checks prior to proceeding.
Stop and follow site procedures when heat, steam, hot water, oil, heaters, ovens, molds, chillers, chemicals, stored thermal energy, live electrical troubleshooting, or lockout/tagout requirements are involved. Do not bypass temperature safety limits without proper authority and procedure.