Note
Read the tag map before you trust the dashboard
Dashboards compress. They also rename. A tile called “Line 2 speed” might be a calculated average, a last-good value, or a number the integrator typed during a demo and never replaced.
On a food line in Shah Alam the IoT application showed a CIP return temperature that always sat in spec. The RTD in the pipe did not. A Node-RED flow had a default of 72°C on timeout, and the probe cable had been loose for weeks. The control interlock in the same flow used the defaulted value, so the valve programme continued.
We now start most telemetry reviews with three artefacts: the vendor tag list, a short capture of what the broker actually carries, and a photograph of the sensor with its loop number. If those three disagree, we do not argue about the UI.
Operators are not at fault for believing the screen. The application is at fault for presenting a substitute as a measurement. When you ask us to audit a control app, budget an afternoon to walk the first dozen tags to the field. It is slower than a document review and it is the part that changes what we write in the report.