Where the equipment lives.
Bolted to a steel pole in the desert, buried beside a pipeline, or inside a plant with no air conditioning. These are the environments we spec our products against. Nicer conditions are welcome.
Energy
Long distances, no shelter, classified areas, and a fault that has to be found before somebody drives four hours to it. Complex branched piping where flow balance struggles and where a controlled leak can actually be created for calibration.
Utilities
Electrically hostile, timing-critical, and unforgiving of a device that reboots. Substations need microsecond time for sampled values and line differential protection, and today they take it from a single satellite source that cannot check itself.
Manufacturing
Inspection at line speed. The defects that matter are smaller than the eye can catch, and the answer has to arrive before the next part does.
Ports and airports
Position and time are operational here, not administrative. Fuel hydrant networks are short, the sensors are reachable and the power is already there. That makes them one of the few places a leak detector can be checked against reality instead of against a model.
Talk to engineering.
Start from a specification, a drawing, an isometric or a photograph of what you are trying to instrument. The first questions are the same every time: what is in it, at what pressure, what it is made of, how long the run is, and what runs beside it that makes noise.