Instrumentation
Industrial Sensors
Proximity, temperature, pressure, and flow measurement behavior.
Overview
Industrial sensors translate physical reality into signals; each technology — inductive, capacitive, RTD, thermocouple, pressure, flow — has characteristic blind spots and drift behavior.
Engineering purpose
Provide the measurements every control decision rests on, with accuracy and reliability matched to the process duty.
How it works
Proximity sensors detect via field disturbance within a rated sensing distance; RTDs vary resistance nearly linearly with temperature; thermocouples generate junction EMF needing cold-junction compensation; pressure and flow devices depend on correct process connections.
- Inductive proximity sensors detect metals only; capacitive types detect non-metals but drift with humidity.
- RTDs (PT100) suit precision below ~600 °C; thermocouples suit high temperature and fast response.
- Pressure and flow readings depend on correct process connections — trapped air or sediment biases them.
Common faults
Capacitive sensors drifting with humidity; misalignment after mechanical work; impulse-line plugging mimicking sensor failure; wrong-type extension cable corrupting thermocouple readings.
Diagnostic checks
- 1Compare the sensor reading against a local gauge or portable reference.
- 2Inspect sensing distance and target alignment after any mechanical work.
- 3Compare the suspect reading against an independent local reference before condemning the instrument.
Safety notes
Measurements feeding protective decisions need defined failure behavior — know whether each sensor fails high, low, or frozen, and design the response.
Commissioning notes
Verify sensing distance and alignment in final mechanical position; document each instrument's range, tag, and as-found calibration.
Related concepts
Sensing technologies, cold-junction compensation, impulse lines, calibration references, failure modes.
sensor · proximity · pt100 · rtd · thermocouple · flow · سنسور · پراکسیمیتی · ترموکوپل · دبی
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