Field Instrument NotesProcess Instrumentation & Control
Notes from the field

Practical process instrumentation, explained the way it is used on site

Loop checks, transmitter calibration, P&ID reading and signal troubleshooting β€” written up as plain, reusable field notes with diagrams.

Start with 4–20 mA loops β†’
12.00 mA Β· 50 % DCS PT-101 trend
3in-depth notes
11original diagrams
5topics in progress
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Latest notes

Step-by-step write-ups with worked examples and diagrams.

How a basic control loop fits together

The path every measurement takes, from the process to the final control element.

SensorTE Β· FE Β· PE Transmitter4–20 mA / HART ControllerPID in DCS / PLC Final elementcontrol valve Β· VFD the process responds β€” and the sensor measures the change (feedback)

Measure β†’ transmit β†’ compare with setpoint β†’ act. Each note on this site covers one part of this chain.

Topics in progress

Notes currently being written up.

  • HART communication basics Coming soonDigital data on top of the analog signal, loop resistance and multidrop.
  • Differential pressure flow measurement Coming soonOrifice plates, square-root extraction and impulse line practice.
  • Control valve positioners Coming soonStroke checks, fail action and diagnosing sticky valves.
  • RTDs vs thermocouples Coming soonChoosing a sensor, wiring errors and cold-junction compensation.
  • Loop checks during commissioning Coming soonOrganizing a loop folder and signing off a loop.