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Instrumentation, explained

Practical notes for instrument and control engineers. A structured series, from the basics of a measurement loop to transmitters, sensors, signals, control systems, final elements and safety. Each article covers one topic, works through an example with numbers and ends with a checklist you can use on your next datasheet.

Module 1 Instrumentation basics

  1. 1.1What instrumentation does in a process plant: measure, control, protect
  2. 1.2The instrument loop: sensor, transmitter, controller, final element
  3. 1.3Reading P&ID symbols and ISA 5.1 tag numbers
  4. 1.4Range, span, accuracy, repeatability and turndown
  5. 1.5Gauge, absolute and differential pressure, and units
  6. 1.6The instrument deliverables: index, datasheet, hook-up, loop diagram, I/O list

Module 2 Pressure

  1. 2.1Pressure sensors: strain gauge, capacitive, piezoresistive, resonant
  2. 2.2Pressure transmitters: ranging, damping, over-range
  3. 2.3DP transmitters and manifolds (3-valve, 5-valve)
  4. 2.4Diaphragm seals and capillary temperature errors
  5. 2.5Pressure gauges per EN 837: class, case, siphons, snubbers
  6. 2.6Impulse lines: slopes, sealing, gas versus liquid service

Module 3 Temperature

  1. 3.1RTDs: Pt100 classes and 2-, 3- and 4-wire errors
  2. 3.2Thermocouples: types, tolerances, cold junction, extension cable
  3. 3.3RTD or thermocouple: how to choose
  4. 3.4Temperature transmitters: head or rail mounted, sensor matching
  5. 3.5Thermowells: types, immersion, response time
  6. 3.6Thermowell wake frequency (ASME PTC 19.3 TW)

Module 4 Flow

  1. 4.1Flow basics: velocity profile, Reynolds number, straight runs
  2. 4.2Orifice plates: β ratio, differential choice, ISO 5167 sizing
  3. 4.3Venturis, nozzles and pitot tubes
  4. 4.4Magnetic flowmeters: conductivity, liners, grounding
  5. 4.5Coriolis meters: sizing, pressure drop, density
  6. 4.6Vortex, turbine and positive displacement meters
  7. 4.7Ultrasonic meters: in-line and clamp-on
  8. 4.8Choosing a flowmeter: a decision table

Module 5 Level

  1. 5.1DP level: wet and dry legs, density effects
  2. 5.2Radar level: free-space, guided wave, stilling wells
  3. 5.3Displacers, floats and magnetic level gauges
  4. 5.4Ultrasonic, capacitance and nuclear level
  5. 5.5Interface level measurement
  6. 5.6Level switches: vibrating fork and float

Module 6 Analysers and gas detection

  1. 6.1Analyser basics: sample systems, lag time, T90
  2. 6.2O2, pH, conductivity and moisture analysers
  3. 6.3Gas chromatographs: an overview
  4. 6.4Gas detection: catalytic, IR, electrochemical, and placement

Module 7 Signals and communication

  1. 7.14–20 mA: loop power, burden and loop resistance calculation
  2. 7.2NAMUR NE43 failure currents in depth
  3. 7.3HART: what it adds, multidrop
  4. 7.4Discrete signals: dry contacts, NAMUR proximity, wetted contacts
  5. 7.5Fieldbus basics: Foundation Fieldbus, PROFIBUS PA, Modbus
  6. 7.6Wiring and cabling: shielding, earthing, segregation

Module 8 Control systems

  1. 8.1DCS, PLC and SIS: what each does
  2. 8.2I/O types and the I/O list: AI, AO, DI, DO
  3. 8.3Marshalling, junction boxes and cable schedules
  4. 8.4Loop diagrams: how to read and make one
  5. 8.5Control system configuration basics: tags, ranges, scaling, alarms
  6. 8.6Alarm management: priorities and set points (EEMUA 191 / ISA 18.2)

Module 9 Control

  1. 9.1PID control in plain words
  2. 9.2Control loop tuning basics
  3. 9.3Cascade, ratio and feedforward control
  4. 9.4Split range and override control

Module 10 Final elements

  1. 10.1Control valve basics: bodies, trims, characteristics
  2. 10.2Control valve sizing (IEC 60534-2-1), worked example
  3. 10.3Choked flow, cavitation and flashing
  4. 10.4Control valve noise (IEC 60534-8-3)
  5. 10.5Actuators, fail positions and actuator sizing
  6. 10.6Positioners, solenoids and limit switches
  7. 10.7On/off valves and motor-operated valves

Module 11 Safety and hazardous areas

  1. 11.1Hazardous areas: zones, gas groups, T-classes
  2. 11.2Ex protection methods and reading Ex marking
  3. 11.3Intrinsic safety loop calculation
  4. 11.4Pressure relief valves: API 520 sizing, 3 % inlet loss, 10 % back pressure
  5. 11.5SIL basics: IEC 61511, SIF, proof testing
  6. 11.6NACE MR0175 / ISO 15156 and sour service on a datasheet

Module 12 Projects and commissioning

  1. 12.1Instrument datasheets: the fields people get wrong
  2. 12.2Calibration and loop checks
  3. 12.3Commissioning, FAT and SAT for instruments