Instrumentation and control

Practical Procedure · Calibration Gas Analyzer Calibration — Zero and Span, Zirconia / NDIR Applies to: Zirconia oxygen analyzers, NDIR (CO/CO2/SO2 etc.) analyzers  |  Equipment needed: Zero gas cylinder, span gas cylinder (certified concentration), flow regulator Zero and Span — See the Flow Tap a tab to switch the diagram, then tap "Show Correction" to see the reading before and after calibration. Zero Gas Step Span Gas Step Zero Gas Cylinder Cert. 0.0% Analyzer Zero adjust 1.8% 0.0% reading vs 0.0% Output Signal to PLC/DCS 4–20 mA / digital Span Gas Cylinder Cert. 20.9% Analyzer Span adjust 19.4% 20.9% reading vs 20.9% Ou...

Practical Procedure · Calibration HART Transmitter Trim — Digital Trim vs. Analog (Loop) Trim Applies to: Smart HART transmitters  |  Equipment needed: HART communicator, pressure/process reference standard, mA reference meter Two Different Trims — See the Difference Tap a tab to switch the diagram, then tap "Show Correction" to see the value before and after trim. Digital (Sensor) Trim Analog (Loop) Trim Reference Applied Pressure 50.0 units Transmitter Internal Sensor 52.6 mA-eq 50.0 mA-eq reading vs reference HART Comm 4–20 mA Output unchanged by digital trim Transmitter Sensor OK Output stage HART Comm Loop Output ...

Practical Procedure · Calibration Control Valve Positioner Calibration — Full Stroke, Limits, and Auto vs. Manual Applies to: Pneumatic control valves with smart/digital positioners (e.g. HART-based) or conventional analog positioners  |  Equipment needed: HART communicator (for smart positioners), air supply/regulator, mA source or 4–20 mA loop calibrator Control Valve: Throttling the Flow ACTUATOR As the PLC output signal changes, the actuator rotates the internal disc — from fully open (parallel to flow) toward fully closed (perpendicular to flow). This is exactly why a control valve isn't just "on/off" like a block valve: it throttles anywhere between 0% and 100% to hold a process variable at setpoint. Before You Start Confirm the valve is safe to stroke — coordinate with operations, since a full 0–100% stroke will move the valve through its complete range on a live process line. Chec...

Instrumentation Basics: How a Process Actually "Talks" to a Control System If you're new to a cement plant, power station, or any process industry, the first thing that confuses everyone is this: how does a control room operator, sitting far away from the kiln or the mill, know what's happening inside a pipe, a vessel, or a rotating drum? The answer is instrumentation. In this post I'll break down the basics the way I explain it to new technicians on my own panel — no textbook language, just what you actually need to know on the floor. 1. Every Instrument Does One of Three Jobs No matter how complicated the nameplate looks, every field instrument is doing one of three things: Sensing — measuring something physical (temperature, pressure, level, flow, speed) Transmitting — converting that measurement into a signal the control system can read Actuating — taking a command from the control system and physically doing something (opening a valve, startin...

Practical Procedure · Calibration Load Cell Calibration for Weigh Feeders — Dead-Load, Test-Weight, and Why Shunt Calibration Isn't Enough Applies to: Belt weigh feeders, weigh hoppers with load cell-based measurement  |  Equipment needed: Certified test weights or a dead-load/material reference, shunt calibration resistor (if supported), digital indicator/weigh controller access Before You Start Confirm the feeder/hopper is mechanically free — check idlers, belt tension, and load cell mounting for anything that could add friction or false load before assuming a load cell problem. Check load cell cabling and junction box connections for corrosion or loose terminations, especially in dusty or humid plant environments. Note whether the system uses a single load cell or multiple load cells summed together — multi-cell systems need each cell checked individually, not just the combined output. Method 1 — Shunt Calibration Shunt calibration simulates a known load...

Practical Procedure · Calibration RTD Calibration and Verification — Dry-Block vs. Ice-Point Method Applies to: RTD temperature sensors (Pt100/Pt1000, 2/3/4-wire)  |  Equipment needed: Dry-block calibrator or ice bath, precision reference thermometer, multimeter/ohmmeter Pt100 RTD: Resistance Rises With Temperature Resistance (Ω) 194Ω 138Ω 100Ω 0°C 100°C 250°C Temperature (°C) A Pt100 RTD starts at 100Ω at 0°C and increases by roughly 0.385Ω per °C — nearly linear across its working range. That predictable, repeatable relationship is exactly why RTDs are trusted for precision temperature measurement over thermocouples in the range where both could work. Before You Start Note the RTD type (Pt100 or Pt1000) and wiring configuration (2-wire, 3-wire, or 4-wire) — this affects both how you measure and how much lead resistance error matters. Isolate the...