Module 1 - Measurement

Module from the Instrumentation Engineering Curriculum curriculum.

MEASUREMENT PRINCIPLES · Learning Objectives · 1. Select appropriate pressure measurement technology for process conditions 2. Choose between RTD and thermocouple for temperature measurement 3. Compare flow measurement technologies and their applications 4. Understand level measurement principles and limitations 5. Apply analytical measurement for critical process variables · Temperature Measurement Technologies

Technology	Sensor Type	Range	Accuracy	Application	Limitations	Cost
RTD (Pt100)	Platinum resistance, 100Ω at 32°F	−328 to +1112°F	±0.2-0.5°F	Process temperature, custody transfer, lab	Slow response, self-heating, requires 3/4-wire	$200-500
Thermocouple Type J	Iron / Constantan	32 to +1382°F	±2-4°F	General process, furnaces (oxidizing)	Not for reducing atmosphere, iron corrodes above 1000°F	$20-80
Thermocouple Type K	Chromel / Alumel	−328 to +2282°F	±2-4°F	Most common — general purpose, furnaces, kilns	Drift above 1800°F, green rot in reducing +1600°F	$20-80
Thermocouple Type N	Nicrosil / Nisil	−328 to +2282°F	±2-4°F	Better stability than K above 1000°F	Not widely stocked, fewer reference tables	$30-100
Thermocouple Type R/S	Pt-Rh / Pt	32 to +2642°F	±1.5-3°F	High-temperature furnaces, glass, ceramics	Expensive, contamination sensitive, needs pure atmosphere	$300-1000
IR Pyrometer	Non-contact infrared	−58 to +5432°F	±1-2% of reading	Rotating equipment, moving objects, refractory surfaces	Emissivity uncertainty, dirty optics, atmospheric absorption	$500-3000
Bimetallic	Coiled bimetallic strip	−40 to +1000°F	±1-2% of span	Local indication, thermostats	No transmitter output, slow response, limited accuracy	$50-150
Flow Measurement Technologies
Technology	Principle	Accuracy	Best Application	Limitations	Rangeability	Pressure Drop
Orifice Plate	Differential pressure across restriction	±0.5-2%	Clean liquids and gases, steam — most common	Square-root relationship (poor at low flows), wear, clogging	3:1 to 5:1	Medium-High
Vortex	Frequency of vortices shed from bluff body	±0.5-1%	Steam, clean liquids and gases	Minimum Reynolds number required, vibration sensitive	10:1 to 20:1	Low-Medium
Coriolis	Mass flow via tube vibration frequency/phase shift	±0.1-0.2%	Custody transfer, batching, density measurement, slurries	Expensive, large/heavy, pressure drop at high flow	100:1	Medium
Magnetic	Faraday law — voltage from conductor (liquid) in magnetic field	±0.2-0.5%	Conductive liquids (water, acids, slurries), no pressure drop	Requires conductive fluid (>5 μS/cm), not for gases/hydrocarbons	100:1	Zero
Ultrasonic (transit time)	Time difference of upstream/downstream ultrasonic pulses	±0.5-1%	Large pipes, clean liquids, clamp-on (non-intrusive)	Requires clean fluid, no bubbles/solids	100:1	Zero
Turbine	Rotor speed proportional to velocity	±0.15-0.5%	Clean, low-viscosity liquids, custody transfer	Bearing wear, requires clean fluid, viscosity sensitive	10:1	Low
Thermal Mass	Heat transfer proportional to mass flow	±1-2%	Gas flow measurement, low-flow applications	Composition sensitive, requires calibration for specific gas	50:1	Very Low
Source: FOS Chief Files — Instrumentation Basics.ppt, Instrument Design Seminar, IPE-EP-12 series (transmitters, flow measurement)

Source: Instrumentation_Engineering_Curriculum_v1.xlsx · Sheet: Module 1 - Measurement

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