Choosing a flowmeter: For fluids whose flow measurement should be largely insensitive to changes in density, viscosity, and velocity profile, the most suitable instrument is a:

Introduction / Context:
In process plants, flowmeters may suffer accuracy loss if fluid properties such as density and viscosity change. Selecting a technology that inherently decouples measurement from these properties saves recalibration effort and improves robustness.

Given Data / Assumptions:

• Fluid is electrically conductive (requirement for magnetic flowmeters).
• Measurement range covers laminar to turbulent regimes.
• Objective: insensitive to density, viscosity, and velocity profile distortions.

Concept / Approach:
By Faraday’s law, a magnetic flowmeter induces a voltage proportional to volumetric flow rate (E ∝ B * L * v). Since volumetric flow does not require calibration against density or viscosity, and since the meter has no obstruction (full-bore design), profile effects are minimized with appropriate straight runs. Therefore, mag meters excel when property independence is desired.

Step-by-Step Solution:

Verification / Alternative check:
Factory calibrations commonly remain valid over wide property variations for mag meters; many water/wastewater and slurry services rely on this advantage.

Why Other Options Are Wrong:

• Pitot/Flow nozzle: Differential pressure scales with density and is viscosity/Re-dependent.
• Turbine: K-factor shifts with viscosity/Re and profile; moving parts add sensitivity.
• Rotameter: Float position depends on density/viscosity; profile variations matter.

Common Pitfalls:
Forgetting conductivity requirement; non-conductive fluids (e.g., hydrocarbons) are unsuitable for mag meters.

Final Answer:
Magnetic flowmeter