Notches for flow measurement – common construction material In practice, is it correct that a thin-plate measuring notch (for example, a V-notch) is usually fabricated from metal?

Introduction / Context:
Notches (thin-plate weirs) are widely used for measuring small to moderate discharges. Material choice affects edge sharpness, durability, and calibration stability.

Given Data / Assumptions:

• Thin-plate construction is desired to obtain a sharp, well-defined crest.
• Edges must remain straight and burr-free over time.
• Field and laboratory applications are both considered.

Concept / Approach:
Metals such as stainless steel or brass provide dimensional stability, corrosion resistance, and the ability to machine a sharp crest that maintains calibration. While temporary or low-accuracy installations may use wood or plastics, standard practice for accurate measurement is a metallic thin plate.

Step-by-Step Solution:
Step 1: Identify requirements: sharp edge, minimal wear, smooth surface.Step 2: Compare materials: metals outperform wood in edge retention and moisture resistance.Step 3: Conclude that a metallic plate is usually chosen for notches intended for measurement.

Verification / Alternative check:
Calibration guidelines from labs and standards organizations typically specify thin, smooth metal plates for V-notch and rectangular notches to ensure reproducible coefficients.

Why Other Options Are Wrong:

• “Incorrect” or wood-as-standard: wood swells and blunts, degrading accuracy.
• Only for high heads or only for labs: metals are common across head ranges and in field installations.

Common Pitfalls:
Allowing burrs or corrosion at the crest; even with metal, maintenance is essential for accuracy.

Final Answer:
Correct