🔍 Key Concepts

• Bourdon tube pressure gauge mechanism – how movement of the tube is transferred to the pointer • Difference between zero set (calibration at zero) and changing the entire scale or sensitivity • Which parts of the gauge change indication only, versus those that would change the tube’s physical/elastic characteristics

💭 Think About

• Ask yourself: If the gauge reads pressure when it is actually vented to atmosphere, what small adjustment would you make so that the pointer reads exactly zero without affecting the tube’s elastic behavior? • Which option changes just the indication at zero, and which options would change the relationship between pressure and pointer travel across the whole range? • Think about which adjustment is normally designed to be repeatable and precise for calibration, versus something that would be considered damage or a crude fix.

✅ Before You Answer

• Identify which choice alters the mechanical linkage ratio between tube movement and pointer movement (this affects span, not just zero). • Identify which choices would likely permanently deform the sensing element or pointer (more like damage than a proper calibration step). • Focus on the option that lets you line up the pointer at zero when no pressure is applied, while leaving the pressure–deflection characteristic of the tube unchanged.