To measure inlet restriction, which instrument is used?

• A. Dial indicator
• B. Manometer
• C. Pyrometer
• D. Vernier caliper

Answer: (B)

Inlet restriction is assessed by measuring the pressure difference (vacuum) in the intake as air flows through the system. A manometer is designed to read this kind of pressure difference, translating the vacuum into a clear liquid-column height (often inches of water or mmHg). By placing the manometer between the intake plenum and atmospheric reference, you can directly see how much restriction is present—the greater the vacuum, the greater the restriction.

The other tools aren’t suited for this purpose: a dial indicator measures small linear movement, not pressure; a pyrometer measures temperature; and a Vernier caliper measures dimensions.