🔍 Key Concepts

• Direct reading pressure gauges and how many pressure inputs each type can accept • The meaning of simplex, duplex, compound, and differential in instrumentation terminology • How a gauge that compares two pressures differs from a gauge that simply shows two separate pressures

💭 Think About

• For each gauge type in the choices, ask yourself: does it have one sensing element or two separate sensing elements? • Which type is primarily designed to show the difference between two pressures, and which is designed to show two independent pressures side by side? • Think about common applications: boiler systems, hydraulic systems, and fuel systems — where might you need to watch two separate lines at once?

✅ Before You Answer

• Verify which option specifically means two independent bourdon tubes / sensing elements with two pointers in one case • Confirm that a compound gauge still has only one connection point even though it shows both vacuum and pressure ranges • Confirm that a differential pressure gauge usually has two pressure connections but one indication showing the difference, not two separate readings