Question 1 QMED05 - Machinist-Pump Technician

The Correct Answer is A. **Why option A ("Compound gauge") is correct:** A compound gauge is a specialized type of Bourdon tube pressure gauge designed to measure pressure both above and below atmospheric pressure. It typically displays positive pressure (gauge pressure, often measured in psi or bar) and negative pressure (vacuum, often measured in inches of mercury ["Hg] or negative bar/psi) on the same dial. Therefore, it is capable of measuring and displaying both positive and negative pressures. **Why each of the other options is incorrect:** * **B) Differential pressure gauge:** A differential pressure gauge measures the *difference* between two separate pressure points (P1 - P2). While it can indicate a positive or negative difference, it is fundamentally designed to measure pressure drop or flow across a component, not the absolute positive and negative gauge pressure relative to the atmosphere, as a compound gauge does. * **C) Duplex gauge:** A duplex gauge (or dual gauge) contains two separate sensing elements and displays two distinct, unrelated pressures on a single housing or dial face. Both readings are typically positive pressures (e.g., measuring pump inlet and outlet pressure simultaneously). It does not inherently measure both positive and vacuum pressure on one scale. * **D) Simplex gauge:** A simplex gauge is a standard, single-reading pressure gauge. It is typically designed to measure either positive pressure (most common) or vacuum pressure, but not both on the same integrated scale like a compound gauge.