Question 48

The Correct Answer is D **Why option D ("Duplex gauge") is correct:** A **Duplex gauge** (or duplex pressure gauge) is specifically designed to measure and display two independent pressures simultaneously using a single housing and dial face. It typically achieves this by incorporating two separate internal sensing mechanisms (like two Bourdon tubes) and two corresponding pointers, allowing the operator to read two distinct pressure sources at the same time. This capability directly satisfies the requirement of measuring and displaying two pressures simultaneously. **Why each of the other options is incorrect:** * **A) Differential pressure gauge:** A differential pressure gauge measures the *difference* between two pressures ($\text{P}_1 - \text{P}_2$) and displays this single value. It does not display the two input pressures ($\text{P}_1$ and $\text{P}_2$) independently and simultaneously. * **B) Compound gauge:** A compound gauge is a single-reading gauge capable of measuring both positive pressure (above atmospheric) and vacuum (below atmospheric) on a single scale. It measures only one pressure source at a time. * **C) Simplex gauge:** A simplex gauge is the standard term for a single-reading pressure gauge. It measures and displays the pressure from only one source.