🔍 Key Concepts

• Differences between elastic mechanical gauges (like Bourdon tubes and compound gauges) and liquid column devices • Which instruments are best suited for very small, low positive pressures close to atmospheric pressure • How sensitivity and accuracy change with the type of pressure-measuring device

💭 Think About

• Which of these instruments can show a very small change in pressure as a relatively large, easily measured change in the instrument reading? • Think about which instrument is commonly used in laboratories or calibration setups when extremely small pressures or pressure differences must be measured. • Which devices here are typically used on shipboard machinery for medium/high pressures, and which are used for precise low-pressure measurement?

✅ Before You Answer

• Identify which option uses a column of liquid whose height changes with pressure. • Eliminate instruments that are primarily designed for high or combined positive/negative pressures, not for very low pressures. • Ask yourself: Which instrument is known for high sensitivity and accuracy in measuring small pressure differences?