Which of the following units is commonly used by a compound pressure gauge to measure the low side pressure in a system?

• A. Pa (pascals)
• B. psi (pounds per square inch)
• C. atm (atmospheres)
• D. mmHg (millimeters of mercury)

Answer: (B)

Verified step by step guidance

1. Understand that pressure gauges measure the force exerted by a fluid per unit area, and different units are used depending on the application and scale of pressure.
2. Recognize that the low side pressure in systems such as refrigeration or automotive air conditioning is typically measured in units that are practical for moderate pressures, not extremely small or large units.
3. Recall that pascals (Pa) are the SI unit for pressure but are often too small for practical use in many mechanical systems, making them less common for low side pressure gauges.
4. Consider that atmospheres (atm) are a large unit of pressure, more suitable for measuring atmospheric or very high pressures, so they are not commonly used for low side pressure gauges.
5. Identify that psi (pounds per square inch) is a common unit in the United States for measuring pressures in mechanical systems, including low side pressures, because it is convenient and widely understood; mmHg is also used but less common for low side gauges compared to psi.