🔍 Key Concepts

• compound gage measures both pressure above atmospheric (pressure) and below atmospheric (vacuum) on the same dial • where in a system you might need to read both suction (vacuum) and positive pressure • typical locations of pressure gages on pumps, compressors, and engines

💭 Think About

• Ask yourself: in which of these four locations would it be important to know if the line is under vacuum as well as when it is under positive pressure? • Consider which systems normally operate only at positive pressure and which may experience both suction and discharge conditions. • Think about where the fluid is being drawn in versus pushed out: which side of a pump or machine would show vacuum if something is restricting the flow?

✅ Before You Answer

• Verify which choice is on the suction side of rotating machinery (where vacuum can occur). • Eliminate any options that normally see only positive pressure in normal operation. • Confirm that the remaining option is a place where an operator needs to monitor both vacuum and pressure on a single instrument.