What type of reading does a compound pressure gauge provide?

A compound pressure gauge is designed to measure both pressure and vacuum within a system. This dual functionality is essential for applications where it's important to monitor a system that might operate both above and below atmospheric pressure.

In practical terms, a compound gauge can display pressure readings in psi (pounds per square inch) in the positive range and vacuum readings in inches of mercury (inHg) or another vacuum measurement unit in the negative range. This capability allows technicians to assess the performance of refrigeration and air conditioning systems more comprehensively, as they often encounter situations where both conditions need to be monitored, such as during the evacuation of a system or when checking refrigerant levels.

The other options focus solely on either pressure or vacuum, or they include temperature, which are not applicable in this context. A compound gauge integrates both measurements into one device, making it versatile and crucial for proper diagnostics and system evaluations in HVAC fields.