Understanding Vacuum Measurement with Compound Gauges

What is the purpose of a compound gauge in vacuum measurement?

A. To measure absolute pressure accurately

B. To measure negative pressure relative to atmospheric pressure

C. To indicate system evacuation status

D. To determine pressure in a closed system

Answer:

B. To measure negative pressure relative to atmospheric pressure

In vacuum measurement, a compound gauge serves the purpose of measuring both negative pressure (vacuum) and positive pressure relative to atmospheric pressure. It is designed to provide readings that are relative to the atmospheric pressure, allowing for a holistic view of the pressure within a system.

When using a compound gauge, it is essential to understand that it does not measure absolute pressure accurately. Instead, it focuses on the pressure differential from the atmosphere. This characteristic makes it suitable for applications where the distinction between positive and negative pressure is important, such as in systems that alternate between vacuum and pressure conditions.

Although a compound gauge cannot indicate when a system is properly evacuated due to its reliance on gauge pressure relative to atmospheric pressure, it is still valuable in providing insights into the pressure dynamics within a closed system. To determine the effectiveness of system evacuation, an absolute pressure gauge is required for precise vacuum measurements.