What type of gauge is used to measure pressure above and below atmosphere?

The compound gauge is designed to measure both pressures above atmospheric pressure (gauge pressure) and pressures below atmospheric pressure (vacuum). This functionality is essential in various HVAC and refrigeration applications where knowing both types of pressure is critical for system performance.

A compound gauge usually displays a range that includes both negative and positive values relative to atmospheric pressure, which is particularly useful for technicians who need to monitor the performance of refrigeration systems as they operate under different conditions.

In contrast, absolute gauges only measure pressure relative to a perfect vacuum, ignoring atmospheric pressure entirely, while digital gauges can display different types of pressure but do not have the specific functionality to measure both above and below atmospheric pressure simultaneously. Manometers measure pressure using fluid columns and can indicate both gauge and absolute pressure but are often less convenient for various applications compared to compound gauges.