What do low side (compound) gauges measure?

Low side (compound) gauges are designed to measure both pressure above atmospheric levels and vacuum levels below atmospheric pressure. This capability makes them versatile tools in various applications, particularly in HVAC and refrigeration systems where precise monitoring of refrigerant pressures is crucial for efficient operation.

Measuring above atmospheric pressure allows the gauge to provide readings when the system is under normal operational conditions, while measuring below atmospheric pressure enables the detection of vacuum levels during system evacuation or during the low-pressure side operation of a refrigeration cycle. By encompassing both ranges, low side gauges offer a comprehensive view of the conditions within the system, allowing technicians to make informed decisions.

In contrast, the other options are limited in scope: some only address high pressure, or focus solely on either above or below atmospheric pressures, making them less applicable for systems that experience a range of pressures.