What type of pressure do manifold gauges measure?

Manifold gauges are designed to measure pressure in relation to a known point, specifically atmospheric pressure. This means they can measure both positive pressure (gauges that display above atmospheric pressure) and negative pressure (often referred to as vacuum). By comparing the pressure within a system or a refrigerant to the surrounding atmospheric pressure, manifold gauges provide critical information about the operating conditions of HVAC systems, refrigeration units, or any system under pressure. This ability to indicate pressure relative to a reference point is essential for diagnosing and adjusting system performance accurately. In contrast to other options, which either limit the measurement to positive or negative pressure specifically or refer to adjustments rather than measurement, the function of measuring pressure against a known baseline distinguishes manifold gauges in their usage and application.