Which type of gauge is calibrated to read both positive and negative pressure?

A compound gauge is specifically designed to measure both positive pressure and negative pressure (vacuum). This feature allows it to provide readings in a range that includes both the atmospheric pressure above a zero reference point (positive pressure) and below that reference (vacuum).

In many applications, particularly in firefighting and industrial settings, the ability to monitor both sides of this spectrum is essential. For instance, fire apparatus may need to assess pressure within hoses and systems where not only are pressurized fluids important, but understanding vacuum conditions can also be critical, such as when ensuring adequate suction from a water source.

The other types of gauges mentioned serve more specialized functions. A pressure gauge typically measures only positive pressure. A vacuum gauge is solely focused on measuring negative pressure but does not provide positive pressure readings. A flow gauge measures the rate at which a fluid passes through a system, which does not relate to pressure measurement at all. Therefore, the compound gauge stands out for its versatility in measuring both states of pressure.