Which instrument measures the absolute pressure of the atmosphere using a spring action balanced against the air above?

The aneroid barometer is specifically designed to measure the absolute pressure of the atmosphere using a system of flexible metal capsules, often referred to as aneroids. These capsules expand and contract in response to changes in atmospheric pressure, and this motion is translated into a readable measurement on a dial or scale.

The functionality of the aneroid barometer is based on the principle of balancing the pressure of the air above with the mechanical pressure exerted by the spring action in the capsule. This allows for a practical and compact device that can provide accurate atmospheric pressure readings without the need for liquid, which is common in other types of barometers.

While the term "aneroid" could refer to various instruments that utilize this technology, the specificity of "aneroid barometer" clearly indicates its primary role as a pressure measuring device. Other options may involve aspects of pressure measurement, but none match the detailed description and function of the aneroid barometer in measuring absolute pressure in the atmosphere.