Which of the following factors directly influences the gauge pressure reading?

The gauge pressure reading is directly influenced by atmospheric pressure changes because gauge pressure is defined as the pressure relative to atmospheric pressure. It measures the pressure of a fluid above the ambient air pressure. Therefore, when atmospheric pressure changes, it impacts the baseline from which the gauge measures pressure.

For example, if the atmospheric pressure increases, a gauge will read lower for a given pressure in a system since it is working relative to this higher baseline. On the other hand, if atmospheric pressure decreases, the gauge will indicate a higher pressure for the same amount of fluid pressure because it’s measuring above a lower baseline. Understanding this relationship is crucial for interpreting gauge pressure readings accurately in various conditions, particularly in refrigeration systems where pressure readings are essential for system performance and safety.

The other factors mentioned, while they may relate to pressure in different contexts, do not directly influence gauge pressure readings in the same manner. Fluid density and temperature variations are more related to the properties of the fluid itself, whereas high elevations can affect absolute pressure measurements but the gauge pressure measuring instrument remains unaffected by elevation changes since it is designed to read pressure relative to the surrounding atmospheric conditions.