A Bourdon tube is primarily used to measure which of the following?

The Bourdon tube is a widely recognized instrument specifically designed to measure pressure. It operates based on the principle that a change in pressure causes the tube to deform, which consequently leads to the movement of a pointer across a calibrated scale. This mechanism allows for a visual representation of pressure readings, making it particularly useful in various applications, from industrial environments to HVAC systems.

In contrast, instruments for measuring flow rate, temperature, and humidity utilize entirely different mechanisms and designs tailored to their respective measurement requirements. For instance, flow rate is typically measured using flow meters, temperature is gauged with thermometers, and humidity is assessed with hygrometers. Each of these tools functions in a way that aligns with the specific physical properties they are designed to measure, which is distinct from the pressure sensing capabilities of the Bourdon tube.