A bourdon tube is found inside of a ______.

A bourdon tube is a mechanical device commonly used in pressure gauges to measure the pressure of gases or liquids. The bourdon tube is a curved, spring-like tube that straightens out when pressure is applied. As the internal pressure increases, the tube straightens, and this movement is translated into a needle reading on the gauge's dial. This mechanism allows for accurate pressure measurement, making it a critical component in many applications where monitoring pressure is essential.

In contrast, flow meters measure the flow rate of fluids, and while they may have various designs, they typically do not incorporate a bourdon tube. Thermometers are designed to measure temperature, using different principles such as thermal expansion of liquids or changes in electrical resistance rather than pressure measurement. Hygrometers measure humidity levels in the air and do not involve pressure measurement either, as their function is entirely focused on moisture content detection.

Thus, the presence of a bourdon tube is specifically associated with pressure gauges, confirming that pressure measurement is the context in which this device is utilized.