What is essential for tanks gauges to detect?

The primary function of tank gauges is to accurately measure and detect changes in the level of the liquid within the tank. Specifically, detecting small changes in pressure is crucial because these changes can indicate fluctuations in the liquid level, which is vital for monitoring and managing the contents of the tank effectively.

When liquid is drawn from or added to the tank, the pressure at the gauge will change even if the volume variation is minimal. The ability to detect these small changes allows operators to maintain the integrity of the system, ensure safety, and adhere to regulatory requirements.

The other options relate to different measurements that may not always be directly relevant to the primary function of tank gauges. For instance, high pressure can indicate an issue, but relying solely on high pressure readings does not provide comprehensive insight into the tank's contents. Large fluctuations in volume may not be frequent or manageable in a well-functioning tank system, and temperature changes, while important in some contexts, do not directly relate to the functionality of gauges meant for level detection.