What is NOT included in the measurement of liquid levels?

The correct answer pertains to the nature of liquid level measurement techniques. Pressure transducers are primarily used to measure pressure exerted by a liquid column, which can help infer liquid levels, but they are not direct instruments for measuring the liquid level itself. In contrast, floats and probes, as well as weirs and flumes, are methods specifically designed to measure liquid levels directly. V-notch weirs are specialized types of weirs that also directly measure flow rates but can be associated with liquid level measurements as part of fluid management. Therefore, while pressure transducers are integral to many liquid measurement systems, they do not directly measure liquid levels like the other options listed.