What information does a fixed liquid level gauge communicate?

A fixed liquid level gauge is designed specifically to indicate the height of the liquid within a container relative to a fixed reference point. This guide provides crucial information about the liquid level, which is essential for ensuring safe operation when storing and handling liquids. By communicating the vapor space within the container, a fixed liquid level gauge allows operators to understand how much space is above the liquid. This helps in assessing the available volume for any vapors and is important for maintaining safe pressure levels and preventing overflow or leaks.

The other choices, such as gas purity, temperature of the liquid, and flow rate, are not directly indicated by a fixed liquid level gauge. Gas purity would require different methods of analysis, temperature measurements would typically be taken using thermometers, and flow rate would necessitate flow meters or similar devices. Thus, the primary function of a fixed liquid level gauge remains focused on conveying the extent of vapor space above the liquid.