|-sight glass，sight window，view port
we provides a means of seeing inside a process vessel or tank. Operators use sight glasses to visually verify stages of a process, inspect process media, and to observe liquid levels.
-Sight flow indicators，Flow Switches
Sight flow indicators is a device installed into a pipe to provide a visual of verifying liquid flow for direction and accurate flow rate. Sight flow indicators allow operators to observe the color and clarity of liquids through a window. A sight flow indicator is a body with one or more viewing windows, usually with gaskets, and a way to mount the indicator to the pipeline, such as flanged, threaded, or sanitary clamp connections
-Liquid level gauges
are industrial meters that are used to determine the level of a liquid in a process tank. Liquid level gauge calibration is used to ensure proper readings are obtained when using level gauges