In industries, Liquid levels are measured either directly or indirectly. In direct method level can be measured by using indicators such as dipsticks, floats, and gauge glasses. Where as in indirect method, it is measured using static or differential pressure instruments. Normally Direct measurements are used only for local indication, meanwhile Indirect measurements are used to provide both remote indication and a control signal.
Direct method
Direct methods are used only for monitoring or getting indications locally. Even though in industries, it is used for various reasons on many types of substances. There are different types of instruments for this purposes. Some of them are discussed below.
1. Dipsticks
A dipstick is a rod used to measure the level of fluid in a tank. This rod may or may not be marked the level units and Level is measured by observing the wetted portion of the rod. In power plants, Dipsticks are commonly used for measuring level of fuel oil and lub oil in tanks.
dip stick
2. Floats
Floats are motion balance devices which will ride on the surface of a liquid and follow the level changes. They can be connected to level indicators in many ways, such as a lever arm connected to a pointer to indicate level on a scale. Another method is to connect a weighted line to the float. This weighted line is passed throug the top of the tank, and the weight indicates the level on the side of the tank. Floats are commonly used on both oil and water storage tanks. In this cases float must have lesser density compared to the substance of interest and must not react with substance or undergo corrosion.
float
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